Hi!

I am trying to get Prolog code look more like FOL, and I used op/3 and term_expansion/2 to do this.

```
:- op(1200, xfx, ==>).
:- op(1000, xfy, /\).
:- op(1100, xfy, \/).
term_expansion(A ==> B, B:- A).
term_expansion(A /\ B, A, B).
term_expansion(A \/ B, A; B).
man(X) /\ unmarried(X) ==> bachelor(X).
man(john).
man(peter).
unmarried(john).
main:-bachelor(X), writeln(X), nl, fail.
```

But i get the error ERROR: bachelor/1: Undefined procedure: (/)/2

Exception: (5) man(_1740)/\unmarried(_1740) ?

Can anyone help? Thanks!