Dear GAP Forum,

Saad Belawi asked:

saadchina@maktoob.com said:
> Let L be a list of integers, is there a way to test whether each
> member of L is a power of a specific prime, it seems that the command
> "IsPrimePowerInt" do that but for an arbitrary prime

A reasonably efficient and simple solution is

IsPowerOfP := function(n,p)
return n mod p = 0 and IsPrimePowerInt(p);
end;

Then for instance, set p and then do:

Filtered(L, n->IsPowerOfP(n,p));

will give you the list of all powers of p in L.

Steve

-- 
Steve Linton	School of Computer Science  &
      Centre for Interdisciplinary Research in Computational Algebra
	     University of St Andrews 	 Tel   +44 (1334) 463269
http://www.dcs.st-and.ac.uk/~sal	 Fax   +44 (1334) 463278   

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