We can use the LISP interpreter to compute the value of combinations of built-in functions and special forms applied to arguments, but to use LISP as a programming language rather than as a curious kind of calculator, we must have a way to define functions of our own choosing and use them, rather than just use unnamed compositions of preexisting functions.
The special form LAMBDA is used in LISP to create a user-defined function. LAMBDA takes two arguments, which are both S-expressions. The first argument is a list of ordinary atoms denoting the formal arguments ...
