[m-dev.] proposal for promise_pure scope warning

[Julien Fischer]

On Tue, 15 Apr 2008, Julien Fischer wrote:

>
> On Tue, 15 Apr 2008, Ian MacLarty wrote:
>
>> 
>> ( promise_pure ( impure p ) ->
>>    true
>> ;
>>    true
>> )
>> 
>> The same applies to the case where there is output, but the output is
>> not used.
>> 
>>> (Which is the "bug" I assume you are trying to address here)
>>> 
>> 
>> That is a symptom, but the underlying problem is that purity is being
>> promised away in the wrong spot.  A goal like:
>> 
>>    promise_pure ( impure p )
>> 
>> just makes no sense (regardless of the determinism), because either the
>> goal should be impure, or p itself should be pure.
>
> The G12 FD solver uses constructs like the above extensively (which
> is one reason I don't want any warning to be enabled by default).

Actually, calls to the automatically generated solver type casting
functions is another case where one may legitimatly have something of
the form:

 	promise_pure (impure p).

Julien.
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