出典:Wikipedia
出典:『Wikipedia』 (2011/08/11 02:12 UTC 版)
In mathematics, a function f from a set X to a set Y is surjective (or onto), or a surjection, if for every
there is an
with f(x) = y; that is, each element of Y can be obtained by applying f to some element of X. (There might be multiple elements of X that are turned into the same element of Y by applying f.)