Option variable
modulus
Default value: false
When modulus
is a positive number p,
operations on rational numbers (as returned by rat
and related functions)
are carried out modulo p,
using the so-called "balanced" modulus system
in which n modulo p
is defined as
an integer k in [-(p-1)/2, ..., 0, ..., (p-1)/2]
when p is odd, or [-(p/2 - 1), ..., 0, ...., p/2]
when p is even,
such that a p + k
equals n for some integer a.
If expr is already in canonical rational expression (CRE) form when modulus
is reset,
then you may need to re-rat expr, e.g., expr: rat (ratdisrep (expr))
,
in order to get correct results.
Typically modulus
is set to a prime number.
If modulus
is set to a positive non-prime integer,
this setting is accepted, but a warning message is displayed.
Maxima will allow zero or a negative integer to be assigned to modulus
,
although it is not clear if that has any useful consequences.