-- Option variable: modulus Default value:
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.
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.
(%o1) true (%i2)