if (i1 == 0 || i2 == 0) { return null; }
    vDescriptor function(vDescriptor[] args) {	vCset c = vCset.argVal(args, 0);	vString s = iRuntime.argSubject(args, 1);	int i1 = s.posEq(iRuntime.argPos(args, 2));	int i2 = s.posEq(vInteger.argVal(args, 3, 0));	if (i1 > i2) {	    int tmp = i1;	    i1 = i2;	    i2 = tmp;	}	if (i1 < i2 && c.member(s.value.charAt(i1-1))) {	    return iNew.Integer(i1+1);	}	return null;    }