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prologswapslash

swap function in prolog

I need to replace the term A/B in prolog with B/A.

A and B are variables (could be either a number, an uppercase letter, or a lowercase letter)

I mean, what is on the right side of the slash should be on the left side and vice versa.

Examples:
A/10 should be 10/A
9/3 should be 3/9
5/B should be B/5

I hope it is clear. thanks.

Solution

  • really simple:

    swap(X/Y, Y/X).

    or could use unification 'inline', here a sample:

    ?- forall(member(A, [a/3, b/6]), (A=X/Y, B=Y/X, writeln(B))).
3/a
6/b
true.