Symbols
We have already been using symbols. define associates a symbol with a value.
(define pi 3.1415926535)In Lisp, unlike most languages, symbols and structures of symbols can be manipulated at runtime. This is a unique source of the power of Lisp. We can use symbolic structures for:
(define phone-list '((john 3271234) (mary 4440101)))
(define form-letter '(dear mr name)) (define opt-patterns '( (= (- x x) 0) )) (define formula '(= f (* m a)))
(define rules '((all x (if (human x) (mortal x)))))
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