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And now, let's distribute scalar-vector multiplies. 4*1,2 = -> 4*1,4*2.

Code Block

tree grammar Simplify;
options {
    tokenVocab=VecMath;      // use tokens from VecMath.g
    ASTLabelType=CommonTree; // we're using CommonTree nodes
    output=AST;              // build ASTs from input AST
    filter=true;             // tree pattern matching, rewrited mode
}

topdown
    :   ^('*' INT ^(VEC (e+=.)+)) -> ^(VEC ^('*' INT $e)+)
    ;

bottomup
    :  ^('*' a=. b=INT {$b.int==0}?) -> $b // x*0 -> 0
    ;

Give it a shot:

Code Block


        VecMathLexer lex = new VecMathLexer(input);
        CommonTokenStream tokens = new CommonTokenStream(lex);
        VecMathParser g = new VecMathParser(tokens);
        RuleReturnScope r = g.prog();   // launch parser by calling start rule
        CommonTree t = (CommonTree)r.getTree();   // get tree result
        System.out.println("Original tree: "+t.toStringTree());

        CommonTreeNodeStream nodes = new CommonTreeNodeStream(t);
        Simplify s = new Simplify(nodes);
        t = (CommonTree)s.downup(t);
        System.out.println("Simplified tree: "+t.toStringTree());

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