# recursion – Recursive definition of the length of a string?

Strings are concatenations of characters. Therefore, any non-empty string $$w$$ has a first character $$x$$ and can be written as $$w = x w$$, or $$w$$ is the tail rope. It follows from the definition of the length of a chain that $$| w | = | x w & # 39; = | x | + | w & # 39; = 1 + | w & # 39;$$.