The IsPermutation(s) command returns the value true if the string s is a permutation of its support, and returns the value false otherwise. A string is a permutation if, and only if, each character in the string occurs exactly once.

Note that, since there are only $255$ distinct characters (byte values), the Pigeon-Hole Principle implies that no string permutation can exceed $255$ characters in length.

If s is the empty string, the command returns true.

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.

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

$\mathrm{IsPermutation}\left(''''\right)$

$\mathrm{true}$

$\mathrm{IsPermutation}\left(''abc''\right)$

$\mathrm{true}$

$\mathrm{IsPermutation}\left(''abcba''\right)$

$\mathrm{false}$

$r≔\mathrm{rand}\left(1..10\right)\:$

$S≔\left\{\mathrm{seq}\right\}\left(\mathrm{Random}\left(r\left(\right)\,'\mathrm{lower}'\right)\,i=1..1000\right)\:$

$\mathrm{select}\left(\mathrm{IsPermutation}\mathbf{and}\mathrm{IsPalindrome}\,S\right)$

$\left\{''a''\,''b''\,''c''\,''d''\,''e''\,''f''\,''g''\,''h''\,''i''\,''j''\,''k''\,''l''\,''m''\,''n''\,''o''\,''p''\,''q''\,''r''\,''s''\,''t''\,''u''\,''v''\,''w''\,''x''\,''y''\,''z''\right\}$