op(500,xfy,"aaa")?
op(500,xfy,123)?
op(500,xfy,123.3)?
op(500,xfy,A)?
;
op(500,xff,asd)?
op(5000,xfy,asd)?
op(0,xfy,asd)?
op(-234,xfy,asd)?
op(abc,xfy,asd)?
op(500,xfy,asd)?
A= quick asd fox?
B=root_sort(A)?
.

