[m-dev.] proposal for promise_pure scope warning

Peter Schachte schachte at csse.unimelb.edu.au
Tue Apr 15 16:43:25 AEST 2008

Ian MacLarty wrote:
> On Tue, Apr 15, 2008 at 01:50:48PM +1000, Peter Schachte wrote:

>> But the promise 
>> still might be correct.  The code might destructively modify some data 
>> structure in an equivalence-preserving way, eg caching the result of a 
>> computation.
> But then why wouldn't the called predicate be declared pure in the first
> place?

It could be a general impure predicate to update a data structure in place, 
but it might be used in this context to update a cache in an 
equality-preserving way.

Peter Schachte              It is the function of the citizen to keep the
schachte at cs.mu.OZ.AU        Government from falling into error.
www.cs.mu.oz.au/~schachte/      -- Robert H. Jackson
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