Changeset 1d71208 for src/Parser

Timestamp:

Jun 23, 2021, 4:59:37 PM (3 years ago)

Author:

Michael Brooks <mlbrooks@…>

Branches:

ADT, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum

Children:

27434e9

Parents:

6448f7d

Message:

Implementing new-array subscripting syntax, in which a[x,y,z] now means the same as ax,y,z?.

This behaviour immediately replaces a syntax error that prohibits the -[-,-,-] syntax. The prior state showed that the C programs we compile don't use the C-compatible meaning of commas in subscripts.

This behaviour ultimately replaces the C-compatible interpretation in which a[x,y,z] means a[(x,y,z)] or, roughly, ({ x; y; a[z]; }).

File:

• src/Parser/parser.yy (modified) (1 diff)

src/Parser/parser.yy

@@ -635 +635 @@
 postfix_expression:
         primary_expression
-        | postfix_expression '[' assignment_expression ',' comma_expression ']'
-                // { $$ = new ExpressionNode( build_binary_val( OperKinds::Index, $1, new ExpressionNode( build_binary_val( OperKinds::Index, $3, $5 ) ) ) ); }
-                { SemanticError( yylloc, "New array subscript is currently unimplemented." ); $$ = nullptr; }
+        | postfix_expression '[' assignment_expression ',' tuple_expression_list ']'
+                        // Historic, transitional: Disallow commas in subscripts.
+                        // Switching to this behaviour may help check if a C compatibilty case uses comma-exprs in subscripts.
+                // { SemanticError( yylloc, "New array subscript is currently unimplemented." ); $$ = nullptr; }
+                        // Current: Commas in subscripts make tuples.
+                { $$ = new ExpressionNode( build_binary_val( OperKinds::Index, $1, new ExpressionNode( build_tuple( (ExpressionNode *)($3->set_last( $5 ) ) )) ) ); }
         | postfix_expression '[' assignment_expression ']'
                 // CFA, comma_expression disallowed in this context because it results in a common user error: subscripting a