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Bill Allombert on Tue, 11 Oct 2016 18:54:58 +0200
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install and functions returning NULL
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- To: pari-dev@pari.math.u-bordeaux.fr
- Subject: install and functions returning NULL
- From: Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>
- Date: Tue, 11 Oct 2016 18:54:51 +0200
- Delivery-date: Tue, 11 Oct 2016 18:54:58 +0200
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Dear PARI developers,
I found an awful trick to be able to install C functions returning NULL:
NULL is used in the gp evaluator to denote missing arguments so
null0(a=0)=a
will convert NULL to 0.
For example:
install(Fp_sqrt,GG);
null0(a=0)=a;
mysqrt(a,b)=null0(Fp_sqrt(a,b));
? mysqrt(-1,7)
%4 = 0
? mysqrt(-3,7)
%5 = 2
Cheers,
Bill.