std::strtof
std::strtof, std::strtod, std::strtold
| Defined in header | | |
|---|---|---|
| float strtof( const char* str, char** str_end | | (since C++11) |
| double strtod( const char* str, char** str_end | | |
| long double strtold( const char* str, char** str_end | | (since C++11) |
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:
The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is NULL, it is ignored.
Parameters
| str | - | pointer to the null-terminated byte string to be interpreted |
|---|---|---|
| str_end | - | pointer to a pointer to character. |
Return value
Floating point value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, range error occurs and HUGE_VAL, HUGE_VALF or HUGE_VALL is returned. If no conversion can be performed, 0 is returned and *str_end is set to str.
Example
#include <iostream>
#include <string>
#include <cerrno>
#include <cstdlib>
int main()
{
const char* p = "111.11 -2.22 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz";
char* end;
std::cout << "Parsing \"" << p << "\":\n";
for (double f = std::strtod(p, &end p != end; f = std::strtod(p, &end))
{
std::cout << "'" << std::string(p, end-p) << "' -> ";
p = end;
if (errno == ERANGE){
std::cout << "range error, got ";
errno = 0;
}
std::cout << f << '\n';
}
}
Output:
Parsing "111.11 -2.22 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz":
'111.11' -> 111.11
' -2.22' -> -2.22
' 0X1.BC70A3D70A3D7P+6' -> 111.11
' 1.18973e+4932' -> range error, got inf
See also
| atof | converts a byte string to a floating point value (function) |
|---|---|
| wcstofwcstodwcstold | converts a wide string to a floating point value (function) |
| from_chars (C++17) | converts a character sequence to an integer or floating-point value (function) |
| C documentation for strtof, strtod, strtold |
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