define -- r7rs Definition
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Kind
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syntax;

Implemented by
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Syntax signature
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Syntax keywords:

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Exports
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Exports recursive
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Description
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(define <variable> <expression>)
(define (<variable> <formals>) <body>)
Variable definitions

A variable definition binds one or more identifiers and specifies an initial value for each of them. The simplest kind of variable definition takes one of the following forms:

<Formals> are either a sequence of zero or more variables, or a sequence of one or more variables followed by a space-delimited period and another variable (as in a lambda expression). This form is equivalent to

(define <variable>
  (lambda (<formals>) <body>))

<Formal> is a single variable. This form is equivalent to

(define <variable>
  (lambda <formal> <body>))
Top level definitions

At the outermost level of a program, a definition

(define <variable> <expression>)

has essentially the same effect as the assignment expression

(set! <variable> <expression>)

if <variable> is bound to a non-syntax value. However, if <variable> is not bound, or is a syntactic keyword, then the definition will bind <variable> to a new location before performing the assignment, whereas it would be an error to perform a set! on an unbound variable.

(define add3
  (lambda (x) (+ x 3)))
(add3 3)                            ===>  6
(define first car)
(first '(1 2))                      ===>  1

The text herein was sourced and adapted as described in the "R7RS attribution of various text snippets" appendix.

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