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Re: GMPL do not detect invalid subscript


From: Andrew Makhorin
Subject: Re: GMPL do not detect invalid subscript
Date: Wed, 12 Aug 2020 20:01:06 +0300

On Wed, 2020-08-12 at 19:44 +0300, Andrew Makhorin wrote:
> On Wed, 2020-08-12 at 17:33 +0200, Domingo Alvarez Duarte wrote:
> > Hello Andrew !
> > 
> > Thank you for reply !
> > 
> > That's the problem It should not work, the constraint "zumVariance: 
> > sum{z in Sample} E[z+10] = 0;" should give an error because when "z = 
> > last_valid_subscript - 9" the resulting expression will be 
> > "last_valid_subscript+1" and so on.
> 
> You declare E as
> 
>       var E{z in Sample};
> 
> so evaluating
> 
>       sum{z in Sample} E[z+10]
> 
> causes a domain (indexing) error as expected.
> 
> If, for example, Sample = {1..100}, the error will be detected on z = 91,
> since z + 10 = 101 is not in Sample.
> 

More precisely, the error will be detected on any 91 <= z <= 100, because
the order, in which sum enumerates elements from Sample, may be arbitrary.





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