...

20 files changed, 1531 insertions, 863 deletions

diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/FilterComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/FilterComputation.java
index 9781e6f..1150b92 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/FilterComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/FilterComputation.java
@@ -44,7 +44,6 @@ public class FilterComputation extends GenericComputation
       final Computation lambda_function;
       final Computation collection;
       final List<Computation> extra_params;
-      final List<Type> signature;
 
       if (call_parameters.size() < 2)
       {
@@ -56,61 +55,31 @@ public class FilterComputation extends GenericComputation
 
       lambda_function = call_parameters.get(0);
       collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
 
-      if (call_parameters.size() == 2)
-      {
-         extra_params = new ArrayList<Computation>();
-      }
-      else
-      {
-         extra_params = call_parameters.subList(2, call_parameters.size());
-      }
-
-      lambda_function.expect_non_string();
       collection.expect_non_string();
 
-      RecurrentChecks.assert_is_a_lambda_function(lambda_function);
-
-      signature = ((LambdaType) lambda_function.get_type()).get_signature();
-
-      if (signature.size() < 1)
-      {
-         // TODO: Error.
-         System.err.println
-         (
-            "Lambda signature too small at "
-            + lambda_function.get_origin().toString()
-         );
-
-         return null;
-      }
-
-      if (signature.size() > 2)
-      {
-         RecurrentChecks.propagate_expected_types_and_assert_computations_matches_signature
-         (
-            origin,
-            extra_params,
-            signature.subList(1, signature.size())
-         );
-      }
-
       if (alias.startsWith("set:"))
       {
-         RecurrentChecks.assert_is_a_set_of(collection, signature.get(0));
+         RecurrentChecks.assert_is_a_set(collection);
       }
       else
       {
-         RecurrentChecks.assert_is_a_list_of(collection, signature.get(0));
+         RecurrentChecks.assert_is_a_list(collection);
       }
 
-      RecurrentChecks.assert_can_be_used_as
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
-         lambda_function.get_origin(),
-         ((LambdaType) lambda_function.get_type()).get_return_type(),
-         Type.BOOL
+         lambda_function,
+         Collections.singletonList
+         (
+            ((CollectionType) collection.get_type()).get_content_type()
+         ),
+         extra_params
       );
 
+      RecurrentChecks.assert_return_type_is(lambda_function, Type.BOOL);
+
       return
          new FilterComputation
          (
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedFilterComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedFilterComputation.java
index 8a2bf4f..e6d8469 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedFilterComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedFilterComputation.java
@@ -46,34 +46,51 @@ public class IndexedFilterComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection = null;
-      final List<Computation> extra_params = null;
-      final List<Type> target_signature;
+      final Computation lambda_function;
+      final Computation collection;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
 
-      target_signature = new ArrayList<Type>();
+      base_param_types = new ArrayList<Type>();
+      base_param_types.add(Type.INT);
 
-      RecurrentChecks.assert_is_a_collection(collection);
+      if (call_parameters.size() < 2)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
 
-      target_signature.add(Type.INT);
-      target_signature.add
-      (
-         ((CollectionType) collection.get_type()).get_content_type()
-      );
+         return null;
+      }
 
-      for (final Computation c: extra_params)
+      lambda_function = call_parameters.get(0);
+      collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
+
+      collection.expect_non_string();
+
+      if (alias.startsWith("set:"))
       {
-         target_signature.add(c.get_type());
+         RecurrentChecks.assert_is_a_set(collection);
+      }
+      else
+      {
+         RecurrentChecks.assert_is_a_list(collection);
       }
 
-      RecurrentChecks.assert_lambda_matches_types
+      base_param_types.add
+      (
+         ((CollectionType) collection.get_type()).get_content_type()
+      );
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
          lambda_function,
-         Type.BOOL,
-         target_signature
+         base_param_types,
+         extra_params
       );
 
+      RecurrentChecks.assert_return_type_is(lambda_function, Type.BOOL);
+
       return
          new IndexedFilterComputation
          (
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMapComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMapComputation.java
index a0adf57..b9057fe 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMapComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMapComputation.java
@@ -46,28 +46,48 @@ public class IndexedMapComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection = null;
-      final List<Computation> extra_params = null;
-      final List<Type> in_types;
+      final Computation lambda_function;
+      final Computation collection;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
 
-      in_types = new ArrayList<Type>();
+      base_param_types = new ArrayList<Type>();
+      base_param_types.add(Type.INT);
 
-      RecurrentChecks.assert_is_a_collection(collection);
+      if (call_parameters.size() < 2)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
 
-      in_types.add(Type.INT);
-      in_types.add
-      (
-         ((CollectionType) collection.get_type()).get_content_type()
-      );
+         return null;
+      }
 
-      for (final Computation c: extra_params)
+      lambda_function = call_parameters.get(0);
+      collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
+
+      collection.expect_non_string();
+
+      if (alias.startsWith("set:"))
       {
-         in_types.add(c.get_type());
+         RecurrentChecks.assert_is_a_set(collection);
       }
+      else
+      {
+         RecurrentChecks.assert_is_a_list(collection);
+      }
+
+      base_param_types.add
+      (
+         ((CollectionType) collection.get_type()).get_content_type()
+      );
 
-      RecurrentChecks.assert_lambda_matches_types(lambda_function, in_types);
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
+      (
+         lambda_function,
+         base_param_types,
+         extra_params
+      );
 
       return
          new IndexedMapComputation
@@ -80,7 +100,7 @@ public class IndexedMapComputation extends GenericComputation
             (
                origin,
                ((LambdaType) lambda_function.get_type()).get_return_type(),
-               ((CollectionType) collection.get_type()).is_set(),
+               false,
                "auto generated"
             )
          );
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMergeComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMergeComputation.java
index c90540d..f65e581 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMergeComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedMergeComputation.java
@@ -35,24 +35,6 @@ public class IndexedMergeComputation extends GenericComputation
       aliases.add("set:indexedMerge");
       aliases.add("set:imerge");
 
-      aliases.add("list:indexed_safe_merge");
-      aliases.add("list:indexedsafemerge");
-      aliases.add("list:indexedSafeMerge");
-      aliases.add("list:isafemerge");
-      aliases.add("list:safe_indexed_merge");
-      aliases.add("list:safeindexedmerge");
-      aliases.add("list:safeIndexedMerge");
-      aliases.add("list:safeimerge");
-
-      aliases.add("set:indexed_safe_merge");
-      aliases.add("set:indexedsafemerge");
-      aliases.add("set:indexedSafeMerge");
-      aliases.add("set:isafemerge");
-      aliases.add("set:safe_indexed_merge");
-      aliases.add("set:safeindexedmerge");
-      aliases.add("set:safeIndexedMerge");
-      aliases.add("set:safeimerge");
-
       return aliases;
    }
 
@@ -64,81 +46,68 @@ public class IndexedMergeComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection_in_a = null;
-      final Computation default_a = null;
-      final Computation collection_in_b = null;
-      final Computation default_b = null;
-      final boolean to_set = false;
-      final List<Computation> extra_params = null;
-      final List<Type> types_in;
-
-      types_in = new ArrayList<Type>();
-
-      if (default_a == null)
-      {
-         RecurrentChecks.assert_is_a_collection(collection_in_a);
-      }
-      else
-      {
-         RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
-         (
-            collection_in_a,
-            default_a
-         );
-      }
+      final Computation lambda_function;
+      final Computation collection_a;
+      final Computation collection_b;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
+      final boolean to_set;
 
-      if (default_b == null)
-      {
-         RecurrentChecks.assert_is_a_collection(collection_in_b);
-      }
-      else
+      base_param_types = new ArrayList<Type>();
+
+      if (call_parameters.size() < 3)
       {
-         RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
-         (
-            collection_in_b,
-            default_b
-         );
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
+
+         return null;
       }
 
-      types_in.add(Type.INT);
+      lambda_function = call_parameters.get(0);
+      collection_a = call_parameters.get(1);
+      collection_b = call_parameters.get(2);
+      extra_params = call_parameters.subList(3, call_parameters.size());
 
-      types_in.add
+      collection_a.expect_non_string();
+      collection_b.expect_non_string();
+
+      base_param_types.add(Type.INT);
+
+      base_param_types.add
       (
-         ((CollectionType) collection_in_a.get_type()).get_content_type()
+         ((CollectionType) collection_a.get_type()).get_content_type()
       );
 
-      if (default_b != null)
-      {
-         /*
-          * Safe-Mode: two indices.
-          * Unsafe-Mode: only one index, since out-of-bound means stopping.
-          */
-         types_in.add(Type.INT);
-      }
+      base_param_types.add
+      (
+         ((CollectionType) collection_b.get_type()).get_content_type()
+      );
 
-      types_in.add
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
-         ((CollectionType) collection_in_b.get_type()).get_content_type()
+         lambda_function,
+         base_param_types,
+         extra_params
       );
 
-      for (final Computation c: extra_params)
+      to_set = alias.startsWith("set:");
+
+      if (to_set)
       {
-         types_in.add(c.get_type());
+         RecurrentChecks.assert_can_be_used_in_set
+         (
+            lambda_function.get_origin().with_hint("returned type"),
+            ((LambdaType) lambda_function.get_type()).get_return_type()
+         );
       }
 
-      RecurrentChecks.assert_lambda_matches_types(lambda_function, types_in);
-
       return
          new IndexedMergeComputation
          (
             origin,
             lambda_function,
-            collection_in_a,
-            default_a,
-            collection_in_b,
-            default_b,
+            collection_a,
+            collection_b,
             to_set,
             extra_params,
             CollectionType.build
@@ -157,9 +126,7 @@ public class IndexedMergeComputation extends GenericComputation
    protected final List<Computation> extra_params;
    protected final Computation lambda_function;
    protected final Computation collection_in_a;
-   protected final Computation default_a;
    protected final Computation collection_in_b;
-   protected final Computation default_b;
    protected final boolean to_set;
 
    /***************************************************************************/
@@ -171,9 +138,7 @@ public class IndexedMergeComputation extends GenericComputation
       final Origin origin,
       final Computation lambda_function,
       final Computation collection_in_a,
-      final Computation default_a,
       final Computation collection_in_b,
-      final Computation default_b,
       final boolean to_set,
       final List<Computation> extra_params,
       final Type output_type
@@ -183,9 +148,7 @@ public class IndexedMergeComputation extends GenericComputation
 
       this.lambda_function = lambda_function;
       this.collection_in_a = collection_in_a;
-      this.default_a = default_a;
       this.collection_in_b = collection_in_b;
-      this.default_b = default_b;
       this.to_set = to_set;
       this.extra_params = extra_params;
    }
@@ -204,21 +167,11 @@ public class IndexedMergeComputation extends GenericComputation
       return collection_in_a;
    }
 
-   public Computation get_default_a ()
-   {
-      return default_a;
-   }
-
    public Computation get_collection_in_b ()
    {
       return collection_in_b;
    }
 
-   public Computation get_default_b ()
-   {
-      return default_b;
-   }
-
    public List<Computation> get_extra_parameters ()
    {
       return extra_params;
@@ -249,27 +202,7 @@ public class IndexedMergeComputation extends GenericComputation
       sb.append(collection_in_a.toString());
       sb.append(" ");
 
-      if (default_a == null)
-      {
-         sb.append("null");
-      }
-      else
-      {
-         sb.append(default_a.toString());
-      }
-
-      sb.append(" ");
       sb.append(collection_in_b.toString());
-      sb.append(" ");
-
-      if (default_b == null)
-      {
-         sb.append("null");
-      }
-      else
-      {
-         sb.append(default_b.toString());
-      }
 
       for (final Computation c: extra_params)
       {
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedSafeMergeComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedSafeMergeComputation.java
new file mode 100644
index 0000000..dc860f6
--- /dev/null
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/IndexedSafeMergeComputation.java
@@ -0,0 +1,288 @@
+package tonkadur.fate.v1.lang.computation.generic;
+
+import java.util.Collection;
+import java.util.ArrayList;
+import java.util.List;
+
+import tonkadur.parser.Origin;
+import tonkadur.parser.ParsingError;
+
+import tonkadur.fate.v1.lang.type.Type;
+import tonkadur.fate.v1.lang.type.LambdaType;
+import tonkadur.fate.v1.lang.type.CollectionType;
+
+import tonkadur.fate.v1.lang.meta.ComputationVisitor;
+import tonkadur.fate.v1.lang.meta.Computation;
+import tonkadur.fate.v1.lang.meta.Computation;
+import tonkadur.fate.v1.lang.meta.RecurrentChecks;
+
+import tonkadur.fate.v1.lang.computation.GenericComputation;
+
+public class IndexedSafeMergeComputation extends GenericComputation
+{
+   public static Collection<String> get_aliases ()
+   {
+      final Collection<String> aliases;
+
+      aliases = new ArrayList<String>();
+
+      aliases.add("list:indexed_merge");
+      aliases.add("list:indexedmerge");
+      aliases.add("list:indexedMerge");
+      aliases.add("list:imerge");
+      aliases.add("set:indexed_merge");
+      aliases.add("set:indexedmerge");
+      aliases.add("set:indexedMerge");
+      aliases.add("set:imerge");
+
+      aliases.add("list:indexed_safe_merge");
+      aliases.add("list:indexedsafemerge");
+      aliases.add("list:indexedSafeMerge");
+      aliases.add("list:isafemerge");
+      aliases.add("list:safe_indexed_merge");
+      aliases.add("list:safeindexedmerge");
+      aliases.add("list:safeIndexedSafeMerge");
+      aliases.add("list:safeimerge");
+
+      aliases.add("set:indexed_safe_merge");
+      aliases.add("set:indexedsafemerge");
+      aliases.add("set:indexedSafeMerge");
+      aliases.add("set:isafemerge");
+      aliases.add("set:safe_indexed_merge");
+      aliases.add("set:safeindexedmerge");
+      aliases.add("set:safeIndexedSafeMerge");
+      aliases.add("set:safeimerge");
+
+      return aliases;
+   }
+
+   public static Computation build
+   (
+      final Origin origin,
+      final String alias,
+      final List<Computation> call_parameters
+   )
+   throws Throwable
+   {
+      final Computation lambda_function;
+      final Computation collection_a;
+      final Computation default_a;
+      final Computation collection_b;
+      final Computation default_b;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
+      final boolean to_set;
+
+      base_param_types = new ArrayList<Type>();
+
+      if (call_parameters.size() < 5)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
+
+         return null;
+      }
+
+      lambda_function = call_parameters.get(0);
+      collection_a = call_parameters.get(1);
+      default_a = call_parameters.get(2);
+      collection_b = call_parameters.get(3);
+      default_b = call_parameters.get(4);
+      extra_params = call_parameters.subList(5, call_parameters.size());
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
+      (
+         collection_a,
+         default_a
+      );
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
+      (
+         collection_a,
+         default_b
+      );
+
+      base_param_types.add(Type.INT);
+
+      base_param_types.add
+      (
+         ((CollectionType) collection_a.get_type()).get_content_type()
+      );
+
+      base_param_types.add(Type.INT);
+
+      base_param_types.add
+      (
+         ((CollectionType) collection_b.get_type()).get_content_type()
+      );
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
+      (
+         lambda_function,
+         base_param_types,
+         extra_params
+      );
+
+      to_set = alias.startsWith("set:");
+
+      if (to_set)
+      {
+         RecurrentChecks.assert_can_be_used_in_set
+         (
+            lambda_function.get_origin().with_hint("returned value"),
+            ((LambdaType) lambda_function.get_type()).get_return_type()
+         );
+      }
+
+      return
+         new IndexedSafeMergeComputation
+         (
+            origin,
+            lambda_function,
+            collection_a,
+            default_a,
+            collection_b,
+            default_b,
+            to_set,
+            extra_params,
+            CollectionType.build
+            (
+               origin,
+               ((LambdaType) lambda_function.get_type()).get_return_type(),
+               to_set,
+               "auto generated"
+            )
+         );
+   }
+
+   /***************************************************************************/
+   /**** MEMBERS **************************************************************/
+   /***************************************************************************/
+   protected final List<Computation> extra_params;
+   protected final Computation lambda_function;
+   protected final Computation collection_in_a;
+   protected final Computation default_a;
+   protected final Computation collection_in_b;
+   protected final Computation default_b;
+   protected final boolean to_set;
+
+   /***************************************************************************/
+   /**** PROTECTED ************************************************************/
+   /***************************************************************************/
+   /**** Constructors *********************************************************/
+   protected IndexedSafeMergeComputation
+   (
+      final Origin origin,
+      final Computation lambda_function,
+      final Computation collection_in_a,
+      final Computation default_a,
+      final Computation collection_in_b,
+      final Computation default_b,
+      final boolean to_set,
+      final List<Computation> extra_params,
+      final Type output_type
+   )
+   {
+      super(origin, output_type);
+
+      this.lambda_function = lambda_function;
+      this.collection_in_a = collection_in_a;
+      this.default_a = default_a;
+      this.collection_in_b = collection_in_b;
+      this.default_b = default_b;
+      this.to_set = to_set;
+      this.extra_params = extra_params;
+   }
+
+   /***************************************************************************/
+   /**** PUBLIC ***************************************************************/
+   /***************************************************************************/
+   /**** Accessors ************************************************************/
+   public Computation get_lambda_function ()
+   {
+      return lambda_function;
+   }
+
+   public Computation get_collection_in_a ()
+   {
+      return collection_in_a;
+   }
+
+   public Computation get_default_a ()
+   {
+      return default_a;
+   }
+
+   public Computation get_collection_in_b ()
+   {
+      return collection_in_b;
+   }
+
+   public Computation get_default_b ()
+   {
+      return default_b;
+   }
+
+   public List<Computation> get_extra_parameters ()
+   {
+      return extra_params;
+   }
+
+   public boolean to_set ()
+   {
+      return to_set;
+   }
+
+   /**** Misc. ****************************************************************/
+   @Override
+   public String toString ()
+   {
+      final StringBuilder sb = new StringBuilder();
+
+      if (to_set)
+      {
+         sb.append("(IndexedSafeMergeToSet ");
+      }
+      else
+      {
+         sb.append("(IndexedSafeMergeToList ");
+      }
+
+      sb.append(lambda_function.toString());
+      sb.append(" ");
+      sb.append(collection_in_a.toString());
+      sb.append(" ");
+
+      if (default_a == null)
+      {
+         sb.append("null");
+      }
+      else
+      {
+         sb.append(default_a.toString());
+      }
+
+      sb.append(" ");
+      sb.append(collection_in_b.toString());
+      sb.append(" ");
+
+      if (default_b == null)
+      {
+         sb.append("null");
+      }
+      else
+      {
+         sb.append(default_b.toString());
+      }
+
+      for (final Computation c: extra_params)
+      {
+         sb.append(" ");
+         sb.append(c.toString());
+      }
+
+      sb.append(")");
+
+      return sb.toString();
+   }
+}
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/MapComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/MapComputation.java
index 4fcf324..a62e14c 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/MapComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/MapComputation.java
@@ -41,30 +41,41 @@ public class MapComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection = null;
-      final List<Computation> extra_params = null;
-      final List<Type> target_signature;
+      final Computation lambda_function;
+      final Computation collection;
+      final List<Computation> extra_params;
 
-      target_signature = new ArrayList<Type>();
+      if (call_parameters.size() < 2)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
 
-      RecurrentChecks.assert_is_a_collection(collection);
+         return null;
+      }
 
-      target_signature.add
-      (
-         ((CollectionType) collection.get_type()).get_content_type()
-      );
+      lambda_function = call_parameters.get(0);
+      collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
 
-      for (final Computation c: extra_params)
+      collection.expect_non_string();
+
+      if (alias.startsWith("set:"))
+      {
+         RecurrentChecks.assert_is_a_set(collection);
+      }
+      else
       {
-         target_signature.add(c.get_type());
+         RecurrentChecks.assert_is_a_list(collection);
       }
 
-      RecurrentChecks.assert_lambda_matches_types
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
          lambda_function,
-         target_signature
+         Collections.singletonList
+         (
+            ((CollectionType) collection.get_type()).get_content_type()
+         ),
+         extra_params
       );
 
       return
@@ -78,7 +89,7 @@ public class MapComputation extends GenericComputation
             (
                origin,
                ((LambdaType) lambda_function.get_type()).get_return_type(),
-               ((CollectionType) collection.get_type()).is_set(),
+               false,
                "auto generated"
             )
          );
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/MergeComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/MergeComputation.java
index 3ebe675..287957d 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/MergeComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/MergeComputation.java
@@ -27,13 +27,7 @@ public class MergeComputation extends GenericComputation
       aliases = new ArrayList<String>();
 
       aliases.add("list:merge");
-      aliases.add("list:safe_merge");
-      aliases.add("list:safemerge");
-      aliases.add("list:safeMerge");
       aliases.add("set:merge");
-      aliases.add("set:safe_merge");
-      aliases.add("set:safemerge");
-      aliases.add("set:safeMerge");
 
       return aliases;
    }
@@ -46,70 +40,66 @@ public class MergeComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection_in_a = null;
-      final Computation default_a = null;
-      final Computation collection_in_b = null;
-      final Computation default_b = null;
-      final boolean to_set = false;
-      final List<Computation> extra_params = null;
-      final List<Type> types_in;
-
-      types_in = new ArrayList<Type>();
-
-      if (default_a == null)
-      {
-         RecurrentChecks.assert_is_a_collection(collection_in_a);
-      }
-      else
-      {
-         RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
-         (
-            collection_in_a,
-            default_a
-         );
-      }
+      final Computation lambda_function;
+      final Computation collection_a;
+      final Computation collection_b;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
+      final boolean to_set;
 
-      if (default_b == null)
-      {
-         RecurrentChecks.assert_is_a_collection(collection_in_b);
-      }
-      else
+      base_param_types = new ArrayList<Type>();
+
+      if (call_parameters.size() < 3)
       {
-         RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
-         (
-            collection_in_b,
-            default_b
-         );
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
+
+         return null;
       }
 
-      types_in.add
+      lambda_function = call_parameters.get(0);
+      collection_a = call_parameters.get(1);
+      collection_b = call_parameters.get(2);
+      extra_params = call_parameters.subList(3, call_parameters.size());
+
+      collection_a.expect_non_string();
+      collection_b.expect_non_string();
+
+      base_param_types.add
       (
-         ((CollectionType) collection_in_a.get_type()).get_content_type()
+         ((CollectionType) collection_a.get_type()).get_content_type()
       );
 
-      types_in.add
+      base_param_types.add
       (
-         ((CollectionType) collection_in_b.get_type()).get_content_type()
+         ((CollectionType) collection_b.get_type()).get_content_type()
       );
 
-      for (final Computation c: extra_params)
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
+      (
+         lambda_function,
+         base_param_types,
+         extra_params
+      );
+
+      to_set = alias.startsWith("set:");
+
+      if (to_set)
       {
-         types_in.add(c.get_type());
+         RecurrentChecks.assert_can_be_used_in_set
+         (
+            lambda_function.get_origin().with_hint("returned value"),
+            ((LambdaType) lambda_function.get_type()).get_return_type()
+         );
       }
 
-      RecurrentChecks.assert_lambda_matches_types(lambda_function, types_in);
-
       return
          new MergeComputation
          (
             origin,
             lambda_function,
-            collection_in_a,
-            default_a,
-            collection_in_b,
-            default_b,
+            collection_a,
+            collection_b,
             to_set,
             extra_params,
             CollectionType.build
@@ -127,9 +117,7 @@ public class MergeComputation extends GenericComputation
    protected final List<Computation> extra_params;
    protected final Computation lambda_function;
    protected final Computation collection_in_a;
-   protected final Computation default_a;
    protected final Computation collection_in_b;
-   protected final Computation default_b;
    protected final boolean to_set;
 
    /***************************************************************************/
@@ -141,9 +129,7 @@ public class MergeComputation extends GenericComputation
       final Origin origin,
       final Computation lambda_function,
       final Computation collection_in_a,
-      final Computation default_a,
       final Computation collection_in_b,
-      final Computation default_b,
       final boolean to_set,
       final List<Computation> extra_params,
       final Type output_type
@@ -153,9 +139,7 @@ public class MergeComputation extends GenericComputation
 
       this.lambda_function = lambda_function;
       this.collection_in_a = collection_in_a;
-      this.default_a = default_a;
       this.collection_in_b = collection_in_b;
-      this.default_b = default_b;
       this.to_set = to_set;
       this.extra_params = extra_params;
    }
@@ -174,21 +158,11 @@ public class MergeComputation extends GenericComputation
       return collection_in_a;
    }
 
-   public Computation get_default_a ()
-   {
-      return default_a;
-   }
-
    public Computation get_collection_in_b ()
    {
       return collection_in_b;
    }
 
-   public Computation get_default_b ()
-   {
-      return default_b;
-   }
-
    public List<Computation> get_extra_parameters ()
    {
       return extra_params;
@@ -219,27 +193,7 @@ public class MergeComputation extends GenericComputation
       sb.append(collection_in_a.toString());
       sb.append(" ");
 
-      if (default_a == null)
-      {
-         sb.append("null");
-      }
-      else
-      {
-         sb.append(default_a.toString());
-      }
-
-      sb.append(" ");
       sb.append(collection_in_b.toString());
-      sb.append(" ");
-
-      if (default_b == null)
-      {
-         sb.append("null");
-      }
-      else
-      {
-         sb.append(default_b.toString());
-      }
 
       for (final Computation c: extra_params)
       {
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/PartitionComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/PartitionComputation.java
index 9444bc1..34c0ca3 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/PartitionComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/PartitionComputation.java
@@ -41,34 +41,46 @@ public class PartitionComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection = null;
-      final List<Computation> extra_params = null;
+      final Computation lambda_function;
+      final Computation collection;
+      final List<Computation> extra_params;
       final Type type;
-      final List<Type> target_signature;
 
-      target_signature = new ArrayList<Type>();
+      if (call_parameters.size() < 2)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
 
-      RecurrentChecks.assert_is_a_collection(collection);
+         return null;
+      }
 
-      target_signature.add
-      (
-         ((CollectionType) collection.get_type()).get_content_type()
-      );
+      lambda_function = call_parameters.get(0);
+      collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
 
-      for (final Computation c: extra_params)
+      collection.expect_non_string();
+
+      if (alias.startsWith("set:"))
+      {
+         RecurrentChecks.assert_is_a_set(collection);
+      }
+      else
       {
-         target_signature.add(c.get_type());
+         RecurrentChecks.assert_is_a_list(collection);
       }
 
-      RecurrentChecks.assert_lambda_matches_types
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
          lambda_function,
-         Type.BOOL,
-         target_signature
+         Collections.singletonList
+         (
+            ((CollectionType) collection.get_type()).get_content_type()
+         ),
+         extra_params
       );
 
+      RecurrentChecks.assert_return_type_is(lambda_function, Type.BOOL);
+
       type =
          new ConsType
          (
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/SafeMergeComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/SafeMergeComputation.java
new file mode 100644
index 0000000..61422ac
--- /dev/null
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/SafeMergeComputation.java
@@ -0,0 +1,249 @@
+package tonkadur.fate.v1.lang.computation.generic;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import tonkadur.parser.Origin;
+import tonkadur.parser.ParsingError;
+
+import tonkadur.fate.v1.lang.type.Type;
+import tonkadur.fate.v1.lang.type.LambdaType;
+import tonkadur.fate.v1.lang.type.CollectionType;
+
+import tonkadur.fate.v1.lang.meta.ComputationVisitor;
+import tonkadur.fate.v1.lang.meta.Computation;
+import tonkadur.fate.v1.lang.meta.Computation;
+import tonkadur.fate.v1.lang.meta.RecurrentChecks;
+
+import tonkadur.fate.v1.lang.computation.GenericComputation;
+
+public class SafeMergeComputation extends GenericComputation
+{
+   public static Collection<String> get_aliases ()
+   {
+      final Collection<String> aliases;
+
+      aliases = new ArrayList<String>();
+
+      aliases.add("list:safe_merge");
+      aliases.add("list:safemerge");
+      aliases.add("list:safeMerge");
+      aliases.add("set:safe_merge");
+      aliases.add("set:safemerge");
+      aliases.add("set:safeMerge");
+
+      return aliases;
+   }
+
+   public static Computation build
+   (
+      final Origin origin,
+      final String alias,
+      final List<Computation> call_parameters
+   )
+   throws Throwable
+   {
+      final Computation lambda_function;
+      final Computation collection_a;
+      final Computation default_a;
+      final Computation collection_b;
+      final Computation default_b;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
+      final boolean to_set;
+
+      base_param_types = new ArrayList<Type>();
+
+      if (call_parameters.size() < 5)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
+
+         return null;
+      }
+
+      lambda_function = call_parameters.get(0);
+      collection_a = call_parameters.get(1);
+      default_a = call_parameters.get(2);
+      collection_b = call_parameters.get(3);
+      default_b = call_parameters.get(4);
+      extra_params = call_parameters.subList(5, call_parameters.size());
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
+      (
+         collection_a,
+         default_a
+      );
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_a_collection_of
+      (
+         collection_a,
+         default_b
+      );
+
+      base_param_types.add
+      (
+         ((CollectionType) collection_a.get_type()).get_content_type()
+      );
+
+      base_param_types.add
+      (
+         ((CollectionType) collection_b.get_type()).get_content_type()
+      );
+
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
+      (
+         lambda_function,
+         base_param_types,
+         extra_params
+      );
+
+      to_set = alias.startsWith("set:");
+
+      if (to_set)
+      {
+         RecurrentChecks.assert_can_be_used_in_set
+         (
+            lambda_function.get_origin().with_hint("returned value"),
+            ((LambdaType) lambda_function.get_type()).get_return_type()
+         );
+      }
+
+      return
+         new SafeMergeComputation
+         (
+            origin,
+            lambda_function,
+            collection_a,
+            default_a,
+            collection_b,
+            default_b,
+            to_set,
+            extra_params,
+            CollectionType.build
+            (
+               origin,
+               ((LambdaType) lambda_function.get_type()).get_return_type(),
+               to_set,
+               "auto generated"
+            )
+         );
+   }
+   /***************************************************************************/
+   /**** MEMBERS **************************************************************/
+   /***************************************************************************/
+   protected final List<Computation> extra_params;
+   protected final Computation lambda_function;
+   protected final Computation collection_in_a;
+   protected final Computation default_a;
+   protected final Computation collection_in_b;
+   protected final Computation default_b;
+   protected final boolean to_set;
+
+   /***************************************************************************/
+   /**** PROTECTED ************************************************************/
+   /***************************************************************************/
+   /**** Constructors *********************************************************/
+   protected SafeMergeComputation
+   (
+      final Origin origin,
+      final Computation lambda_function,
+      final Computation collection_in_a,
+      final Computation default_a,
+      final Computation collection_in_b,
+      final Computation default_b,
+      final boolean to_set,
+      final List<Computation> extra_params,
+      final Type output_type
+   )
+   {
+      super(origin, output_type);
+
+      this.lambda_function = lambda_function;
+      this.collection_in_a = collection_in_a;
+      this.default_a = default_a;
+      this.collection_in_b = collection_in_b;
+      this.default_b = default_b;
+      this.to_set = to_set;
+      this.extra_params = extra_params;
+   }
+
+   /***************************************************************************/
+   /**** PUBLIC ***************************************************************/
+   /***************************************************************************/
+   /**** Accessors ************************************************************/
+   public Computation get_lambda_function ()
+   {
+      return lambda_function;
+   }
+
+   public Computation get_collection_in_a ()
+   {
+      return collection_in_a;
+   }
+
+   public Computation get_default_a ()
+   {
+      return default_a;
+   }
+
+   public Computation get_collection_in_b ()
+   {
+      return collection_in_b;
+   }
+
+   public Computation get_default_b ()
+   {
+      return default_b;
+   }
+
+   public List<Computation> get_extra_parameters ()
+   {
+      return extra_params;
+   }
+
+   public boolean to_set ()
+   {
+      return to_set;
+   }
+
+   /**** Misc. ****************************************************************/
+   @Override
+   public String toString ()
+   {
+      final StringBuilder sb = new StringBuilder();
+
+      if (to_set)
+      {
+         sb.append("(SafeMergeToSet ");
+      }
+      else
+      {
+         sb.append("(SafeMergeToList ");
+      }
+
+      sb.append(lambda_function.toString());
+      sb.append(" ");
+      sb.append(collection_in_a.toString());
+      sb.append(" ");
+
+      sb.append(default_a.toString());
+
+      sb.append(" ");
+      sb.append(collection_in_b.toString());
+      sb.append(" ");
+
+      sb.append(default_b.toString());
+
+      for (final Computation c: extra_params)
+      {
+         sb.append(" ");
+         sb.append(c.toString());
+      }
+
+      sb.append(")");
+
+      return sb.toString();
+   }
+}
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/SortComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/SortComputation.java
index 64999a7..3d14dd7 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/SortComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/SortComputation.java
@@ -38,31 +38,46 @@ public class SortComputation extends GenericComputation
    )
    throws Throwable
    {
-      // TODO: implement
-      final Computation lambda_function = null;
-      final Computation collection = null;
-      final List<Computation> extra_params = null;
-      final List<Type> types_in;
+      final Computation lambda_function;
+      final Computation collection;
+      final List<Computation> extra_params;
+      final List<Type> base_param_types;
 
-      types_in = new ArrayList<Type>();
+      base_param_types = new ArrayList<Type>();
+      base_param_types.add(Type.INT);
+
+      if (call_parameters.size() < 2)
+      {
+         // TODO: Error.
+         System.err.println("Wrong number of params at " + origin.toString());
+
+         return null;
+      }
+
+      lambda_function = call_parameters.get(0);
+      collection = call_parameters.get(1);
+      extra_params = call_parameters.subList(2, call_parameters.size());
+
+      collection.expect_non_string();
 
       RecurrentChecks.assert_is_a_list(collection);
 
-      types_in.add(((CollectionType) collection.get_type()).get_content_type());
-      types_in.add(types_in.get(0));
+      base_param_types.add
+      (
+         ((CollectionType) collection.get_type()).get_content_type()
+      );
 
-      for (final Computation c: extra_params)
-      {
-         types_in.add(c.get_type());
-      }
+      base_param_types.add(base_param_types.get(0));
 
-      RecurrentChecks.assert_lambda_matches_types
+      RecurrentChecks.propagate_expected_types_and_assert_is_lambda
       (
          lambda_function,
-         Type.INT,
-         types_in
+         base_param_types,
+         extra_params
       );
 
+      RecurrentChecks.assert_return_type_is(lambda_function, Type.INT);
+
       return
          new SortComputation(origin, lambda_function, collection, extra_params);
    }
diff --git a/src/core/src/tonkadur/fate/v1/lang/meta/RecurrentChecks.java b/src/core/src/tonkadur/fate/v1/lang/meta/RecurrentChecks.java
index ae905ef..3e3c721 100644
--- a/src/core/src/tonkadur/fate/v1/lang/meta/RecurrentChecks.java
+++ b/src/core/src/tonkadur/fate/v1/lang/meta/RecurrentChecks.java
@@ -107,6 +107,27 @@ public class RecurrentChecks
       }
    }
 
+   public static void assert_can_be_used_in_set
+   (
+      final Origin o,
+      final Type t
+   )
+   throws ParsingError
+   {
+      if (!Type.COMPARABLE_TYPES.contains(t.get_act_as_type()))
+      {
+         ErrorManager.handle
+         (
+            new InvalidTypeException
+            (
+               o,
+               t,
+               Type.COMPARABLE_TYPES
+            )
+         );
+      }
+   }
+
    public static void assert_is_a_set (final Computation a)
    throws ParsingError
    {
@@ -355,6 +376,49 @@ public class RecurrentChecks
       }
    }
 
+   public static void propagate_expected_types_and_assert_is_lambda
+   (
+      final Computation lambda,
+      final List<Type> filled_types,
+      final List<Computation> extra_params
+   )
+   throws ParsingError
+   {
+      final List<Type> lambda_signature;
+      final int extra_params_size;
+
+      lambda.expect_non_string();
+
+      assert_is_a_lambda_function(lambda);
+
+      lambda_signature = ((LambdaType) lambda.get_type()).get_signature();
+
+      extra_params_size = extra_params.size();
+
+      if ((filled_types.size() + extra_params_size) != lambda_signature.size())
+      {
+         ErrorManager.handle
+         (
+            new InvalidArityException
+            (
+               lambda.get_origin(),
+               (filled_types.size() + extra_params_size),
+               lambda_signature.size(),
+               lambda_signature.size()
+            )
+         );
+      }
+
+      for (int i = filled_types.size(), j = 0; i < extra_params_size; ++i, ++j)
+      {
+         handle_expected_type_propagation
+         (
+            extra_params.get(j),
+            lambda_signature.get(i)
+         );
+      }
+   }
+
    public static void assert_types_matches_signature
    (
       final Origin o,
diff --git a/src/core/src/tonkadur/parser/Origin.java b/src/core/src/tonkadur/parser/Origin.java
index 99f1cb4..7adb310 100644
--- a/src/core/src/tonkadur/parser/Origin.java
+++ b/src/core/src/tonkadur/parser/Origin.java
@@ -6,7 +6,13 @@ public class Origin
 
    static
    {
-      BASE_LANGUAGE = new Origin(Context.BASE_LANGUAGE, Location.BASE_LANGUAGE);
+      BASE_LANGUAGE =
+         new Origin
+         (
+            Context.BASE_LANGUAGE,
+            Location.BASE_LANGUAGE,
+            "base language/core feature/mandatory inclusion"
+         );
    }
 
    /***************************************************************************/
@@ -14,6 +20,7 @@ public class Origin
    /***************************************************************************/
    protected final Context context;
    protected final Location location;
+   protected final String hint;
 
    /***************************************************************************/
    /**** PUBLIC ***************************************************************/
@@ -26,6 +33,19 @@ public class Origin
    {
       this.context = context;
       this.location = location;
+      this.hint = "";
+   }
+
+   public Origin
+   (
+      final Context context,
+      final Location location,
+      final String hint
+   )
+   {
+      this.context = context;
+      this.location = location;
+      this.hint = hint;
    }
 
    public Context get_context ()
@@ -38,6 +58,16 @@ public class Origin
       return location;
    }
 
+   public String get_hint ()
+   {
+      return hint;
+   }
+
+   public Origin with_hint (final String hint)
+   {
+      return new Origin(context.clone(), location.clone(), hint);
+   }
+
    @Override
    public String toString()
    {
@@ -46,12 +76,19 @@ public class Origin
       sb.append(context.toString());
       sb.append(location.toString());
 
+      if (hint.length() > 0)
+      {
+         sb.append("(hint: ");
+         sb.append(get_hint());
+         sb.append(")");
+      }
+
       return sb.toString();
    }
 
    @Override
    public Origin clone ()
    {
-      return new Origin(context.clone(), location.clone());
+      return new Origin(context.clone(), location.clone(), hint);
    }
 }
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedMergeComputationCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedMergeComputationCompiler.java
index a327d68..3106a29 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedMergeComputationCompiler.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedMergeComputationCompiler.java
@@ -32,104 +32,28 @@ extends GenericComputationCompiler
       super(compiler);
    }
 
-   protected void compile_with_defaults (final IndexedMergeComputation source)
+   protected void compile_without_defaults
+   (
+      final IndexedMergeComputation source
+   )
    throws Throwable
    {
-      final List<Computation> params;
-      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
-      final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
-      final Register result;
-
-      result = reserve(TypeCompiler.compile(compiler, source.get_type()));
-
-      result_as_address = result.get_address();
-      result_as_computation = result.get_value();
-
-      params = new ArrayList<Computation>();
-
-      for
-      (
-         final tonkadur.fate.v1.lang.meta.Computation p:
-            source.get_extra_parameters()
-      )
-      {
-         final ComputationCompiler param_cc;
-
-         param_cc = new ComputationCompiler(compiler);
-
-         p.get_visited_by(param_cc);
-
-         // Let's not re-compute the parameters on every iteration.
-         param_cc.generate_address();
-
-         assimilate(param_cc);
-
-         params.add(param_cc.get_computation());
-      }
-
-      lambda_cc = new ComputationCompiler(compiler);
-
-      source.get_lambda_function().get_visited_by(lambda_cc);
-
-      assimilate(lambda_cc);
-
-      default_a_cc = new ComputationCompiler(compiler);
-
-      source.get_default_a().get_visited_by(default_a_cc);
-
-      default_a_cc.generate_address();
-
-      assimilate(default_a_cc);
-
-      default_b_cc = new ComputationCompiler(compiler);
-
-      source.get_default_b().get_visited_by(default_b_cc);
-
-      default_b_cc.generate_address();
-
-      assimilate(default_b_cc);
-
-      in_collection_a_cc = new ComputationCompiler(compiler);
-
-      source.get_collection_in_a().get_visited_by(in_collection_a_cc);
-
-      assimilate(in_collection_a_cc);
-
-      in_collection_b_cc = new ComputationCompiler(compiler);
-
-      source.get_collection_in_b().get_visited_by(in_collection_b_cc);
-
-      assimilate(in_collection_b_cc);
-
-      init_instructions.add
-      (
-         tonkadur.wyrd.v1.compiler.util.IndexedMergeLambda.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            lambda_cc.get_computation(),
-            default_a_cc.get_computation(),
-            in_collection_a_cc.get_address(),
-            default_b_cc.get_computation(),
-            in_collection_b_cc.get_address(),
-            result_as_address,
-            source.to_set(),
-            params
-         )
-      );
    }
 
-   protected void compile_without_defaults
+   public void compile
    (
-      final IndexedMergeComputation source
+      final tonkadur.fate.v1.lang.computation.GenericComputation computation
    )
    throws Throwable
    {
+      final IndexedMergeComputation source;
       final List<Computation> params;
       final ComputationCompiler lambda_cc;
       final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
       final Register result;
 
+      source = (IndexedMergeComputation) computation;
+
       result = reserve(TypeCompiler.compile(compiler, source.get_type()));
 
       result_as_address = result.get_address();
@@ -190,24 +114,4 @@ extends GenericComputationCompiler
          )
       );
    }
-
-   public void compile
-   (
-      final tonkadur.fate.v1.lang.computation.GenericComputation computation
-   )
-   throws Throwable
-   {
-      final IndexedMergeComputation source;
-
-      source = (IndexedMergeComputation) computation;
-
-      if (source.get_default_a() == null)
-      {
-         compile_without_defaults(source);
-      }
-      else
-      {
-         compile_with_defaults(source);
-      }
-   }
 }
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedSafeMergeComputationCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedSafeMergeComputationCompiler.java
new file mode 100644
index 0000000..97aabdd
--- /dev/null
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/IndexedSafeMergeComputationCompiler.java
@@ -0,0 +1,128 @@
+package tonkadur.wyrd.v1.compiler.fate.v1.computation.generic;
+
+import java.util.List;
+import java.util.ArrayList;
+
+import tonkadur.fate.v1.lang.computation.generic.IndexedSafeMergeComputation;
+
+import tonkadur.wyrd.v1.lang.Register;
+
+import tonkadur.wyrd.v1.lang.instruction.SetValue;
+
+import tonkadur.wyrd.v1.lang.meta.Computation;
+
+import tonkadur.wyrd.v1.lang.type.Type;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.Compiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.TypeCompiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.ComputationCompiler;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.computation.GenericComputationCompiler;
+
+public class IndexedSafeMergeComputationCompiler
+extends GenericComputationCompiler
+{
+   public static Class get_target_class ()
+   {
+      return IndexedSafeMergeComputation.class;
+   }
+
+   public IndexedSafeMergeComputationCompiler (final Compiler compiler)
+   {
+      super(compiler);
+   }
+
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.computation.GenericComputation computation
+   )
+   throws Throwable
+   {
+      final IndexedSafeMergeComputation source;
+      final List<Computation> params;
+      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
+      final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
+      final Register result;
+
+      source = (IndexedSafeMergeComputation) computation;
+
+      result = reserve(TypeCompiler.compile(compiler, source.get_type()));
+
+      result_as_address = result.get_address();
+      result_as_computation = result.get_value();
+
+      params = new ArrayList<Computation>();
+
+      for
+      (
+         final tonkadur.fate.v1.lang.meta.Computation p:
+            source.get_extra_parameters()
+      )
+      {
+         final ComputationCompiler param_cc;
+
+         param_cc = new ComputationCompiler(compiler);
+
+         p.get_visited_by(param_cc);
+
+         // Let's not re-compute the parameters on every iteration.
+         param_cc.generate_address();
+
+         assimilate(param_cc);
+
+         params.add(param_cc.get_computation());
+      }
+
+      lambda_cc = new ComputationCompiler(compiler);
+
+      source.get_lambda_function().get_visited_by(lambda_cc);
+
+      assimilate(lambda_cc);
+
+      default_a_cc = new ComputationCompiler(compiler);
+
+      source.get_default_a().get_visited_by(default_a_cc);
+
+      default_a_cc.generate_address();
+
+      assimilate(default_a_cc);
+
+      default_b_cc = new ComputationCompiler(compiler);
+
+      source.get_default_b().get_visited_by(default_b_cc);
+
+      default_b_cc.generate_address();
+
+      assimilate(default_b_cc);
+
+      in_collection_a_cc = new ComputationCompiler(compiler);
+
+      source.get_collection_in_a().get_visited_by(in_collection_a_cc);
+
+      assimilate(in_collection_a_cc);
+
+      in_collection_b_cc = new ComputationCompiler(compiler);
+
+      source.get_collection_in_b().get_visited_by(in_collection_b_cc);
+
+      assimilate(in_collection_b_cc);
+
+      init_instructions.add
+      (
+         tonkadur.wyrd.v1.compiler.util.IndexedMergeLambda.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            lambda_cc.get_computation(),
+            default_a_cc.get_computation(),
+            in_collection_a_cc.get_address(),
+            default_b_cc.get_computation(),
+            in_collection_b_cc.get_address(),
+            result_as_address,
+            source.to_set(),
+            params
+         )
+      );
+
+   }
+}
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/MergeComputationCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/MergeComputationCompiler.java
index d0cde2f..116ce1e 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/MergeComputationCompiler.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/MergeComputationCompiler.java
@@ -30,101 +30,20 @@ extends GenericComputationCompiler
       super(compiler);
    }
 
-   protected void compile_with_defaults (final MergeComputation source)
-   throws Throwable
-   {
-      final List<Computation> params;
-      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
-      final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
-      final Register result;
-
-      result = reserve(TypeCompiler.compile(compiler, source.get_type()));
-
-      result_as_address = result.get_address();
-      result_as_computation = result.get_value();
-
-      params = new ArrayList<Computation>();
-
-      for
-      (
-         final tonkadur.fate.v1.lang.meta.Computation p:
-            source.get_extra_parameters()
-      )
-      {
-         final ComputationCompiler param_cc;
-
-         param_cc = new ComputationCompiler(compiler);
-
-         p.get_visited_by(param_cc);
-
-         // Let's not re-compute the parameters on every iteration.
-         param_cc.generate_address();
-
-         assimilate(param_cc);
-
-         params.add(param_cc.get_computation());
-      }
-
-      lambda_cc = new ComputationCompiler(compiler);
-
-      source.get_lambda_function().get_visited_by(lambda_cc);
-
-      assimilate(lambda_cc);
-
-      default_a_cc = new ComputationCompiler(compiler);
-
-      source.get_default_a().get_visited_by(default_a_cc);
-
-      default_a_cc.generate_address();
-
-      assimilate(default_a_cc);
-
-      default_b_cc = new ComputationCompiler(compiler);
-
-      source.get_default_b().get_visited_by(default_b_cc);
-
-      default_b_cc.generate_address();
-
-      assimilate(default_b_cc);
-
-      in_collection_a_cc = new ComputationCompiler(compiler);
-
-      source.get_collection_in_a().get_visited_by(in_collection_a_cc);
-
-      assimilate(in_collection_a_cc);
-
-      in_collection_b_cc = new ComputationCompiler(compiler);
-
-      source.get_collection_in_b().get_visited_by(in_collection_b_cc);
-
-      assimilate(in_collection_b_cc);
-
-      init_instructions.add
-      (
-         tonkadur.wyrd.v1.compiler.util.MergeLambda.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            lambda_cc.get_computation(),
-            default_a_cc.get_computation(),
-            in_collection_a_cc.get_address(),
-            default_b_cc.get_computation(),
-            in_collection_b_cc.get_address(),
-            result_as_address,
-            source.to_set(),
-            params
-         )
-      );
-   }
-
-   protected void compile_without_defaults (final MergeComputation source)
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.computation.GenericComputation computation
+   )
    throws Throwable
    {
+      final MergeComputation source;
       final List<Computation> params;
       final ComputationCompiler lambda_cc;
       final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
       final Register result;
 
+      source = (MergeComputation) computation;
+
       result = reserve(TypeCompiler.compile(compiler, source.get_type()));
 
       result_as_address = result.get_address();
@@ -185,24 +104,4 @@ extends GenericComputationCompiler
          )
       );
    }
-
-   public void compile
-   (
-      final tonkadur.fate.v1.lang.computation.GenericComputation computation
-   )
-   throws Throwable
-   {
-      final MergeComputation source;
-
-      source = (MergeComputation) computation;
-
-      if (source.get_default_a() == null)
-      {
-         compile_without_defaults(source);
-      }
-      else
-      {
-         compile_with_defaults(source);
-      }
-   }
 }
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/SafeMergeComputation.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/SafeMergeComputation.java
new file mode 100644
index 0000000..17673da
--- /dev/null
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/computation/generic/SafeMergeComputation.java
@@ -0,0 +1,126 @@
+package tonkadur.wyrd.v1.compiler.fate.v1.computation.generic;
+
+import java.util.List;
+import java.util.ArrayList;
+
+import tonkadur.fate.v1.lang.computation.generic.SafeMergeComputation;
+
+import tonkadur.wyrd.v1.lang.Register;
+
+import tonkadur.wyrd.v1.lang.meta.Computation;
+
+import tonkadur.wyrd.v1.lang.type.Type;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.Compiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.TypeCompiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.ComputationCompiler;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.computation.GenericComputationCompiler;
+
+public class SafeMergeComputationCompiler
+extends GenericComputationCompiler
+{
+   public static Class get_target_class ()
+   {
+      return SafeMergeComputation.class;
+   }
+
+   public SafeMergeComputationCompiler (final Compiler compiler)
+   {
+      super(compiler);
+   }
+
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.computation.GenericComputation computation
+   )
+   throws Throwable
+   {
+      final SafeMergeComputation source;
+      final List<Computation> params;
+      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
+      final ComputationCompiler in_collection_a_cc, in_collection_b_cc;
+      final Register result;
+
+      source = (SafeMergeComputation) computation;
+
+      result = reserve(TypeCompiler.compile(compiler, source.get_type()));
+
+      result_as_address = result.get_address();
+      result_as_computation = result.get_value();
+
+      params = new ArrayList<Computation>();
+
+      for
+      (
+         final tonkadur.fate.v1.lang.meta.Computation p:
+            source.get_extra_parameters()
+      )
+      {
+         final ComputationCompiler param_cc;
+
+         param_cc = new ComputationCompiler(compiler);
+
+         p.get_visited_by(param_cc);
+
+         // Let's not re-compute the parameters on every iteration.
+         param_cc.generate_address();
+
+         assimilate(param_cc);
+
+         params.add(param_cc.get_computation());
+      }
+
+      lambda_cc = new ComputationCompiler(compiler);
+
+      source.get_lambda_function().get_visited_by(lambda_cc);
+
+      assimilate(lambda_cc);
+
+      default_a_cc = new ComputationCompiler(compiler);
+
+      source.get_default_a().get_visited_by(default_a_cc);
+
+      default_a_cc.generate_address();
+
+      assimilate(default_a_cc);
+
+      default_b_cc = new ComputationCompiler(compiler);
+
+      source.get_default_b().get_visited_by(default_b_cc);
+
+      default_b_cc.generate_address();
+
+      assimilate(default_b_cc);
+
+      in_collection_a_cc = new ComputationCompiler(compiler);
+
+      source.get_collection_in_a().get_visited_by(in_collection_a_cc);
+
+      assimilate(in_collection_a_cc);
+
+      in_collection_b_cc = new ComputationCompiler(compiler);
+
+      source.get_collection_in_b().get_visited_by(in_collection_b_cc);
+
+      assimilate(in_collection_b_cc);
+
+      init_instructions.add
+      (
+         tonkadur.wyrd.v1.compiler.util.MergeLambda.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            lambda_cc.get_computation(),
+            default_a_cc.get_computation(),
+            in_collection_a_cc.get_address(),
+            default_b_cc.get_computation(),
+            in_collection_b_cc.get_address(),
+            result_as_address,
+            source.to_set(),
+            params
+         )
+      );
+
+   }
+}
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedMergeCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedMergeCompiler.java
index 0f94485..8d4d4a5 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedMergeCompiler.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedMergeCompiler.java
@@ -28,161 +28,21 @@ public class IndexedMergeCompiler extends GenericInstructionCompiler
       super(compiler);
    }
 
-   private void compile_indexed_merge_with_defaults (final IndexedMerge source)
-   throws Throwable
-   {
-      final Register holder;
-      final ComputationCompiler lambda_cc;
-      final ComputationCompiler main_default_cc, secondary_default_cc;
-      final List<Computation> params;
-      final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler main_collection_cc, secondary_collection_cc;
-
-      params = new ArrayList<Computation>();
-      param_cc_list = new ArrayList<ComputationCompiler>();
-
-      lambda_cc = new ComputationCompiler(compiler);
-      main_default_cc = new ComputationCompiler(compiler);
-      secondary_default_cc = new ComputationCompiler(compiler);
-
-      source.get_lambda_function().get_visited_by(lambda_cc);
-
-      if (lambda_cc.has_init())
-      {
-         result.add(lambda_cc.get_init());
-      }
-
-      main_collection_cc = new ComputationCompiler(compiler);
-
-      source.get_main_collection().get_visited_by(main_collection_cc);
-
-      if (main_collection_cc.has_init())
-      {
-         result.add(main_collection_cc.get_init());
-      }
-
-      source.get_main_default().get_visited_by(main_default_cc);
-
-      main_default_cc.generate_address();
-
-      if (main_default_cc.has_init())
-      {
-         result.add(main_default_cc.get_init());
-      }
-
-      source.get_secondary_default().get_visited_by(secondary_default_cc);
-
-      secondary_default_cc.generate_address();
-
-      if (secondary_default_cc.has_init())
-      {
-         result.add(secondary_default_cc.get_init());
-      }
-
-      holder =
-         compiler.registers().reserve
-         (
-            main_collection_cc.get_computation().get_type(),
-            result
-         );
-
-      result.add
-      (
-         new SetValue
-         (
-            holder.get_address(),
-            main_collection_cc.get_computation()
-         )
-      );
-
-      result.add
-      (
-         tonkadur.wyrd.v1.compiler.util.Clear.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            main_collection_cc.get_address()
-         )
-      );
-
-      secondary_collection_cc = new ComputationCompiler(compiler);
-
-      source.get_secondary_collection().get_visited_by(secondary_collection_cc);
-
-      if (secondary_collection_cc.has_init())
-      {
-         result.add(secondary_collection_cc.get_init());
-      }
-
-      for
-      (
-         final tonkadur.fate.v1.lang.meta.Computation p:
-            source.get_extra_parameters()
-      )
-      {
-         final ComputationCompiler param_cc;
-
-         param_cc = new ComputationCompiler(compiler);
-
-         p.get_visited_by(param_cc);
-
-         // Let's not re-compute the parameters on every iteration.
-         param_cc.generate_address();
-
-         if (param_cc.has_init())
-         {
-            result.add(param_cc.get_init());
-         }
-
-         param_cc_list.add(param_cc);
-
-         params.add(param_cc.get_computation());
-      }
-
-      result.add
-      (
-         tonkadur.wyrd.v1.compiler.util.IndexedMergeLambda.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            lambda_cc.get_computation(),
-            secondary_default_cc.get_computation(),
-            secondary_collection_cc.get_address(),
-            main_default_cc.get_computation(),
-            holder.get_address(),
-            main_collection_cc.get_address(),
-            (
-               (tonkadur.fate.v1.lang.type.CollectionType)
-               source.get_main_collection().get_type()
-            ).is_set(),
-            params
-         )
-      );
-
-      main_collection_cc.release_registers(result);
-      secondary_collection_cc.release_registers(result);
-      main_default_cc.release_registers(result);
-      secondary_default_cc.release_registers(result);
-      compiler.registers().release(holder, result);
-
-      for (final ComputationCompiler cc: param_cc_list)
-      {
-         cc.release_registers(result);
-      }
-   }
-
-   private void compile_indexed_merge_without_defaults
+   public void compile
    (
-      final IndexedMerge source
+      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
    )
    throws Throwable
    {
+      final IndexedMerge source;
       final Register holder;
       final ComputationCompiler lambda_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
       final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
+      source = (IndexedMerge) instruction;
+
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
 
@@ -291,24 +151,4 @@ public class IndexedMergeCompiler extends GenericInstructionCompiler
          cc.release_registers(result);
       }
    }
-
-   public void compile
-   (
-      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
-   )
-   throws Throwable
-   {
-      final IndexedMerge source;
-
-      source = (IndexedMerge) instruction;
-
-      if (source.get_main_default() != null)
-      {
-         compile_indexed_merge_with_defaults(source);
-      }
-      else
-      {
-         compile_indexed_merge_without_defaults(source);
-      }
-   }
 }
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedSafeMergeCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedSafeMergeCompiler.java
new file mode 100644
index 0000000..726ad2e
--- /dev/null
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/IndexedSafeMergeCompiler.java
@@ -0,0 +1,179 @@
+package tonkadur.wyrd.v1.compiler.fate.v1.instruction.generic;
+
+import java.util.List;
+import java.util.ArrayList;
+
+import tonkadur.fate.v1.lang.instruction.generic.IndexedSafeMerge;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.Compiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.ComputationCompiler;
+
+import tonkadur.wyrd.v1.lang.Register;
+
+import tonkadur.wyrd.v1.lang.meta.Computation;
+
+import tonkadur.wyrd.v1.lang.instruction.SetValue;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.instruction.GenericInstructionCompiler;
+
+public class IndexedSafeMergeCompiler extends GenericInstructionCompiler
+{
+   public static Class get_target_class ()
+   {
+      return IndexedSafeMerge.class;
+   }
+
+   public IndexedSafeMergeCompiler (final Compiler compiler)
+   {
+      super(compiler);
+   }
+
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
+   )
+   throws Throwable
+   {
+      final IndexedSafeMerge source;
+      final Register holder;
+      final ComputationCompiler lambda_cc;
+      final ComputationCompiler main_default_cc, secondary_default_cc;
+      final List<Computation> params;
+      final List<ComputationCompiler> param_cc_list;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
+
+      source = (IndexedSafeMerge) instruction;
+
+      params = new ArrayList<Computation>();
+      param_cc_list = new ArrayList<ComputationCompiler>();
+
+      lambda_cc = new ComputationCompiler(compiler);
+      main_default_cc = new ComputationCompiler(compiler);
+      secondary_default_cc = new ComputationCompiler(compiler);
+
+      source.get_lambda_function().get_visited_by(lambda_cc);
+
+      if (lambda_cc.has_init())
+      {
+         result.add(lambda_cc.get_init());
+      }
+
+      main_collection_cc = new ComputationCompiler(compiler);
+
+      source.get_main_collection().get_visited_by(main_collection_cc);
+
+      if (main_collection_cc.has_init())
+      {
+         result.add(main_collection_cc.get_init());
+      }
+
+      source.get_main_default().get_visited_by(main_default_cc);
+
+      main_default_cc.generate_address();
+
+      if (main_default_cc.has_init())
+      {
+         result.add(main_default_cc.get_init());
+      }
+
+      source.get_secondary_default().get_visited_by(secondary_default_cc);
+
+      secondary_default_cc.generate_address();
+
+      if (secondary_default_cc.has_init())
+      {
+         result.add(secondary_default_cc.get_init());
+      }
+
+      holder =
+         compiler.registers().reserve
+         (
+            main_collection_cc.get_computation().get_type(),
+            result
+         );
+
+      result.add
+      (
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
+      );
+
+      result.add
+      (
+         tonkadur.wyrd.v1.compiler.util.Clear.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            main_collection_cc.get_address()
+         )
+      );
+
+      secondary_collection_cc = new ComputationCompiler(compiler);
+
+      source.get_secondary_collection().get_visited_by(secondary_collection_cc);
+
+      if (secondary_collection_cc.has_init())
+      {
+         result.add(secondary_collection_cc.get_init());
+      }
+
+      for
+      (
+         final tonkadur.fate.v1.lang.meta.Computation p:
+            source.get_extra_parameters()
+      )
+      {
+         final ComputationCompiler param_cc;
+
+         param_cc = new ComputationCompiler(compiler);
+
+         p.get_visited_by(param_cc);
+
+         // Let's not re-compute the parameters on every iteration.
+         param_cc.generate_address();
+
+         if (param_cc.has_init())
+         {
+            result.add(param_cc.get_init());
+         }
+
+         param_cc_list.add(param_cc);
+
+         params.add(param_cc.get_computation());
+      }
+
+      result.add
+      (
+         tonkadur.wyrd.v1.compiler.util.IndexedMergeLambda.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            lambda_cc.get_computation(),
+            secondary_default_cc.get_computation(),
+            secondary_collection_cc.get_address(),
+            main_default_cc.get_computation(),
+            holder.get_address(),
+            main_collection_cc.get_address(),
+            (
+               (tonkadur.fate.v1.lang.type.CollectionType)
+               source.get_main_collection().get_type()
+            ).is_set(),
+            params
+         )
+      );
+
+      main_collection_cc.release_registers(result);
+      secondary_collection_cc.release_registers(result);
+      main_default_cc.release_registers(result);
+      secondary_default_cc.release_registers(result);
+      compiler.registers().release(holder, result);
+
+      for (final ComputationCompiler cc: param_cc_list)
+      {
+         cc.release_registers(result);
+      }
+   }
+}
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/MergeCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/MergeCompiler.java
index 21c817e..12f77e9 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/MergeCompiler.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/MergeCompiler.java
@@ -28,157 +28,20 @@ public class MergeCompiler extends GenericInstructionCompiler
       super(compiler);
    }
 
-   private void compile_merge_with_defaults (final Merge source)
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
+   )
    throws Throwable
    {
+      final Merge source;
       final Register holder;
       final ComputationCompiler lambda_cc;
-      final ComputationCompiler main_default_cc, secondary_default_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
       final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
-      params = new ArrayList<Computation>();
-      param_cc_list = new ArrayList<ComputationCompiler>();
-
-      lambda_cc = new ComputationCompiler(compiler);
-      main_default_cc = new ComputationCompiler(compiler);
-      secondary_default_cc = new ComputationCompiler(compiler);
-
-      source.get_lambda_function().get_visited_by(lambda_cc);
-
-      if (lambda_cc.has_init())
-      {
-         result.add(lambda_cc.get_init());
-      }
-
-      main_collection_cc = new ComputationCompiler(compiler);
-
-      source.get_main_collection().get_visited_by(main_collection_cc);
-
-      if (main_collection_cc.has_init())
-      {
-         result.add(main_collection_cc.get_init());
-      }
-
-      source.get_main_default().get_visited_by(main_default_cc);
-
-      main_default_cc.generate_address();
-
-      if (main_default_cc.has_init())
-      {
-         result.add(main_default_cc.get_init());
-      }
-
-      source.get_secondary_default().get_visited_by(secondary_default_cc);
-
-      secondary_default_cc.generate_address();
-
-      if (secondary_default_cc.has_init())
-      {
-         result.add(secondary_default_cc.get_init());
-      }
-
-      holder =
-         compiler.registers().reserve
-         (
-            main_collection_cc.get_computation().get_type(),
-            result
-         );
-
-      result.add
-      (
-         new SetValue
-         (
-            holder.get_address(),
-            main_collection_cc.get_computation()
-         )
-      );
-
-      result.add
-      (
-         tonkadur.wyrd.v1.compiler.util.Clear.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            main_collection_cc.get_address()
-         )
-      );
-
-      secondary_collection_cc = new ComputationCompiler(compiler);
-
-      source.get_secondary_collection().get_visited_by(secondary_collection_cc);
-
-      if (secondary_collection_cc.has_init())
-      {
-         result.add(secondary_collection_cc.get_init());
-      }
-
-      for
-      (
-         final tonkadur.fate.v1.lang.meta.Computation p:
-            source.get_extra_parameters()
-      )
-      {
-         final ComputationCompiler param_cc;
-
-         param_cc = new ComputationCompiler(compiler);
-
-         p.get_visited_by(param_cc);
-
-         // Let's not re-compute the parameters on every iteration.
-         param_cc.generate_address();
-
-         if (param_cc.has_init())
-         {
-            result.add(param_cc.get_init());
-         }
-
-         param_cc_list.add(param_cc);
-
-         params.add(param_cc.get_computation());
-      }
-
-      result.add
-      (
-         tonkadur.wyrd.v1.compiler.util.MergeLambda.generate
-         (
-            compiler.registers(),
-            compiler.assembler(),
-            lambda_cc.get_computation(),
-            secondary_default_cc.get_computation(),
-            secondary_collection_cc.get_address(),
-            main_default_cc.get_computation(),
-            holder.get_address(),
-            main_collection_cc.get_address(),
-            (
-               (tonkadur.fate.v1.lang.type.CollectionType)
-               source.get_main_collection().get_type()
-            ).is_set(),
-            params
-         )
-      );
-
-      main_collection_cc.release_registers(result);
-      secondary_collection_cc.release_registers(result);
-      main_default_cc.release_registers(result);
-      secondary_default_cc.release_registers(result);
-      compiler.registers().release(holder, result);
-
-      for (final ComputationCompiler cc: param_cc_list)
-      {
-         cc.release_registers(result);
-      }
-   }
-
-   private void compile_merge_without_defaults (final Merge source)
-   throws Throwable
-   {
-      final Register holder;
-      final ComputationCompiler lambda_cc;
-      final List<Computation> params;
-      final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler main_collection_cc, secondary_collection_cc;
+      source = (Merge) instruction;
 
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
@@ -288,24 +151,4 @@ public class MergeCompiler extends GenericInstructionCompiler
          cc.release_registers(result);
       }
    }
-
-   public void compile
-   (
-      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
-   )
-   throws Throwable
-   {
-      final Merge source;
-
-      source = (Merge) instruction;
-
-      if (source.get_main_default() != null)
-      {
-         compile_merge_with_defaults(source);
-      }
-      else
-      {
-         compile_merge_without_defaults(source);
-      }
-   }
 }
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/SafeMergeCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/SafeMergeCompiler.java
new file mode 100644
index 0000000..128569d
--- /dev/null
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/instruction/generic/SafeMergeCompiler.java
@@ -0,0 +1,180 @@
+package tonkadur.wyrd.v1.compiler.fate.v1.instruction.generic;
+
+import java.util.List;
+import java.util.ArrayList;
+
+import tonkadur.fate.v1.lang.instruction.generic.SafeMerge;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.Compiler;
+import tonkadur.wyrd.v1.compiler.fate.v1.ComputationCompiler;
+
+import tonkadur.wyrd.v1.lang.Register;
+
+import tonkadur.wyrd.v1.lang.meta.Computation;
+
+import tonkadur.wyrd.v1.lang.instruction.SetValue;
+
+import tonkadur.wyrd.v1.compiler.fate.v1.instruction.GenericInstructionCompiler;
+
+public class SafeMergeCompiler extends GenericInstructionCompiler
+{
+   public static Class get_target_class ()
+   {
+      return SafeMerge.class;
+   }
+
+   public SafeMergeCompiler (final Compiler compiler)
+   {
+      super(compiler);
+   }
+
+   public void compile
+   (
+      final tonkadur.fate.v1.lang.instruction.GenericInstruction instruction
+   )
+   throws Throwable
+   {
+      final SafeMerge source;
+      final Register holder;
+      final ComputationCompiler lambda_cc;
+      final ComputationCompiler main_default_cc, secondary_default_cc;
+      final List<Computation> params;
+      final List<ComputationCompiler> param_cc_list;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
+
+      source = (SafeMerge) instruction;
+
+      params = new ArrayList<Computation>();
+      param_cc_list = new ArrayList<ComputationCompiler>();
+
+      lambda_cc = new ComputationCompiler(compiler);
+      main_default_cc = new ComputationCompiler(compiler);
+      secondary_default_cc = new ComputationCompiler(compiler);
+
+      source.get_lambda_function().get_visited_by(lambda_cc);
+
+      if (lambda_cc.has_init())
+      {
+         result.add(lambda_cc.get_init());
+      }
+
+      main_collection_cc = new ComputationCompiler(compiler);
+
+      source.get_main_collection().get_visited_by(main_collection_cc);
+
+      if (main_collection_cc.has_init())
+      {
+         result.add(main_collection_cc.get_init());
+      }
+
+      source.get_main_default().get_visited_by(main_default_cc);
+
+      main_default_cc.generate_address();
+
+      if (main_default_cc.has_init())
+      {
+         result.add(main_default_cc.get_init());
+      }
+
+      source.get_secondary_default().get_visited_by(secondary_default_cc);
+
+      secondary_default_cc.generate_address();
+
+      if (secondary_default_cc.has_init())
+      {
+         result.add(secondary_default_cc.get_init());
+      }
+
+      holder =
+         compiler.registers().reserve
+         (
+            main_collection_cc.get_computation().get_type(),
+            result
+         );
+
+      result.add
+      (
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
+      );
+
+      result.add
+      (
+         tonkadur.wyrd.v1.compiler.util.Clear.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            main_collection_cc.get_address()
+         )
+      );
+
+      secondary_collection_cc = new ComputationCompiler(compiler);
+
+      source.get_secondary_collection().get_visited_by(secondary_collection_cc);
+
+      if (secondary_collection_cc.has_init())
+      {
+         result.add(secondary_collection_cc.get_init());
+      }
+
+      for
+      (
+         final tonkadur.fate.v1.lang.meta.Computation p:
+            source.get_extra_parameters()
+      )
+      {
+         final ComputationCompiler param_cc;
+
+         param_cc = new ComputationCompiler(compiler);
+
+         p.get_visited_by(param_cc);
+
+         // Let's not re-compute the parameters on every iteration.
+         param_cc.generate_address();
+
+         if (param_cc.has_init())
+         {
+            result.add(param_cc.get_init());
+         }
+
+         param_cc_list.add(param_cc);
+
+         params.add(param_cc.get_computation());
+      }
+
+      result.add
+      (
+         tonkadur.wyrd.v1.compiler.util.MergeLambda.generate
+         (
+            compiler.registers(),
+            compiler.assembler(),
+            lambda_cc.get_computation(),
+            secondary_default_cc.get_computation(),
+            secondary_collection_cc.get_address(),
+            main_default_cc.get_computation(),
+            holder.get_address(),
+            main_collection_cc.get_address(),
+            (
+               (tonkadur.fate.v1.lang.type.CollectionType)
+               source.get_main_collection().get_type()
+            ).is_set(),
+            params
+         )
+      );
+
+      main_collection_cc.release_registers(result);
+      secondary_collection_cc.release_registers(result);
+      main_default_cc.release_registers(result);
+      secondary_default_cc.release_registers(result);
+      compiler.registers().release(holder, result);
+
+      for (final ComputationCompiler cc: param_cc_list)
+      {
+         cc.release_registers(result);
+      }
+
+   }
+}