I have defined the following production rules for expressions. The grammar is not allowed to have backtracking and k better or equal to 3. The current version seams to have some ambiguity, but I can't figure out where. I've removed the AST rules here, but the grammar is supposed to create a nice AST where operations are presented according to their priority as well as showing the left associativity of operations.
Antlr 3.2.1 with Antlerworks 1.5.1
disjunctionExpresion
: (conjunctionExpresion Disjunction conjunctionExpresion disjunctionExpresionDash) | conjunctionExpresion;
disjunctionExpresionDash
: (Disjunction conjunctionExpresion disjunctionExpresionDash) |;
conjunctionExpresion
: (relationalExpresion Conjunction relationalExpresion conjunctionExpresionDash) | relationalExpresion;
conjunctionExpresionDash
: (Conjunction relationalExpresion conjunctionExpresionDash)|;
relationalExpresion
: (addExpresion RelationalOperator addExpresion relationalExpresionDash) | addExpresion;
relationalExpresionDash
: (RelationalOperator addExpresion relationalExpresionDash)|;
addExpresion
: (multiExpresion addOperator multiExpresion addExpresionDash)| multiExpresion;
addExpresionDash
: (addOperator multiExpresion addExpresionDash)|;
multiExpresion
: (unaryExpresion MultiOperator unaryExpresion multiExpresionDash) | unaryExpresion;
multiExpresionDash
: (MultiOperator unaryExpresion multiExpresionDash) | ;
unaryExpresion
: (unaryOperator basicExpr)->^(unaryOperator basicExpr) | basicExpr -> basicExpr;
basicExpr
: Number | var basicExprDash | ('(' expr ')')->expr;
basicExprDash
: 'touches' var | ;
With @kaby76's hint of using EBNF and looking up example grammars, I have ended up with something similar to this C++ Antlr3 example. The Antrl3 Documentations for Tree construction was also very helpful.
The "^" quick operator allowed me to create the desired AST.
expr : disjunctionExpression;
disjunctionExpression
: conjunctionExpression (Disjunction^ conjunctionExpression)*;
/*equal to:
disjunctionExpression
: (a=conjunctionExpression->$a) (o=Disjunction b=conjunctionExpression -> ^($o $disjunctionExpression $b) )*;
*/
conjunctionExpression
: relationalExpression (Conjunction^ relationalExpression)*;
relationalExpression
: additiveExpression (relationalOperator^ additiveExpression)*;
additiveExpression
: multiExpression (addOperator^ multiExpression)*;
multiExpression
: unaryExpression (multiOperator^ unaryExpression)*;
unaryExpression
: (unaryOperator^)? basicExpr;
basicExpr
: Number | var ('touches'^ var)? | '(' expr ')' -> expr;
Which is actually the compact version of what I had before:
expr : disjunctionExpresion;
disjunctionExpresion
: conjunctionExpresion disjunctionExpresionDash;
disjunctionExpresionDash
: (Disjunction conjunctionExpresion disjunctionExpresionDash) |;