11 ms·

In Prolog :- is the if operator.

• gumby 5y ago
  Its use is kind of a code smell, and I believe it was a relatively (prolog is old) late addition. In any case, I wrote "doesn't need", though perhaps you consider that hair splitting.
  • Avshalom 5y ago
    I think you misinterpreted that. Prolog does has an if operator -> as in ( P -> If ; Else ) yes, but oldsecondhand said :- "predicateA is true" if "clauseB is true" and "clauseC is true". or in prolog predicateA :- clauseB, clauseC. so :- is if, just in it's own, Prolog-y way.
    • AnimalMuppet 5y ago
      Is that an "if", though? In C/C++, you could write that as: if (clauseB && clauseC) predicateA = true; else predicateA = false; which is clearly an "if". Or you could write it as: predicateA = claseB && clauseC; which is not an "if" at all, but just a boolean calculation. (Unless you regard all boolean calculations as "if"s in disguise...) The prolog version seems to me to be more in the spirit of the second C version.
      • Avshalom 5y ago
        Well if nothing has any arguments then yeah, it's basically the second version. but if you had arguments you end up with things like %foo(+A,-B) foo(A,42) :- A < 10. foo(A,24) :- A >= 10. foo(_,100). which would be bool foo(int *A, int *B){ if (*A < 10){ *B = 42; }elseif (*A >= 10){ *B = 24; }else{ *B = 100; } return true; } /* my pointer knowledge is rusty though, so grain of salt */