Parenthesis, merge stuff, main param goes last.

6 files changed, 271 insertions, 189 deletions

diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/IndexedMerge.java b/src/core/src/tonkadur/fate/v1/lang/instruction/IndexedMerge.java
index 96cfefc..060438c 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/IndexedMerge.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/IndexedMerge.java
@@ -35,10 +35,10 @@ public class IndexedMerge extends Instruction
    (
       final Origin origin,
       final Computation lambda_function,
-      final Reference collection,
-      final Computation default_a,
       final Computation collection_in_b,
       final Computation default_b,
+      final Reference collection,
+      final Computation default_a,
       final List<Computation> extra_params
    )
    {
@@ -60,10 +60,10 @@ public class IndexedMerge extends Instruction
    (
       final Origin origin,
       final Computation lambda_function,
-      final Reference collection,
-      final Computation default_a,
       final Computation collection_in_b,
       final Computation default_b,
+      final Reference collection,
+      final Computation default_a,
       final List<Computation> extra_params
    )
    throws Throwable
@@ -123,10 +123,10 @@ public class IndexedMerge extends Instruction
          (
             origin,
             lambda_function,
-            collection,
-            default_a,
             collection_in_b,
             default_b,
+            collection,
+            default_a,
             extra_params
          );
    }
@@ -144,22 +144,22 @@ public class IndexedMerge extends Instruction
       return lambda_function;
    }
 
-   public Computation get_default_a ()
+   public Computation get_main_default ()
    {
       return default_a;
    }
 
-   public Computation get_collection_in_b ()
+   public Computation get_secondary_collection ()
    {
       return collection_in_b;
    }
 
-   public Computation get_default_b ()
+   public Computation get_secondary_default ()
    {
       return default_b;
    }
 
-   public Reference get_collection ()
+   public Reference get_main_collection ()
    {
       return collection;
    }
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/Merge.java b/src/core/src/tonkadur/fate/v1/lang/instruction/Merge.java
index f2396a9..9a40f2f 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/Merge.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/Merge.java
@@ -35,10 +35,10 @@ public class Merge extends Instruction
    (
       final Origin origin,
       final Computation lambda_function,
-      final Reference collection,
-      final Computation default_a,
       final Computation collection_in_b,
       final Computation default_b,
+      final Reference collection,
+      final Computation default_a,
       final List<Computation> extra_params
    )
    {
@@ -60,10 +60,10 @@ public class Merge extends Instruction
    (
       final Origin origin,
       final Computation lambda_function,
-      final Reference collection,
-      final Computation default_a,
       final Computation collection_in_b,
       final Computation default_b,
+      final Reference collection,
+      final Computation default_a,
       final List<Computation> extra_params
    )
    throws Throwable
@@ -117,10 +117,10 @@ public class Merge extends Instruction
          (
             origin,
             lambda_function,
-            collection,
-            default_a,
             collection_in_b,
             default_b,
+            collection,
+            default_a,
             extra_params
          );
    }
@@ -138,22 +138,22 @@ public class Merge extends Instruction
       return lambda_function;
    }
 
-   public Computation get_default_a ()
+   public Computation get_main_default ()
    {
       return default_a;
    }
 
-   public Computation get_collection_in_b ()
+   public Computation get_secondary_collection ()
    {
       return collection_in_b;
    }
 
-   public Computation get_default_b ()
+   public Computation get_secondary_default ()
    {
       return default_b;
    }
 
-   public Reference get_collection ()
+   public Reference get_main_collection ()
    {
       return collection;
    }
diff --git a/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4 b/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
index 10bb692..b7b64dd 100644
--- a/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
+++ b/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
@@ -8,6 +8,7 @@ lexer grammar FateLexer;
 fragment SEP: [ \t\r\n]+;
 fragment US: '_'?;
 
+
 WS: SEP;
 
 L_PAREN: '(';
@@ -162,6 +163,9 @@ VISIT_KW: L_PAREN ('call'|'visit')(US(('seq'('uence'?))|('proc'('edure'?))))? SE
 CONTINUE_AS_KW: L_PAREN (('continue'US('as'|'to'|'with'))|('jump'(US'to')?)|('go'US'to')|'exec')(US(('seq'('uence'?))|('proc'('edure'?))))? SEP+;
 WHILE_KW: L_PAREN 'while' SEP+;
 
-WORD: (~([ \t\r\n()])|'\\)'|'\\(')+;
+WORD: ((~([ \t\r\n()]))|'(lp)'|'(rp)')+
+   {
+      setText(getText().replaceAll("\\(lp\\)", "(").replaceAll("\\(rp\\)", ")"));
+   };
 
 COMMENT: WS* ';' .*? '\n' -> channel(HIDDEN);
diff --git a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4 b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
index d16dfb2..16a9472 100644
--- a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
+++ b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
@@ -977,8 +977,8 @@ returns [Instruction result]
 
    | IMP_MERGE_KW
          fun=non_text_value WS+
-         value_reference WS+
-         inv1=non_text_value WS*
+         inv1=non_text_value WS+
+         value_reference WS*
       R_PAREN
    {
       $result =
@@ -990,18 +990,18 @@ returns [Instruction result]
                ($IMP_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            null,
             ($inv1.result),
             null,
+            ($value_reference.result),
+            null,
             new ArrayList()
          );
    }
 
    | IMP_MERGE_KW
          fun=non_text_value WS+
-         value_reference WS+
          inv1=non_text_value WS+
+         value_reference WS+
          value_list WS*
       R_PAREN
    {
@@ -1014,18 +1014,18 @@ returns [Instruction result]
                ($IMP_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            null,
             ($inv1.result),
             null,
+            ($value_reference.result),
+            null,
             ($value_list.result)
          );
    }
 
    | IMP_INDEXED_MERGE_KW
          fun=non_text_value WS+
-         value_reference WS+
-         inv1=non_text_value WS*
+         inv1=non_text_value WS+
+         value_reference WS*
       R_PAREN
    {
       $result =
@@ -1037,18 +1037,18 @@ returns [Instruction result]
                ($IMP_INDEXED_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            null,
             ($inv1.result),
             null,
+            ($value_reference.result),
+            null,
             new ArrayList()
          );
    }
 
    | IMP_INDEXED_MERGE_KW
          fun=non_text_value WS+
-         value_reference WS+
          inv1=non_text_value WS+
+         value_reference WS+
          value_list WS*
       R_PAREN
    {
@@ -1061,20 +1061,20 @@ returns [Instruction result]
                ($IMP_INDEXED_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            null,
             ($inv1.result),
             null,
+            ($value_reference.result),
+            null,
             ($value_list.result)
          );
    }
 
    | SAFE_IMP_MERGE_KW
       fun=non_text_value WS+
-      def0=value WS+
-      value_reference WS+
       def1=value WS+
-      inv1=non_text_value WS*
+      inv1=non_text_value WS+
+      def0=value WS+
+      value_reference WS*
       R_PAREN
    {
       $result =
@@ -1086,20 +1086,20 @@ returns [Instruction result]
                ($SAFE_IMP_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            ($def0.result),
             ($inv1.result),
             ($def1.result),
+            ($value_reference.result),
+            ($def0.result),
             new ArrayList()
          );
    }
 
    | SAFE_IMP_MERGE_KW
       fun=non_text_value WS+
-      def0=value WS+
-      value_reference WS+
       def1=value WS+
       inv1=non_text_value WS+
+      def0=value WS+
+      value_reference WS+
       value_list WS*
       R_PAREN
    {
@@ -1112,20 +1112,20 @@ returns [Instruction result]
                ($SAFE_IMP_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            ($def0.result),
             ($inv1.result),
             ($def1.result),
+            ($value_reference.result),
+            ($def0.result),
             ($value_list.result)
          );
    }
 
    | SAFE_IMP_INDEXED_MERGE_KW
       fun=non_text_value WS+
-      def0=value WS+
-      value_reference WS+
       def1=value WS+
-      inv1=non_text_value WS*
+      inv1=non_text_value WS+
+      def0=value WS+
+      value_reference WS*
       R_PAREN
    {
       $result =
@@ -1137,20 +1137,20 @@ returns [Instruction result]
                ($SAFE_IMP_INDEXED_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            ($def0.result),
             ($inv1.result),
             ($def1.result),
+            ($value_reference.result),
+            ($def0.result),
             new ArrayList()
          );
    }
 
    | SAFE_IMP_INDEXED_MERGE_KW
       fun=non_text_value WS+
-      def0=value WS+
-      value_reference WS+
       def1=value WS+
       inv1=non_text_value WS+
+      def0=value WS+
+      value_reference WS+
       value_list WS*
       R_PAREN
    {
@@ -1163,10 +1163,10 @@ returns [Instruction result]
                ($SAFE_IMP_INDEXED_MERGE_KW.getCharPositionInLine())
             ),
             ($fun.result),
-            ($value_reference.result),
-            ($def0.result),
             ($inv1.result),
             ($def1.result),
+            ($value_reference.result),
+            ($def0.result),
             ($value_list.result)
          );
    }
@@ -3743,7 +3743,7 @@ returns [Computation result]
          );
    }
 
-   | ACCESS_KW collection=non_text_value WS+ index=non_text_value WS* R_PAREN
+   | ACCESS_KW index=non_text_value WS+ collection=non_text_value WS* R_PAREN
    {
       $result =
          Access.build
@@ -3758,7 +3758,7 @@ returns [Computation result]
          );
    }
 
-   | ACCESS_POINTER_KW value_reference WS+ non_text_value WS* R_PAREN
+   | ACCESS_POINTER_KW non_text_value WS+ value_reference WS* R_PAREN
    {
       $result =
          AccessPointer.build
@@ -3773,7 +3773,7 @@ returns [Computation result]
          );
    }
 
-   | FIELD_ACCESS_KW non_text_value WS+ WORD WS* R_PAREN
+   | FIELD_ACCESS_KW WORD WS+ non_text_value WS* R_PAREN
    {
       $result =
          FieldAccess.build
@@ -5115,7 +5115,7 @@ returns [Reference result]
          );
    }
 
-   | FIELD_KW value_reference WS+ WORD WS* R_PAREN
+   | FIELD_KW WORD WS+ value_reference WS* R_PAREN
    {
       $result =
          FieldReference.build
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/InstructionCompiler.java b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/InstructionCompiler.java
index 19baae7..5986682 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/InstructionCompiler.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/fate/v1/InstructionCompiler.java
@@ -749,17 +749,18 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
    throws Throwable
    {
       final Register holder;
-      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
+      final ComputationCompiler lambda_cc;
+      final ComputationCompiler main_default_cc, secondary_default_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler collection_cc, in_collection_b_cc;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
 
       lambda_cc = new ComputationCompiler(compiler);
-      default_a_cc = new ComputationCompiler(compiler);
-      default_b_cc = new ComputationCompiler(compiler);
+      main_default_cc = new ComputationCompiler(compiler);
+      secondary_default_cc = new ComputationCompiler(compiler);
 
       n.get_lambda_function().get_visited_by(lambda_cc);
 
@@ -768,43 +769,47 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          result.add(lambda_cc.get_init());
       }
 
-      collection_cc = new ComputationCompiler(compiler);
+      main_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection().get_visited_by(collection_cc);
+      n.get_main_collection().get_visited_by(main_collection_cc);
 
-      if (collection_cc.has_init())
+      if (main_collection_cc.has_init())
       {
-         result.add(collection_cc.get_init());
+         result.add(main_collection_cc.get_init());
       }
 
-      n.get_default_a().get_visited_by(default_a_cc);
+      n.get_main_default().get_visited_by(main_default_cc);
 
-      default_a_cc.generate_address();
+      main_default_cc.generate_address();
 
-      if (default_a_cc.has_init())
+      if (main_default_cc.has_init())
       {
-         result.add(default_a_cc.get_init());
+         result.add(main_default_cc.get_init());
       }
 
-      n.get_default_b().get_visited_by(default_b_cc);
+      n.get_secondary_default().get_visited_by(secondary_default_cc);
 
-      default_b_cc.generate_address();
+      secondary_default_cc.generate_address();
 
-      if (default_b_cc.has_init())
+      if (secondary_default_cc.has_init())
       {
-         result.add(default_b_cc.get_init());
+         result.add(secondary_default_cc.get_init());
       }
 
       holder =
          compiler.registers().reserve
          (
-            collection_cc.get_computation().get_type(),
+            main_collection_cc.get_computation().get_type(),
             result
          );
 
       result.add
       (
-         new SetValue(holder.get_address(), collection_cc.get_computation())
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
       );
 
       result.add
@@ -813,17 +818,17 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          (
             compiler.registers(),
             compiler.assembler(),
-            collection_cc.get_address()
+            main_collection_cc.get_address()
          )
       );
 
-      in_collection_b_cc = new ComputationCompiler(compiler);
+      secondary_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection_in_b().get_visited_by(in_collection_b_cc);
+      n.get_secondary_collection().get_visited_by(secondary_collection_cc);
 
-      if (in_collection_b_cc.has_init())
+      if (secondary_collection_cc.has_init())
       {
-         result.add(in_collection_b_cc.get_init());
+         result.add(secondary_collection_cc.get_init());
       }
 
       for
@@ -858,23 +863,23 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
             compiler.registers(),
             compiler.assembler(),
             lambda_cc.get_computation(),
-            default_a_cc.get_computation(),
+            secondary_default_cc.get_computation(),
+            secondary_collection_cc.get_address(),
+            main_default_cc.get_computation(),
             holder.get_address(),
-            default_b_cc.get_computation(),
-            in_collection_b_cc.get_address(),
-            collection_cc.get_address(),
+            main_collection_cc.get_address(),
             (
                (tonkadur.fate.v1.lang.type.CollectionType)
-               n.get_collection().get_type()
+               n.get_main_collection().get_type()
             ).is_set(),
             params
          )
       );
 
-      collection_cc.release_registers(result);
-      in_collection_b_cc.release_registers(result);
-      default_a_cc.release_registers(result);
-      default_b_cc.release_registers(result);
+      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)
@@ -892,7 +897,7 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
    {
       /* This is one dangerous operation to do in-place, so we don't. */
 
-      if (n.get_default_a() != null)
+      if (n.get_main_default() != null)
       {
          visit_merge_with_defaults(n);
          return;
@@ -902,7 +907,7 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
       final ComputationCompiler lambda_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler collection_cc, in_collection_b_cc;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
@@ -916,25 +921,29 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          result.add(lambda_cc.get_init());
       }
 
-      collection_cc = new ComputationCompiler(compiler);
+      main_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection().get_visited_by(collection_cc);
+      n.get_main_collection().get_visited_by(main_collection_cc);
 
-      if (collection_cc.has_init())
+      if (main_collection_cc.has_init())
       {
-         result.add(collection_cc.get_init());
+         result.add(main_collection_cc.get_init());
       }
 
       holder =
          compiler.registers().reserve
          (
-            collection_cc.get_computation().get_type(),
+            main_collection_cc.get_computation().get_type(),
             result
          );
 
       result.add
       (
-         new SetValue(holder.get_address(), collection_cc.get_computation())
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
       );
 
       result.add
@@ -943,18 +952,17 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          (
             compiler.registers(),
             compiler.assembler(),
-            collection_cc.get_address()
+            main_collection_cc.get_address()
          )
       );
 
+      secondary_collection_cc = new ComputationCompiler(compiler);
 
-      in_collection_b_cc = new ComputationCompiler(compiler);
-
-      n.get_collection_in_b().get_visited_by(in_collection_b_cc);
+      n.get_secondary_collection().get_visited_by(secondary_collection_cc);
 
-      if (in_collection_b_cc.has_init())
+      if (secondary_collection_cc.has_init())
       {
-         result.add(in_collection_b_cc.get_init());
+         result.add(secondary_collection_cc.get_init());
       }
 
       for
@@ -989,19 +997,19 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
             compiler.registers(),
             compiler.assembler(),
             lambda_cc.get_computation(),
+            secondary_collection_cc.get_address(),
             holder.get_address(),
-            in_collection_b_cc.get_address(),
-            collection_cc.get_address(),
+            main_collection_cc.get_address(),
             (
                (tonkadur.fate.v1.lang.type.CollectionType)
-               n.get_collection().get_type()
+               n.get_main_collection().get_type()
             ).is_set(),
             params
          )
       );
 
-      collection_cc.release_registers(result);
-      in_collection_b_cc.release_registers(result);
+      main_collection_cc.release_registers(result);
+      secondary_collection_cc.release_registers(result);
       compiler.registers().release(holder, result);
 
       for (final ComputationCompiler cc: param_cc_list)
@@ -1017,17 +1025,18 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
    throws Throwable
    {
       final Register holder;
-      final ComputationCompiler lambda_cc, default_a_cc, default_b_cc;
+      final ComputationCompiler lambda_cc;
+      final ComputationCompiler main_default_cc, secondary_default_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler collection_cc, in_collection_b_cc;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
 
       lambda_cc = new ComputationCompiler(compiler);
-      default_a_cc = new ComputationCompiler(compiler);
-      default_b_cc = new ComputationCompiler(compiler);
+      main_default_cc = new ComputationCompiler(compiler);
+      secondary_default_cc = new ComputationCompiler(compiler);
 
       n.get_lambda_function().get_visited_by(lambda_cc);
 
@@ -1036,43 +1045,47 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          result.add(lambda_cc.get_init());
       }
 
-      collection_cc = new ComputationCompiler(compiler);
+      main_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection().get_visited_by(collection_cc);
+      n.get_main_collection().get_visited_by(main_collection_cc);
 
-      if (collection_cc.has_init())
+      if (main_collection_cc.has_init())
       {
-         result.add(collection_cc.get_init());
+         result.add(main_collection_cc.get_init());
       }
 
-      n.get_default_a().get_visited_by(default_a_cc);
+      n.get_main_default().get_visited_by(main_default_cc);
 
-      default_a_cc.generate_address();
+      main_default_cc.generate_address();
 
-      if (default_a_cc.has_init())
+      if (main_default_cc.has_init())
       {
-         result.add(default_a_cc.get_init());
+         result.add(main_default_cc.get_init());
       }
 
-      n.get_default_b().get_visited_by(default_b_cc);
+      n.get_secondary_default().get_visited_by(secondary_default_cc);
 
-      default_b_cc.generate_address();
+      secondary_default_cc.generate_address();
 
-      if (default_b_cc.has_init())
+      if (secondary_default_cc.has_init())
       {
-         result.add(default_b_cc.get_init());
+         result.add(secondary_default_cc.get_init());
       }
 
       holder =
          compiler.registers().reserve
          (
-            collection_cc.get_computation().get_type(),
+            main_collection_cc.get_computation().get_type(),
             result
          );
 
       result.add
       (
-         new SetValue(holder.get_address(), collection_cc.get_computation())
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
       );
 
       result.add
@@ -1081,17 +1094,17 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          (
             compiler.registers(),
             compiler.assembler(),
-            collection_cc.get_address()
+            main_collection_cc.get_address()
          )
       );
 
-      in_collection_b_cc = new ComputationCompiler(compiler);
+      secondary_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection_in_b().get_visited_by(in_collection_b_cc);
+      n.get_secondary_collection().get_visited_by(secondary_collection_cc);
 
-      if (in_collection_b_cc.has_init())
+      if (secondary_collection_cc.has_init())
       {
-         result.add(in_collection_b_cc.get_init());
+         result.add(secondary_collection_cc.get_init());
       }
 
       for
@@ -1126,23 +1139,23 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
             compiler.registers(),
             compiler.assembler(),
             lambda_cc.get_computation(),
-            default_a_cc.get_computation(),
+            secondary_default_cc.get_computation(),
+            secondary_collection_cc.get_address(),
+            main_default_cc.get_computation(),
             holder.get_address(),
-            default_b_cc.get_computation(),
-            in_collection_b_cc.get_address(),
-            collection_cc.get_address(),
+            main_collection_cc.get_address(),
             (
                (tonkadur.fate.v1.lang.type.CollectionType)
-               n.get_collection().get_type()
+               n.get_main_collection().get_type()
             ).is_set(),
             params
          )
       );
 
-      collection_cc.release_registers(result);
-      in_collection_b_cc.release_registers(result);
-      default_a_cc.release_registers(result);
-      default_b_cc.release_registers(result);
+      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)
@@ -1158,7 +1171,7 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
    )
    throws Throwable
    {
-      if (n.get_default_a() != null)
+      if (n.get_main_default() != null)
       {
          visit_indexed_merge_with_defaults(n);
          return;
@@ -1169,7 +1182,7 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
       final ComputationCompiler lambda_cc;
       final List<Computation> params;
       final List<ComputationCompiler> param_cc_list;
-      final ComputationCompiler collection_cc, in_collection_b_cc;
+      final ComputationCompiler main_collection_cc, secondary_collection_cc;
 
       params = new ArrayList<Computation>();
       param_cc_list = new ArrayList<ComputationCompiler>();
@@ -1183,25 +1196,29 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          result.add(lambda_cc.get_init());
       }
 
-      collection_cc = new ComputationCompiler(compiler);
+      main_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection().get_visited_by(collection_cc);
+      n.get_main_collection().get_visited_by(main_collection_cc);
 
-      if (collection_cc.has_init())
+      if (main_collection_cc.has_init())
       {
-         result.add(collection_cc.get_init());
+         result.add(main_collection_cc.get_init());
       }
 
       holder =
          compiler.registers().reserve
          (
-            collection_cc.get_computation().get_type(),
+            main_collection_cc.get_computation().get_type(),
             result
          );
 
       result.add
       (
-         new SetValue(holder.get_address(), collection_cc.get_computation())
+         new SetValue
+         (
+            holder.get_address(),
+            main_collection_cc.get_computation()
+         )
       );
 
       result.add
@@ -1210,17 +1227,17 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
          (
             compiler.registers(),
             compiler.assembler(),
-            collection_cc.get_address()
+            main_collection_cc.get_address()
          )
       );
 
-      in_collection_b_cc = new ComputationCompiler(compiler);
+      secondary_collection_cc = new ComputationCompiler(compiler);
 
-      n.get_collection_in_b().get_visited_by(in_collection_b_cc);
+      n.get_secondary_collection().get_visited_by(secondary_collection_cc);
 
-      if (in_collection_b_cc.has_init())
+      if (secondary_collection_cc.has_init())
       {
-         result.add(in_collection_b_cc.get_init());
+         result.add(secondary_collection_cc.get_init());
       }
 
       for
@@ -1255,19 +1272,19 @@ implements tonkadur.fate.v1.lang.meta.InstructionVisitor
             compiler.registers(),
             compiler.assembler(),
             lambda_cc.get_computation(),
+            secondary_collection_cc.get_address(),
             holder.get_address(),
-            in_collection_b_cc.get_address(),
-            collection_cc.get_address(),
+            main_collection_cc.get_address(),
             (
                (tonkadur.fate.v1.lang.type.CollectionType)
-               n.get_collection().get_type()
+               n.get_main_collection().get_type()
             ).is_set(),
             params
          )
       );
 
-      collection_cc.release_registers(result);
-      in_collection_b_cc.release_registers(result);
+      main_collection_cc.release_registers(result);
+      secondary_collection_cc.release_registers(result);
       compiler.registers().release(holder, result);
 
       for (final ComputationCompiler cc: param_cc_list)
diff --git a/src/core/src/tonkadur/wyrd/v1/compiler/util/IndexedMergeLambda.java b/src/core/src/tonkadur/wyrd/v1/compiler/util/IndexedMergeLambda.java
index e1e4e4f..818fde6 100644
--- a/src/core/src/tonkadur/wyrd/v1/compiler/util/IndexedMergeLambda.java
+++ b/src/core/src/tonkadur/wyrd/v1/compiler/util/IndexedMergeLambda.java
@@ -201,17 +201,22 @@ public class IndexedMergeLambda
       final List<Computation> extra_params
    )
    {
-      final List<Instruction> result, while_body;
-      final Register iterator_a, iterator_b;
+      final List<Instruction> result, while_body, oob_a_body, oob_b_body;
+      final Register iterator_a, iterator_b, oob_a, oob_b;
       final Register collection_a_size, collection_b_size;
       final Register storage;
 
       result = new ArrayList<Instruction>();
       while_body = new ArrayList<Instruction>();
+      oob_a_body = new ArrayList<Instruction>();
+      oob_b_body = new ArrayList<Instruction>();
 
       iterator_a = registers.reserve(Type.INT, result);
       iterator_b = registers.reserve(Type.INT, result);
 
+      oob_a = registers.reserve(Type.BOOL, result);
+      oob_b = registers.reserve(Type.BOOL, result);
+
       collection_a_size = registers.reserve(Type.INT, result);
       collection_b_size = registers.reserve(Type.INT, result);
 
@@ -243,16 +248,39 @@ public class IndexedMergeLambda
          )
       );
 
-      extra_params.add
+      result.add
       (
-         0,
-         new IfElseComputation
+         new SetValue
          (
-            Operation.less_than
+            oob_a.get_address(),
+            Operation.greater_equal_than
+            (
+               iterator_a.get_value(),
+               collection_a_size.get_value()
+            )
+         )
+      );
+
+      result.add
+      (
+         new SetValue
+         (
+            oob_b.get_address(),
+            Operation.greater_equal_than
             (
                iterator_b.get_value(),
                collection_b_size.get_value()
-            ),
+            )
+         )
+      );
+
+      extra_params.add
+      (
+         0,
+         new IfElseComputation
+         (
+            oob_b.get_value(),
+            default_b,
             new ValueOf
             (
                new RelativeAddress
@@ -263,8 +291,7 @@ public class IndexedMergeLambda
                      (MapType) collection_in_b.get_target_type()
                   ).get_member_type()
                )
-            ),
-            default_b
+            )
          )
       );
 
@@ -275,11 +302,8 @@ public class IndexedMergeLambda
          0,
          new IfElseComputation
          (
-            Operation.less_than
-            (
-               iterator_a.get_value(),
-               collection_a_size.get_value()
-            ),
+            oob_a.get_value(),
+            default_a,
             new ValueOf
             (
                new RelativeAddress
@@ -290,8 +314,7 @@ public class IndexedMergeLambda
                      (MapType) collection_in_a.get_target_type()
                   ).get_member_type()
                )
-            ),
-            default_a
+            )
          )
       );
 
@@ -324,7 +347,7 @@ public class IndexedMergeLambda
          )
       );
 
-      while_body.add
+      oob_a_body.add
       (
          new SetValue
          (
@@ -333,7 +356,20 @@ public class IndexedMergeLambda
          )
       );
 
-      while_body.add
+      oob_a_body.add
+      (
+         new SetValue
+         (
+            oob_a.get_address(),
+            Operation.greater_equal_than
+            (
+               iterator_a.get_value(),
+               collection_a_size.get_value()
+            )
+         )
+      );
+
+      oob_b_body.add
       (
          new SetValue
          (
@@ -342,31 +378,56 @@ public class IndexedMergeLambda
          )
       );
 
+      oob_b_body.add
+      (
+         new SetValue
+         (
+            oob_b.get_address(),
+            Operation.greater_equal_than
+            (
+               iterator_b.get_value(),
+               collection_b_size.get_value()
+            )
+         )
+      );
+
+      while_body.add
+      (
+         If.generate
+         (
+            registers,
+            assembler,
+            Operation.not(oob_a.get_value()),
+            assembler.merge(oob_a_body)
+         )
+      );
+
+      while_body.add
+      (
+         If.generate
+         (
+            registers,
+            assembler,
+            Operation.not(oob_b.get_value()),
+            assembler.merge(oob_b_body)
+         )
+      );
+
       result.add
       (
          While.generate
          (
             registers,
             assembler,
-            Operation.or
-            (
-               Operation.less_than
-               (
-                  iterator_a.get_value(),
-                  collection_a_size.get_value()
-               ),
-               Operation.less_than
-               (
-                  iterator_b.get_value(),
-                  collection_b_size.get_value()
-               )
-            ),
+            Operation.not(Operation.and(oob_a.get_value(), oob_b.get_value())),
             assembler.merge(while_body)
          )
       );
 
       registers.release(iterator_a, result);
       registers.release(iterator_b, result);
+      registers.release(oob_a, result);
+      registers.release(oob_b, result);
       registers.release(collection_a_size, result);
       registers.release(collection_b_size, result);
       registers.release(storage, result);