antlr-3.4/runtime/CSharp3/Sources/Antlr3.Runtime.Test/Composition/Reduce.g3

tree grammar Reduce;

options
{
    tokenVocab=VecMath;      
    ASTLabelType=CommonTree; 
    output=AST;              
    filter=true;             
    language=CSharp3;
}


@members 
{ 
   //public override IAstRuleReturnScope Topdown() { return topdown(); }
   public override IAstRuleReturnScope Bottomup() { return bottomup(); } 
} 


/** Rewrite: x+x to be 2*x, 2*x to be x<<1, x<<n<<m to be x<<(n+m) */
bottomup
    :  ^(PLUS i=INT j=INT {$i.int==$j.int}?) -> ^(MULT["*"] INT["2"] $j)
    |  ^(MULT x=INT {$x.int==2}? y=.)        -> ^(SHIFT["<<"] $y INT["1"])
    |  ^(SHIFT ^(SHIFT e=. n=INT) m=INT)
       -> ^(SHIFT["<<"] $e INT[($n.int+$m.int).ToString()])
    ;