Editing Scheme (programming language) (section)

===Shared namespace for procedures and variables===
In contrast to Common Lisp, all data and procedures in Scheme share a common namespace, whereas in Common Lisp [[Common Lisp#The function namespace|functions and data have separate namespaces]] making it possible for a function and a variable to have the same name, and requiring special notation for referring to a function as a value. This is sometimes known as the "[[Lisp-1 vs. Lisp-2]]" distinction, referring to the unified namespace of Scheme and the separate namespaces of Common Lisp.<ref>{{Cite news |last1=Gabriel |first1=Richard P. |author-link=Richard P. Gabriel |last2=Pitman |first2=Kent |author-link2=Kent Pitman |year=1988 |title=Technical Issues of Separation in Function Cells and Value Cells |volume=1 |pages=81–101 |work=LISP and Symbolic Computation |issue=1 |publication-date=June 1988 |url=http://www.nhplace.com/kent/Papers/Technical-Issues.html |access-date=2012-08-09 |doi=10.1007/BF01806178}}</ref>

In Scheme, the same primitives that are used to manipulate and bind data can be used to bind procedures. There is no equivalent of Common Lisp's <code>defun</code> and <code>#'</code> primitives.

<syntaxhighlight lang="Scheme">
;; Variable bound to a number:
(define f 10)
f
===> 10
;; Mutation (altering the bound value)
(set! f (+ f f 6))
f
===> 26
;; Assigning a procedure to the same variable:
(set! f (lambda (n) (+ n 12)))
(f 6)
===> 18
;; Assigning the result of an expression to the same variable:
(set! f (f 1))
f
===> 13
;; functional programming:
(apply + '(1 2 3 4 5 6))
===> 21
(set! f (lambda (n) (+ n 100)))
(map f '(1 2 3))
===> (101 102 103)
</syntaxhighlight>