In
mathematics, a bijection, or a bijective function is a
function f from a
set X to a set Y with the property that, for every y in Y, there is exactly one x in X such that f(x) = y.Alternatively, f is bijective if it is a one-to-one correspondence between those sets;
i.e., both one-to-one (
injective) and onto (
surjective). (See also
Bijection, injection and surjection.)For example, consider the function succ, defined from the set of
integers to , that to each integer x associates the integer succ(x) = x + 1. For another example, consider the function sumdif that to each pair (x,y) of real numbers associates the pair sumdif(x,y) = (x + y, x − y).
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