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**Subject**:**Re: CVS commit: src/games/factor****From**:**David Laight <david%l8s.co.uk@localhost>**- Date: Sun, 16 May 2010 17:09:58 +0100

On Sun, May 16, 2010 at 11:37:43AM +0200, Martin Husemann wrote: > On Sun, May 16, 2010 at 09:54:49AM +0100, David Laight wrote: > > The notion of 'primes' is valid in Z - the definition of a prime is a > > number that has no non-unit factors. > > Well, I only took the forced (for CS students) math courses at university, > and it's been quite some time, but I would have defined a prime as a natural > number > 1. For what it's worth, wikipedia seems to agree with me ;-) > (duck) The definition of primality gets taken from that of the positive (or non-negative integers) and applied more generally to other mathematical objects - in particular 'fields'. In field theory you need a definition that applies to any field, not just the integers. From memory - it is a long time since I did any field theory - a field has a single 'zero', and possibly many 'units' (I think units are defined as values that multiplying by doesn't change the magnitude). For the field 'Z' (all the integers) the units are 1 and -1, and the mathematical definition of primality makes 'prime * unit' prime. David -- David Laight: david%l8s.co.uk@localhost

**Follow-Ups**:**Re: CVS commit: src/games/factor***From:*Dennis den Brok

**References**:**Re: CVS commit: src/games/factor***From:*David Laight

**Re: CVS commit: src/games/factor***From:*Martin Husemann

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