From 369fe9a772847a0ed13d9ef07f1e98c093b9ee07 Mon Sep 17 00:00:00 2001
From: Nathanael Sensfelder <SpamShield0@MultiAgentSystems.org>
Date: Sat, 29 Aug 2020 17:30:12 +0200
Subject: Adds Let to the parser.

---
 src/core/src/tonkadur/fate/v1/parser/FateLexer.g4  |  1 +
 src/core/src/tonkadur/fate/v1/parser/FateParser.g4 | 90 ++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4 b/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
index 96856c1..4684a3e 100644
--- a/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
+++ b/src/core/src/tonkadur/fate/v1/parser/FateLexer.g4
@@ -60,6 +60,7 @@ INDEX_OF_KW: L_PAREN ('index'US'of') SEP+;
 IS_MEMBER_KW: L_PAREN ('is'US'member'|'contains'|'has') SEP+;
 LOWER_EQUAL_THAN_KW: L_PAREN ('lower'US'equal'US'than'|'=<'|'<='|'le') SEP+;
 LOWER_THAN_KW: L_PAREN ('lower'US'than'|'<'|'lt') SEP+;
+LET_KW: L_PAREN 'let' SEP+;
 MINUS_KW: L_PAREN ('minus'|'-') SEP+;
 MIN_KW: L_PAREN ('min'('imum'?)) SEP+;
 MAX_KW: L_PAREN ('max'('imum'?)) SEP+;
diff --git a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4 b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
index da6ea7f..8bbd4d2 100644
--- a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
+++ b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
@@ -1590,6 +1590,67 @@ returns [List<Type> result]
    }
 ;
 
+let_variable_list
+returns [List<Cons<Variable, Computation>> result]
+@init
+{
+   Map<String, Variable> variables;
+
+   variables = LOCAL_VARIABLES.peekFirst();
+
+   $result = new ArrayList<Cons<Variable, Computation>>();
+}
+:
+   (
+      WS*
+      L_PAREN WS* new_reference_name WS+ value WS* R_PAREN
+      {
+         final Variable v;
+
+         v =
+            new Variable
+            (
+               CONTEXT.get_origin_at
+               (
+                  ($L_PAREN.getLine()),
+                  ($L_PAREN.getCharPositionInLine())
+               ),
+               ($value.result).get_type(),
+               ($new_reference_name.result)
+            );
+
+         if (variables.containsKey(v.get_name()))
+         {
+            ErrorManager.handle
+            (
+               new DuplicateLocalVariableException
+               (
+                  variables.get(v.get_name()),
+                  v
+               )
+            );
+         }
+
+         variables.put(v.get_name(), v);
+
+         $result.add(new Cons(v, ($value.result)));
+      }
+   )*
+   {
+   }
+;
+catch [final Throwable e]
+{
+   if ((e.getMessage() == null) || !e.getMessage().startsWith("Require"))
+   {
+      throw new ParseCancellationException(CONTEXT.toString() + ((e.getMessage() == null) ? "" : e.getMessage()), e);
+   }
+   else
+   {
+      throw new ParseCancellationException(e);
+   }
+}
+
 variable_list
 returns [VariableList result]
 @init
@@ -2364,6 +2425,35 @@ returns [Computation result]
          LOCAL_VARIABLES.pop();
       }
 
+   | LET_KW
+         L_PAREN WS* let_variable_list WS* R_PAREN
+         WS*
+         value
+         WS*
+      R_PAREN
+      {
+         final List<Cons<Variable, Computation>> let_list;
+
+         let_list = ($let_variable_list.result);
+
+         $result =
+            new Let
+            (
+               CONTEXT.get_origin_at
+               (
+                  ($LET_KW.getLine()),
+                  ($LET_KW.getCharPositionInLine())
+               ),
+               let_list,
+               ($value.result)
+            );
+
+         for (final Cons<Variable, Computation> entry: let_list)
+         {
+            LOCAL_VARIABLES.peekFirst().remove(entry.get_car().get_name());
+         }
+      }
+
    | math_expression
    {
       $result = ($math_expression.result);
-- 
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