number? -- r7rs Definition

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Kind

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type-predicate;

Extended by

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• number? (from vonuvoli);

Procedure signature

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Procedure variants:

• ((integer) -> (true))
  • input: a value of type integer;
  • output: a value of type true;
• ((rational) -> (true))
  • input: a value of type rational;
  • output: a value of type true;
• ((real) -> (true))
  • input: a value of type real;
  • output: a value of type true;
• ((complex) -> (true))
  • input: a value of type complex;
  • output: a value of type true;
• ((number) -> (true))
  • input: a value of type number;
  • output: a value of type true;
• ((any) -> (false))
  • input: a value of type any;
  • output: a value of type false;

Exports

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• scheme:base -- (scheme base);

Exports recursive

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• scheme -- (scheme);

Description

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(number? obj)
(complex? obj)
(real? obj)
(rational? obj)
(integer? obj)

These numerical type predicates can be applied to any kind of argument, including non-numbers. They return #t if the object is of the named type, and otherwise they return #f. In general, if a type predicate is true of a number then all higher type predicates are also true of that number. Consequently, if a type predicate is false of a number, then all lower type predicates are also false of that number.

If z is a complex number, then (real? z) is true if and only if (zero? (imag-part z)) is true. If x is an inexact real number, then (integer? x) is true if and only if (= x (round x)).

The numbers +inf.0, -inf.0, and +nan.0 are real but not rational.

(complex? 3+4i)         ===>  #t
(complex? 3)            ===>  #t
(real? 3)               ===>  #t
(real? -2.5+0i)         ===>  #t
(real? -2.5+0.0i)       ===>  #f
(real? #e1e10)          ===>  #t
(real? +inf.0)          ===>  #t
(real? +nan.0)          ===>  #t
(rational? -inf.0)      ===>  #f
(rational? 3.5)         ===>  #t
(rational? 6/10)        ===>  #t
(rational? 6/3)         ===>  #t
(integer? 3+0i)         ===>  #t
(integer? 3.0)          ===>  #t
(integer? 8/4)          ===>  #t

Note: The behavior of these type predicates on inexact numbers is unreliable, since any inaccuracy might affect the result.

Note: In many implementations the complex? procedure will be the same as number?, but unusual implementations may represent some irrational numbers exactly or may extend the number system to support some kind of non-complex numbers.

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

Referenced-types

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• integer;
• true;
• rational;
• real;
• complex;
• number;
• any;
• false;