Re: Getting different results than Schrijvers

It really can't. Allowing unification there violates the basic theory of CHR.  The problem is that binding variables activates constraints, but we are in the middle of deciding whether to activate a constraint so doing so would be inconsistent.  Also not activating would be wrong.
The choices are 
a) prevent it, at a small performance cost (swi default)
b) tell people not to do it, and hope (yap default)


> On Apr 4, 2014, at 3:13 PM, Feliks Kluzniak <[email protected]> wrote:
> 
> 
>> The other one is a case of bad code.
>> 
>> neq(X,Y) <=> X \= Y | true.
>> 
>> This breaks one of the requirements of CHR: variables cannot be bound in
>> the guard.  Since X \= Y is \+ X = Y, the runtime is screwing up because
>> there is an attempt to unify. 
> 
> Most interesting!
> 
> But shouldn’t this be treated as an error in the implementation?  One can view it as a good example of a leaking interface.  People are sure to trip over this time and time again.
> 
> — Feliks
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