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lex-vs-dyn-binding

CREATED BY chris • LAST EDITED BY chris 7686 days AGO

(define x 1)
(define (f x) (g 2))
(define (g y) (+ x y))
(f 5)

With static (lexical) binding, that function application results in 3 (as the 'x binding in the parameter list of 'f is valid only in the body of the function), whereas with dynamic binding it results in 7 (as the 'x binding is overwritten during the call to 'f and only restored to its original value afterwards). Static binding generally makes programs easier to understand, as the binding of each symbol can be determined by looking at the source text (this strong connection to which is the reason for the other name of the concept, lexical binding).

Example from the MIT Scheme Reference.