## Permutations

This chapter describes functions for creating and manipulating
permutations. A permutation p is represented by an array of
n integers in the range 0 to n-1, where each value
p_i occurs once and only once. The application of a permutation
p to a vector v yields a new vector v' where
v'_i = v_{p_i}.
For example, the array (0,1,3,2) represents a permutation
which exchanges the last two elements of a four element vector.
The corresponding identity permutation is (0,1,2,3).

Note that the permutations produced by the linear algebra routines
correspond to the exchange of matrix columns, and so should be considered
as applying to row-vectors in the form v' = v P rather than
column-vectors, when permuting the elements of a vector.

The functions described in this chapter are defined in the header file
`gsl_permutation.h`

.