Can't figure out how to resolve reduce/reduce conflict

I'm trying to create grammar for GNU MathProg language from glpk package https://www3.nd.edu/~jeff/mathprog/glpk-4.47/doc/gmpl.pdf
Unfortunately grammar I've written so far is ambiguous. I don't know how to tell bison which branch of parsing tree is correct when some identifier is used. For example:

numericExpression : numericLiteral
              | identifier
              | numericFunctionReference
              | iteratedNumericExpression
              | conditionalNumericExpression
              | '(' numericExpression ')' %prec PARENTH
              | '-' numericExpression %prec UNARY
              | '+' numericExpression %prec UNARY
              | numericExpression binaryArithmeticOperator numericExpression
              ;

symbolicExpression : stringLiteral
               | symbolicFunctionReference
               | identifier
               | conditionalSymbolicExpression
               | '(' symbolicExpression ')'  %prec PARENTH
               | symbolicExpression '&' symbolicExpression
               ;

indexingExpression : '{' indexingEntries '}'
               | '{' indexingEntries ':' logicalExpression '}'
               ;

setExpression : literalSet
          | identifier
          | aritmeticSet
          | indexingExpression
          | iteratedSetExpression
          | conditionalSetExpression
          | '(' setExpression ')'  %prec PARENTH
          | setExpression setOperator setExpression
          ;


numericLiteral : INT
           | FLT
           ;

 linearExpression : identifier
             | iteratedLinearExpression
             | conditionalLinearExpression
             | '(' linearExpression ')'  %prec PARENTH
             | '-' linearExpression  %prec UNARY
             | '+' linearExpression  %prec UNARY
             | linearExpression '+' linearExpression
             | linearExpression '-' linearExpression
             | linearExpression '*' numericExpression
             | numericExpression '*' linearExpression
             | linearExpression '/' numericExpression
             ;

logicalExpression : numericExpression
              | relationalExpression
              | iteratedLogicalExpression
              | '(' logicalExpression ')'  %prec PARENTH
              | NOT logicalExpression %prec NEG
              | logicalExpression AND logicalExpression
              | logicalExpression OR logicalExpression
              ;

identifier : SYMBOLIC_NAME
       | SYMBOLIC_NAME '[' listOfIndices ']'
       ;

listOfIndices : SYMBOLIC_NAME
    | listOfIndices ',' SYMBOLIC_NAME
    ;

Identifier is simply name of 'variable'. Variable has a specific type (parameter, set, decision variable) and might be indexed. In code programmer has to declare variable type in statements like eg.

param p1;
param p2{1, 2} >=0;
set s1;
set s2{i in 1..5};
var v1 >=0;
var v2{S1,S2};

But when bison sees identifier doesn't know which rule should use and i'm getting reduce/reduce conflicts like

113 numericExpression: identifier .
123 symbolicExpression: identifier .

'&'          reduce using rule 123 (symbolicExpression)
ELSE         reduce using rule 113 (numericExpression)
ELSE         [reduce using rule 123 (symbolicExpression)]
INTEGER      reduce using rule 113 (numericExpression)
INTEGER      [reduce using rule 123 (symbolicExpression)]
BINARY       reduce using rule 113 (numericExpression)
BINARY       [reduce using rule 123 (symbolicExpression)]
ASIGN        reduce using rule 113 (numericExpression)
ASIGN        [reduce using rule 123 (symbolicExpression)]
','          reduce using rule 113 (numericExpression)
','          [reduce using rule 123 (symbolicExpression)]
'>'          reduce using rule 113 (numericExpression)
'>'          [reduce using rule 123 (symbolicExpression)]
'}'          reduce using rule 113 (numericExpression)
'}'          [reduce using rule 123 (symbolicExpression)]

113 numericExpression: identifier .
123 symbolicExpression: identifier .
130 setExpression: identifier .

UNION           reduce using rule 130 (setExpression)
DIFF            reduce using rule 130 (setExpression)
SYMDIFF         reduce using rule 130 (setExpression)
ELSE            reduce using rule 113 (numericExpression)
ELSE            [reduce using rule 123 (symbolicExpression)]
ELSE            [reduce using rule 130 (setExpression)]
WITHIN          reduce using rule 130 (setExpression)
IN              reduce using rule 113 (numericExpression)
IN              [reduce using rule 123 (symbolicExpression)]

I have also other problems but this one is blocker for me

Solution

Basically the problem is that identifier appears in multiple rules:

numericExpression : identifier
symbolicExpression : identifier
setExpression: identifier

which may apply in the same context. One way to resolve this is to introduce different token types for set names and scalar (parameters and variables) names:

symbolicExpression : SCALAR_NAME
setExpression: SET_NAME

This will resolve conflict with set names. I don't think that you need this rule

numericExpression : identifier

because there is an automatic conversion from strings to numbers in AMPL and therefore MathProg, which is a subset of AMPL, so symbolicExpression should be allowed in the context of numericExpression.

Note that the grammar is not context-free, so you'll need to pull additional information like the name category above from the symbol table to resolve problems like this.

My flex is a bit rusty but I think you can do something like that in an identifier rule:

return is_setname(...) ? TOK_SET_NAME : TOK_SCALAR_NAME;

where is_setname is a function to check whether the current identifier is a set. You'll need to define such function and get the necessary information from a symbol table.