IsPrime( r )
IsPrime( R, r )
In the first form IsPrime
returns true
if the ring element r is a
prime in its default ring (see DefaultRing) and false
otherwise. In
the second form IsPrime
returns true
if the ring element r is a
prime in the ring R and false
otherwise.
An element r of a ring R is called prime if for each pair s and t such that r divides s t the element r divides either s or t. Note that there are rings where not every irreducible element (see IsIrreducible) is a prime.
gap> IsPrime( Integers, 4 ); false gap> IsPrime( Integers, 3 ); true
IsPrime
calls R.operations.IsPrime( R, r )
and returns the
value.
The default function called this way is RingOps.IsPrime
, which just
signals an error, because there is no generic way to test whether an
element is prime. Thus special categories of rings must overlay this
default function with other functions.
GAP 3.4.4