The SortPermutation( los ) command returns a permutation $p$ that sorts the list los, that is, for which $\left[\mathrm{seq}\right]\left({\mathrm{los}}_{p_i}\,i=1..\mathrm{nops}\left(\mathrm{los}\right)\right)$ is equal to $\mathrm{sort}\left(\mathrm{los}\right)$. The sorting order is lexicographic.

The permutation returned by SortPermutation is represented as a list of the positive integers from $1$ to $\mathrm{nops}\left(\mathrm{los}\right)$.

Note that an empty list, which is vacuously a permutation, is returned if the input list los is empty.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$L≔\left[''b''\,''c''\,''a''\right]\:$

$p≔\mathrm{SortPermutation}\left(L\right)$

$p≔\left[3\,1\,2\right]$

$\mathrm{type}\left(p\,'\mathrm{permlist}'\right)$

$\mathrm{true}$

$\left[\mathrm{seq}\right]\left(L\left[p\left[i\right]\right]\,i=1..3\right)$

$\left[''a''\,''b''\,''c''\right]$

$\mathrm{sort}\left(L\right)$

$\left[''a''\,''b''\,''c''\right]$

$\mathrm{SortPermutation}\left(\left[\right]\right)$