IsUnit( r )
IsUnit( R, r )
In the first form IsUnit
returns true
if the ring element r is a
unit in its default ring (see DefaultRing). In the second form
IsUnit
returns true
if r is a unit in the ring R.
An element r is called a unit in a ring R, if r has an inverse in R.
gap> IsUnit( Integers, 2 ); false gap> IsUnit( Integers, -1 ); true
IsUnit
calls R.operations.IsUnit( R, r )
and returns the value.
The default function called this way is RingOps.IsUnit
, which tries to
compute the inverse of r with R.operations.Quotient( R, R.one,
r )
and returns true
if the result is not false
, and false
otherwise. Special categories of rings overlay this default function
with more efficient functions.
GAP 3.4.4