Editing Late binding (section)

===Late binding in Lisp===
In [[Lisp (programming language)|Lisp]], late bound global function calls are efficiently looked up at runtime via a [[Symbol (programming)|symbol]]'s function cell. These function bindings are mutable.

Example using an interactive [[Clozure CL|Clozure Common Lisp]] session:

<syntaxhighlight lang="Lisp">
? (defun foo ()
    (bar pi))   ; a still undefined function BAR gets called
;Compiler warnings :
;   In FOO: Undefined function BAR
FOO

? (defun bar (x)   ; now we define it
    (* x 2))
BAR

? (foo)    ; calling foo and it uses the recent definition of BAR
6.283185307179586D0

? (defun bar (x)   ; now we redefine BAR
    (* x 1000))
BAR

? (foo)    ;  FOO now calls the new function, there is no need to recompile/link/load FOO
3141.592653589793D0

? (type-of 'bar)   ;  BAR is a symbol
SYMBOL

? (symbol-function 'bar)  ; the symbol BAR has a function binding
#<Compiled-function BAR #x302000D1B21F>

</syntaxhighlight>