Function

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.

Example

The function f(x)=x2 maps the set of integers to the set of natural numbers: f:Z→N.

References

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