"returns" is not used in this way in logic programming. "return"
suggests that something went away and is now coming back, but this is
never the case in these situations. The arguments may be variables or
also fully known at the time of the call in most cases.
This reverts commit e185b626bd.
This change is now no longer needed, and the underlying issue is
apparently somewhere else entirely. See the description at:
https://github.com/mthom/scryer-prolog/issues/2732
Current master behaves differently from Scryer as it was at
099d9aaca6 (i.e., preceding
the commit that is now being reverted), even on the same file.
For an example, see:
dd41176b97
Scryer now works as expected, and compatibly with SICStus. We still
need to find out what fixed the root cause of this issue.
Some DCG constructs aren't supported and can't be expanded, here we
remove offending DCG rule and don't compile it at all – in a similar
fashion to what we do when incorrect goal was found – whole predicate
isn't getting compiled.
Fixes#2675
Examples:
?- portray_clause(((+) :- a=b,(-))).
(+) :-
a=b,
(-).
true.
?- portray_clause((a :- (b :- c))).
a :-
(b:-c).
true.
This addresses #2715.
Currently, more round brackets than needed are emitted. Ideally, a
better approach to solve the issue here and also in toplevel.pl is
found in the future.
This addresses #2713. Many thanks to @notoria for reporting this
excellent case!
Example:
?- portray_clause(A = @).
A= @ .
true.
At other positions the now inserted space is unnecessary, as in:
?- portray_clause((head:- @,b)).
head :-
@ ,
b.
true.
The toplevel has a similar issue:
?- C = # ; false.
C = # |<-- cursor is here; redundant space after #
There may be a way to solve this issue for all cases like this.
