private void ifproc(){
        mustbe(TK.IF);
        gcprint("if(");
        expression();
        gcprint(")");
        mustbe(TK.THEN);
        block();
        while( is(TK.ELSIF) ) {
            scan();
            gcprint("else if(");
            expression();
            gcprint(")");
            mustbe(TK.THEN);
            block();
        }
        if( is(TK.ELSE) ) {
            scan();
            gcprint("else");
            block();
        }
        mustbe(TK.END);
    }