A function `f`

is a mapping from a set `X`

to a set `Y`

written `f:X→Y`

.
The set `X`

is called the domain.
The set `Y`

is called the range or codomain.

The function `f(x)=x`

maps the set of integers to the set of natural numbers: ^{2}`f:Z→N`

.

L. R. Knudsen, M. J. B. Robshaw, *The Block Cipher Companion.* Springer, 2011.

Copyright © 2014 Barry Watson. All rights reserved.