GPPG (bison) - How to implement an "expression expression" concept

We're using GPPG (essentially bison for C#) to generate a parser for a programming language. Everything is going great except for one really nasty bit. The language we are parsing has a sort of "implicit comparison" rule, where "expression expression" should be interpreted as "expression == expression".

For example, this is a perfectly valid statement:

 If SomeValue False Then
 EndIf

This obviously introduces all sorts of conflicts during parser generation. My f开发者_StackOverflowirst attempt at solving them went something along these lines (edited for brevity). I tried to do some refactoring of the rules, and it doesn't seem to be ambiguous anymore, but I must just be missing something obvious.

Here is a very small grammar that shows the conflict I'm having, and how I've attempted to solve it, doesn't work though

%start program
%token <Token> Plus
%token <Token> Times
%token <Constant> Constant

%left Plus
%left Times
%left IMPLICIT_COMPARISON

%%

program: expression;

expressionBase: Constant
    | expression Plus expression
    | expression Times expression;

expression: expressionBase
    | expression expressionBase %prec IMPLICIT_COMPARISON;

%%

Any help would be greatly appreciated

How about this:

program: expression;

expressionBase: Constant
    | expressionBase Plus expressionBase
    | expressionBase Times expressionBase;

expression: expressionBase 
    | expressionBase expression;

You need to build the grammar from bottom to top, not mixing your low-level concepts (like expressionBase) amd high-level ones (like expression). The high-level ones are build with the low-level ones. If you need it the other way around, you have to clearly delimit the high-level concept with parentheses or some such, like below:

expressionBase: Constant
    | expressionBase Plus expressionBase
    | expressionBase Times expressionBase
    | LeftParen expression RightParen;

The actual rules are rather more complicated but this should get you started.