Difference between revisions of "cpp/string/byte/atof"
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}} | }} | ||
| − | Interprets a floating point value in a byte string pointed to by {{ | + | Interprets a floating point value in a byte string pointed to by {{c|str}}. |
{{cpp/string/cvt str2float}} | {{cpp/string/cvt str2float}} | ||
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===Return value=== | ===Return value=== | ||
| − | {{c|double}} value corresponding to the contents of {{ | + | {{c|double}} value corresponding to the contents of {{c|str}} on success. If the converted value falls out of range of the return type, the return value is undefined. If no conversion can be performed, {{c|0.0}} is returned. |
===Example=== | ===Example=== | ||
{{example | {{example | ||
| − | |||
|code= | |code= | ||
#include <cstdlib> | #include <cstdlib> | ||
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{ | { | ||
std::cout << std::atof("0.0000000123") << '\n' | std::cout << std::atof("0.0000000123") << '\n' | ||
| − | << std::atof("0.012") | + | << std::atof("0.012") << '\n' |
| − | << std::atof("15e16") | + | << std::atof("15e16") << '\n' |
| − | << std::atof("-0x1afp-2") | + | << std::atof("-0x1afp-2") << '\n' |
| − | << std::atof("inF") | + | << std::atof("inF") << '\n' |
| − | << std::atof("Nan") | + | << std::atof("Nan") << '\n' |
| − | << std::atof("invalid") | + | << std::atof("invalid") << '\n'; |
} | } | ||
|output= | |output= | ||
Latest revision as of 08:28, 5 June 2023
| Defined in header <cstdlib>
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| double atof( const char* str ); |
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Interprets a floating point value in a byte string pointed to by str.
Function discards any whitespace characters (as determined by std::isspace) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating-point representation and converts them to a floating-point value. The valid floating-point value can be one of the following:
- decimal floating-point expression. It consists of the following parts:
- (optional) plus or minus sign
- nonempty sequence of decimal digits optionally containing decimal-point character (as determined by the current C locale) (defines significand)
- (optional)
eorEfollowed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10)
|
(since C++11) |
- any other expression that may be accepted by the currently installed C locale
Contents |
[edit] Parameters
| str | - | pointer to the null-terminated byte string to be interpreted |
[edit] Return value
double value corresponding to the contents of str on success. If the converted value falls out of range of the return type, the return value is undefined. If no conversion can be performed, 0.0 is returned.
[edit] Example
Run this code
#include <cstdlib> #include <iostream> int main() { std::cout << std::atof("0.0000000123") << '\n' << std::atof("0.012") << '\n' << std::atof("15e16") << '\n' << std::atof("-0x1afp-2") << '\n' << std::atof("inF") << '\n' << std::atof("Nan") << '\n' << std::atof("invalid") << '\n'; }
Output:
1.23e-08 0.012 1.5e+17 -107.75 inf nan 0
[edit] See also
| (C++11)(C++11)(C++11) |
converts a string to a floating point value (function) |
| converts a byte string to a floating-point value (function) | |
| (C++17) |
converts a character sequence to an integer or floating-point value (function) |
| (C++11) |
converts a byte string to an integer value (function) |
| C documentation for atof
| |
