One of the most important advantages of functional programming is that
it allows interactive testing. In purely functional code, you can test each
function as you write it. If it returns the values you expect, you can be
confident that it is correct. (查看原文)
What is Lambda?
The lambda in a lambda expression is not an operator. It is just a symbol.
In earlier dialects of Lisp it had a purpose: functions were represented
internally as lists, and the only way to tell a function from an ordinary list
was to check if the first element was the symbol lambda. (查看原文)
