hermann on Thu, 28 Aug 2025 20:16:41 +0200


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Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica? 

On 2025-08-28 19:59, Bill Allombert wrote:
On Thu, Aug 28, 2025 at 05:02:28PM +0200, hermann@stamm-wilbrandt.de wrote: 
Are you in the mood of adding another operator (!!) to GP?


Adding this one would break backward compatibility, so this is not
an option.

? 3!!
%1 = 720

Cheers,
Bill
Understood — but we live in a world of unicode since more than 3 decades now. 

Double exclamation mark is U+203C:
https://unicodeplus.com/U+203C

Current GP does not allow for it to be used as function name:

? ‼(x)=2*x;
*** syntax error, unexpected invalid token, expecting end of file: ‼(x)=2*x; *** ^----------- 
?

But you could add it as operator ...

Regards,

Hermann.