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  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  is returned. If the length of s is less than len, then an empty string is returned.

Take and Drop satisfy the equation

for all non-negative integers n.