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Difference between revisions of "cpp/string/wide/wcstof"

From cppreference.com
< cpp‎ | string‎ | wide
(port example, seealso)
m ({{c}}, headers sorted, fmt, langlinks)
 
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{{cpp/title| wcstof | wcstod | wcstold}}
+
{{cpp/title|wcstof|wcstod|wcstold}}
 
{{cpp/string/wide/navbar}}
 
{{cpp/string/wide/navbar}}
 
{{dcl begin}}
 
{{dcl begin}}
−
{{dcl header | cwchar}}
+
{{dcl header|cwchar}}
−
{{dcl | since=c++11 |
+
{{dcl|since=c++11|
 
float      wcstof( const wchar_t* str, wchar_t** str_end );           
 
float      wcstof( const wchar_t* str, wchar_t** str_end );           
 
}}
 
}}
−
{{dcl |  
+
{{dcl|  
 
double      wcstod( const wchar_t* str, wchar_t** str_end );
 
double      wcstod( const wchar_t* str, wchar_t** str_end );
 
}}
 
}}
−
{{dcl | since=c++11 |
+
{{dcl|since=c++11|
 
long double wcstold( const wchar_t* str, wchar_t** str_end );
 
long double wcstold( const wchar_t* str, wchar_t** str_end );
 
}}
 
}}
 
{{dcl end}}
 
{{dcl end}}
  
−
Interprets a floating point value in a wide string pointed to by {{tt|str}}.
+
Interprets a floating point value in a wide string pointed to by {{c|str}}.
  
 
{{cpp/string/cvt str2float|wide}}
 
{{cpp/string/cvt str2float|wide}}
  
−
The functions sets the pointer pointed to by {{tt|str_end}} to point to the wide character past the last character interpreted. If {{tt|str_end}} is {{lc|NULL}}, it is ignored.
+
The functions sets the pointer pointed to by {{c|str_end}} to point to the wide character past the last character interpreted. If {{c|str_end}} is a null pointer, it is ignored.
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
−
{{par | str | pointer to the null-terminated wide string to be interpreted}}
+
{{par|str|pointer to the null-terminated wide string to be interpreted}}
−
{{par | str_end | pointer to a pointer to a wide character.}}
+
{{par|str_end|pointer to a pointer to a wide character}}
 
{{par end}}
 
{{par end}}
  
 
===Return value===
 
===Return value===
−
Floating point value corresponding to the contents of {{tt|str}} on success. If the converted value falls out of range of corresponding return type, range error occurs and {{lc|HUGE_VAL}}, {{lc|HUGE_VALF}} or {{lc|HUGE_VALL}} is returned. If no conversion can be performed, {{c|0}} is returned.
+
Floating point value corresponding to the contents of {{c|str}} on success. If the converted value falls out of range of corresponding return type, range error occurs and {{lc|HUGE_VAL}}, {{lc|HUGE_VALF}} or {{lc|HUGE_VALL}} is returned. If no conversion can be performed, {{c|0}} is returned.
  
 
===Example===
 
===Example===
 
{{example
 
{{example
−
|
+
|code=
−
| code=
+
#include <cerrno>
 +
#include <clocale>
 +
#include <cwchar>
 
#include <iostream>
 
#include <iostream>
 
#include <string>
 
#include <string>
−
#include <cerrno>
 
−
#include <cstdlib>
 
  
 
int main()
 
int main()
 
{
 
{
−
     const wchar_t* p = L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz";
+
     const wchar_t* p = L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz";
 
     wchar_t* end;
 
     wchar_t* end;
 
     std::wcout << "Parsing L\"" << p << "\":\n";
 
     std::wcout << "Parsing L\"" << p << "\":\n";
 
     for (double f = std::wcstod(p, &end); p != end; f = std::wcstod(p, &end))
 
     for (double f = std::wcstod(p, &end); p != end; f = std::wcstod(p, &end))
 
     {
 
     {
−
         std::wcout << "'" << std::wstring(p, end-p) << "' -> ";
+
         std::wcout << " '" << std::wstring(p, end-p) << "' -> ";
 
         p = end;
 
         p = end;
−
         if (errno == ERANGE){
+
         if (errno == ERANGE)
 +
        {
 
             std::wcout << "range error, got ";
 
             std::wcout << "range error, got ";
 
             errno = 0;
 
             errno = 0;
 
         }
 
         }
 
         std::wcout << f << '\n';
 
         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=
+
|output=
−
Parsing L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz":
+
Parsing L"111.11 -2.22 0X1.BC70A3D70A3D7P+6 -Inf 1.18973e+4932zzz":
−
'111.11' -> 111.11
+
  '111.11' -> 111.11
−
' -2.22' -> -2.22
+
  ' -2.22' -> -2.22
−
' 0X1.BC70A3D70A3D7P+6' -> 111.11
+
  ' 0X1.BC70A3D70A3D7P+6' -> 111.11
−
' 1.18973e+4932' -> range error, got inf
+
  ' -Inf' -> -inf
 +
  ' 1.18973e+4932' -> range error, got inf
 +
With de_DE.utf8 locale:
 +
  '123.45' -> 123
 +
  '123,45' -> 123.45
 
}}
 
}}
  
 
===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/string/byte/dsc strtof}}
+
{{dsc inc|cpp/string/byte/dsc strtof}}
−
{{dsc see c | c/string/wide/wcstof}}
+
{{dsc see c|c/string/wide/wcstof}}
 
{{dsc end}}
 
{{dsc end}}
  
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[[de:cpp/string/wide/wcstof]]
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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[[es:cpp/string/wide/wcstof]]
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−
[[fr:cpp/string/wide/wcstof]]
+
−
[[it:cpp/string/wide/wcstof]]
+
−
[[ja:cpp/string/wide/wcstof]]
+
−
[[pt:cpp/string/wide/wcstof]]
+
−
[[ru:cpp/string/wide/wcstof]]
+
−
[[zh:cpp/string/wide/wcstof]]
+

Latest revision as of 10:26, 10 June 2023

 
C++
 
Strings library
 
Null-terminated wide strings
 
Defined in header <cwchar>
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.

Contents

[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

Run this code
#include <cerrno>
#include <clocale>
#include <cwchar>
#include <iostream>
#include <string>
 
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

[edit] See also

 converts a byte string to a floating-point value
(function) [edit]
C documentation for wcstof
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