remainder, remainderf, remquo, and remquof return the remainder r := x - n*y where n is the integer nearest the exact value of
.Bk -words x / y;
.Ek moreover if \*(Ba n -
.Sm off x / y \*(Ba
.Sm on = 1/2 then n is even. Consequently the remainder is computed exactly and
.Sm off \*(Ba r \*(Ba
.Sm on <=
.Sm off \*(Ba y \*(Ba/2.
.Sm on But attempting to take the remainder when y is 0 or x is ±oo is an invalid operation that produces a NaN.
The remquo and remquof functions also store the last k bits of n in the location pointed to by quo, provided that n exists. The number of bits k is platform-specific, but is guaranteed to be at least 3.
fmod(3), ieee(3), math(3)