|
Posted
almost 11 years
ago
by
schneiderr
I am currently working on some pseudoMDX expression parser and I got stucked.
I got reduce-reduce conflict which I don't know why occurs.
Here is my simplified grammar:
internal class CG : Grammar
{
public CG()
: base(false)
{
... [More]
//terminals
var integer = new NumberLiteral("integer", NumberOptions.IntOnly);
var mdxIdentifier = new StringLiteral("mdxIdentifier");
mdxIdentifier.AddStartEnd("[", "]", StringOptions.None);
//nonTerminals
var expression = new NonTerminal("expression");
var numOperation = new NonTerminal("numOperation");
var numOperator = new NonTerminal("numOperator");
var expressionItem = new NonTerminal("expressionItem");
var memberFromExpression = new NonTerminal("memberFromExpression");
var memberForItemFunction = new NonTerminal("memberForItemFnc");
var member = new NonTerminal("member");
var itemFunction = new NonTerminal("itemFunction");
expression.Rule =
numOperation
| expressionItem
| "(" + expression + ")";
numOperation.Rule = expression + numOperator + expression;
numOperator.Rule = ToTerm("+") | "-" | "/" | "*";
expressionItem.Rule =
memberFromExpression
//| lots of other rules
;
memberFromExpression.Rule =
member
| "{" + memberFromExpression + "}"
| "(" + memberFromExpression + PreferShiftHere() + ")"
//lots of other rules
;
memberForItemFunction.Rule =
member
| "{" + memberForItemFunction + "}"
//lots of other rules
;
member.Rule =
mdxIdentifier
| itemFunction
//lots of other rules
;
itemFunction.Rule =
memberForItemFunction + "." + "item" + "(" + integer + ")"
//| memberFromExpression + "." + "item" + "(" + integer + ")"
;
Root = expression;
RegisterOperators();
}
private void RegisterOperators()
{
RegisterOperators(40, "+", "-");
RegisterOperators(50, "*", "/");
}
}
I can't catch the point why there is conflict.
Reduce-reduce conflicts on inputs: }
Reduce items:
membersFromExpression -> member · [EOF + - / * } )]
memberForItemFunction -> member · [. }]
Transitions:
Well, OK they may look the same i.e. "{[Member]}", but thy both exist in different context so I don't think they are ambigious.
Using Reduce hint wont help because
memberForItemFunction.Rule =
member + ReduceHere()
| "{" + memberForItemFunction + "}"
//lots of other rules
;
would not parse expression like "{[Member]}" as memberFromExpression.
And using Reduce hint for memberFromExpression would not parse expression "{[Member]}.item(7)" because it would not identify "{[Member]}" as memberForItemFunction.
It there any way how to solve this?
[Less]
|
