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Rename precedence to resolve confusion #54

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Nov 30, 2023
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Rename precedence to resolve confusion #54

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7 changes: 4 additions & 3 deletions parser.y
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Original file line number Diff line number Diff line change
Expand Up @@ -79,8 +79,9 @@ extern std::unique_ptr<AstNode> program;
// ↳ 13: IF '(' expr ')' stmt •
//
// Our goal is to find the closest IF for ELSE, so we tell Yacc to shift.
// ELSE has a higher precendence than IF due to increasing precedence order.
%precedence IF
// Since the token "ELSE" has a higher precedence than the production rule
// "if without else", Yacc shifts to "ELSE" instead of reducing with the rule.
%precedence IF_WITHOUT_ELSE
%precedence ELSE

%start entry
Expand Down Expand Up @@ -127,7 +128,7 @@ stmt: ';' { $$ = std::make_unique<NullStmtNode>(); }
| RETURN expr ';' { $$ = std::make_unique<ReturnStmtNode>($2); }
| expr ';' { $$ = std::make_unique<ExprStmtNode>($1); }
| block { $$ = $1; }
| IF '(' expr ')' stmt %prec IF { $$ = std::make_unique<IfStmtNode>($3, $5); }
| IF '(' expr ')' stmt %prec IF_WITHOUT_ELSE { $$ = std::make_unique<IfStmtNode>($3, $5); }
| IF '(' expr ')' stmt ELSE stmt { $$ = std::make_unique<IfStmtNode>($3, $5, $7); }
;

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