Prolog what's the difference between \+ and \=

Question

What is the difference \= and \+?

because

?- 15\=14.
?- \+ 15=14.<--- this gives an error while the above does not.

Why?Aren't they the same?

Edit: here's the error:

Compiling the file:
D:\Program Files\Strawberry Prolog Beta\Games\WarCraft.pro
Warning 4: The string \+ is not an operator. (line 1, before the first clause)
Error 16: Instead of the integer 15 what is expected here is something like an infix operator or a full stop. (line 1, before the first clause)
1 error, 1 warning.

Also I'm using Strawberry prolog I also tried it on SWI prolog still the same.

Both work fine for me in SWI-Prolog (succeeding with true.). What Prolog are you using? What is the error message? Please edit the question to add this information. — Isabelle Newbie
Probably an operator precedence issue. Try \+ (15=14). Otherwise, it thinks you're trying to do \+ 15 followed by = 14 which would not make syntactic sense. — lurker

Isabelle Newbie Isabelle Newbie · Accepted Answer · 2018-05-22T20:27:12

I think you are putting queries into Prolog source files. That is not where they should go:

predicate definitions go into Prolog source files
queries are typed into the interactive Prolog toplevel

Try running the SWI-Prolog program without an input file. You should get a window with some informational messages about the SWI-Prolog version and then a prompt ?-. That is the toplevel. Try typing your query there. All queries should go there.

I don't know about Strawberry Prolog, but I suspect it's the same there.

Prolog what's the difference between \+ and \=

1 Answers