Brackets, braces, parentheses, and other such creatures

An interesting story about a common task in text-manipulation done with TDD. The problem is stated as such: This aim of this challenge was to determine whether any given string has a legal bracket structure. Basically, make sure all the '(', '[', '{', and '<' have matching ')', ']', '}' and '>'. We also need to take nesting into account, so that "({)}" is incorrect, and "({}<{}>)" will pass.