The Exchange( s, m, n ) command exchanges characters m and n in the string s. The integers m and n must satisfy $1\le m,n\le \mathrm{length}\left(s\right)$.

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.

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

$\mathrm{Exchange}\left(''abc''\,1\,2\right)$

$''bac''$

$\mathrm{Exchange}\left(''abc''\,1\,3\right)$

$''cba''$

$\mathrm{Exchange}\left(''abc''\,3\,3\right)$

$''abc''$