unless -- r7rs Definition

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Kind

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syntax;

Implemented by

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• unless (from vonuvoli);

Syntax signature

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Syntax keywords:

• condition: expression;
• then-expression: expression;

Syntax variants:

• (_ condition then-expression |...|)

Exports

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• scheme:base -- (scheme base);

Exports recursive

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• scheme -- (scheme);

Description

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(unless <test> <expression_1> <expression_2> ...)

Syntax: The <test> is an expression.

Semantics: The test is evaluated, and if it evaluates to #f, the expressions are evaluated in order. The result of the unless expression is unspecified.

(unless (= 1 1.0)
  (display "1")
  (display "2"))  ===>  #unspecified
           ; and prints nothing

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