idiv(n, m) is integer division, with the same effect as
n %/% m. mod(n, m) is the modulo operator and returns $n mod m$.
mod(n, 0) is n, and the result always has the same sign
as m.
rem(n, m) is the same modulo operator and returns $n mod m$.
mod(n, 0) is NaN, and the result always has the same sign
as n.