string->number -- r7rs Definition

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Kind

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converter;

Implemented by

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• string->number (from vonuvoli);

Procedure signature

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Procedure variants:

• ((string-empty) -> (false))
  • input: a value of type string-empty;
  • output: a value of type false;
• ((string-not-empty) -> (number-or-false))
  • input: a value of type string-not-empty;
  • output: a value of type number-or-false;
• ((string-empty number-radix) -> (false))
  • inputs:
    • a value of type string-empty;
    • a value of type number-radix;
  • output: a value of type false;
• ((string-not-empty number-radix) -> (number-or-false))
  • inputs:
    • a value of type string-not-empty;
    • a value of type number-radix;
  • output: a value of type number-or-false;

Exports

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• scheme:base -- (scheme base);

Exports recursive

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• scheme -- (scheme);

Description

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(string->number string)
(string->number string radix)

Returns a number of the maximally precise representation expressed by the given string.

Domain: It is an error if radix is not 2, 8, 10, or 16.

If supplied, radix is a default radix that will be overridden if an explicit radix prefix is present in string (e.g. "#o177"). If radix is not supplied, then the default radix is 10. If string is not a syntactically valid notation for a number, or would result in a number that the implementation cannot represent, then string->number returns #f. An error is never signaled due to the content of string.

(string->number "100")        ===>  100
(string->number "100" 16)     ===>  256
(string->number "1e2")        ===>  100.0

Note: The domain of string->number may be restricted by implementations in the following ways. If all numbers supported by an implementation are real, then string->number is permitted to return #f whenever string uses the polar or rectangular notations for complex numbers. If all numbers are integers, then string->number may return #f whenever the fractional notation is used. If all numbers are exact, then string->number may return #f whenever an exponent marker or explicit exactness prefix is used. If all inexact numbers are integers, then string->number may return #f whenever a decimal point is used.

Note: The rules used by a particular implementation for string->number must also be applied to read and to the routine that reads programs, in order to maintain consistency between internal numeric processing, I/O, and the processing of programs. As a consequence, the R5RS permission to return #f when string has an explicit radix prefix has been withdrawn.

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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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• string-empty;
• false;
• string-not-empty;
• number-or-false;
• number-radix;