The Take(s, len) command returns the prefix of length len from string s.

If s has at least len characters, then the substring of s consisting of the first len characters of s is returned. That is, the string $s_{1..\mathrm{len}}$ is returned. If s has length less than len, then s is returned.

The Drop(s, len) command removes the prefix of length len from string s.

If the length of s is greater than or equal to len, then the string $s_{1+\mathrm{len}..\mathrm{-1}}$ is returned. If the length of s is less than len, then an empty string is returned.

If the second argument is a string delim, it is interpreted as a set of delimiting characters. In this case, the Take( s, delim ) command returns the prefix of s consisting of characters not in the string delim. The Drop( s, delim ) command returns the suffix of s consisting of characters not in the string delim.

Take and Drop satisfy the equation

for all non-negative integers n.

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.

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

$\mathrm{seq}\left(\mathrm{Take}\left(''abcde''\,i\right)\,i=0..6\right)$

$'''',''a'',''ab'',''abc'',''abcd'',''abcde'',''abcde''$

$\mathrm{seq}\left(\mathrm{Take}\left(''''\,i\right)\,i=0..6\right)$

$'''','''','''','''','''','''',''''$

$\mathrm{seq}\left(\mathrm{Drop}\left(''abcde''\,i\right)\,i=0..6\right)$

$''abcde'',''bcde'',''cde'',''de'',''e'','''',''''$

$\mathrm{seq}\left(\mathrm{Drop}\left(''''\,i\right)\,i=0..6\right)$

$'''','''','''','''','''','''',''''$

$\mathrm{seq}\left(\mathrm{cat}\left(\mathrm{Take}\left(''abcde''\,i\right)\,\mathrm{Drop}\left(''abcde''\,i\right)\right)\,i=0..6\right)$

$''abcde'',''abcde'',''abcde'',''abcde'',''abcde'',''abcde'',''abcde''$

$\mathrm{Take}\left(''abcde''\,''ec''\right)$

$''ab''$

$\mathrm{Drop}\left(''abcde''\,''ec''\right)$