The following functions can be used to access and manipulate permutations.
This function returns the value of the i-th element of the
permutation p. If i lies outside the allowed range of 0 to
n-1 then the error handler is invoked and 0 is returned. An inline version of this function is used when
HAVE_INLINE is defined.
This function exchanges the i-th and j-th elements of the permutation p.