std::wcstof, std::wcstod, std::wcstold - cppreference.com (original) (raw)
| Defined in header | | | | -------------------------------------------------------------------------- | | ------------- | | float wcstof( const wchar_t* str, wchar_t** str_end ); | | (since C++11) | | double wcstod( const wchar_t* str, wchar_t** str_end ); | | | | long double wcstold( const wchar_t* str, wchar_t** str_end ); | | (since C++11) |
Interprets a floating point value in a wide string pointed to by str.
Function discards any whitespace characters (as determined by std::iswspace) 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)
**e**or**E**followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10)
| hexadecimal floating-point expression. It consists of the following parts: (optional) plus or minus sign 0x or 0X nonempty sequence of hexadecimal digits optionally containing a decimal-point character (as determined by the current C locale) (defines significand) (optional) p or P followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 2) infinity expression. It consists of the following parts: (optional) plus or minus sign INF or INFINITY ignoring case not-a-number expression. It consists of the following parts: (optional) plus or minus sign NAN or NAN(char_sequence ) ignoring case of the NAN part. char_sequence can only contain digits, Latin letters, and underscores. The result is a quiet NaN floating-point value. | (since C++11) |
|---|
- any other expression that may be accepted by the currently installed C locale.
The functions sets the pointer pointed to by str_end to point to the wide character past the last character interpreted. If str_end is a null pointer, it is ignored.
[edit] Parameters
| str | - | pointer to the null-terminated wide string to be interpreted |
|---|---|---|
| str_end | - | pointer to a pointer to a wide character |
[edit] 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.
[edit] Example
#include #include #include #include #include int main() { const wchar_t* p = L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz"; wchar_t* end; std::wcout << "Parsing L"" << p << "":\n"; for (double f = std::wcstod(p, &end); p != end; f = std::wcstod(p, &end)) { std::wcout << " '" << std::wstring(p, end-p) << "' -> "; p = end; if (errno == ERANGE) { std::wcout << "range error, got "; errno = 0; } std::wcout << f << '\n'; } if (std::setlocale(LC_NUMERIC, "de_DE.utf8")) { std::wcout << L"With de_DE.utf8 locale:\n"; std::wcout << L" '123.45' -> " << std::wcstod(L"123.45", 0) << L'\n'; std::wcout << L" '123,45' -> " << std::wcstod(L"123,45", 0) << L'\n'; } }
Output:
Parsing L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz": '111.11' -> 111.11 ' -2.22' -> -2.22 ' 0X1.BC70A3D70A3D7P+6' -> 111.11 ' -Inf' -> -inf ' 1.18973e+4932' -> range error, got inf With de_DE.utf8 locale: '123.45' -> 123 '123,45' -> 123.45