This may not be the case in an imperative language. E. lambda calculus WFF - well formed formulas. Originally described in 12 pages was simple. Now the common lisp manual in 1992 is over 100 pages long. A. Pure Lisp - no side effects only function calls.
Numbers evaluate to themselves and use integer and real math.
A literal atom also has an associated property list, proplist. Cond evaluates the s1's one by one until it finds one that does not eval to nil. P CS 343 Chapter 8 . .