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c#dsloperator-precedenceirony
DanielR
DanielR

Reputation: 724

Irony .NET: Expression operator precedence

I'm using Irony to parse a DSL, which has expressions that can be combined with ANDs and ORs:

/* snip */

RegisterOperators(4, orKeyword);
RegisterOperators(5, andKeyword);
RegisterOperators(9, lessThanOperator, lessEqualOperator, equalOperator, notEqualOperator, moreThanOperator, moreEqualOperator);

infixOperator.Rule = andKeyword | orKeyword;
expression_in_parens.Rule = L_PAR + expression + R_PAR;
primaryExpression.Rule = expression_in_parens | methodCall | identifier | numberIdentifier | stringIdentifier;
unaryExpression.Rule = notKeyword + L_PAR + expression + R_PAR;
binaryExpression.Rule = expression + infixOperator + expression;
compareExpression.Rule = expression + compareOperator + expression + ReduceHere();
expression.Rule = primaryExpression | unaryExpression | compareExpression | binaryExpression;

I have the following expression: "A and (B and C or D)". It's parsed as "A and (B and (C or D))", but I need it to be "A and ((B and C) or D)".

I thought registering the and keyword as an operator with a higher priority than the or keyword would do that. What am I missing?

Upvotes: 2

Views: 1139

Answers (2)

Anton
Anton

Reputation: 1

Irony parser checks precedence of operators in terminals orKeyword, andKeyword. But there is nonterminal infixOperator without precedence. So, you have set transient for it: MarkTransient(infixOperator).

Upvotes: 0

DanielR
DanielR

Reputation: 724

I got it working by creating separate rules for AND and OR, and putting those in the right order:

binaryAndExpression.Rule = expression + andKeyword + expression;
binaryOrExpression.Rule = expression + orKeyword + expression;
compareExpression.Rule = expression + compareOperator + expression + ReduceHere();
expression.Rule = compareExpression | binaryAndExpression | binaryOrExpression | unaryExpression | primaryExpression;

Upvotes: 1

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