The Has( s, ch ) command determines whether the string s contains the character ch. It returns the value true if s contains ch, and false otherwise.

The string ch must not be the empty string. Furthermore, if the length of ch is greater than $1$, then characters in ch after the first are ignored.

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.

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

$\mathrm{Has}\left(''ABC''\,''A''\right)$

$\mathrm{true}$

$\mathrm{Has}\left(''ABC''\,''a''\right)$

$\mathrm{false}$

$\mathrm{Has}\left(''foo:bar''\,'':''\right)$

$\mathrm{true}$