📜  C / C++中的wcstod()函数

📅  最后修改于: 2021-05-30 16:26:41             🧑  作者: Mango

wcstod()函数将宽字符串转换为double 。此函数将宽字符串的内容解释为浮点数。如果endString不是空指针,则该函数还会将endString的值设置为指向数字后的第一个字符。

句法:

double wcstod( const wchar_t* str, wchar_t** str_end )

参数:该函数接受两个强制性参数,如下所述:

  • 字符串:指定以浮点数表示形式开头的字符串
  • endString:指定指向宽字符的指针

返回值:该函数返回两个值,如下所示:

  • 成功后,函数将转换后的浮点数作为double类型的值返回。
  • 如果无法执行有效的转换,则返回0.0。
  • 如果正确的值超出该类型可表示的值的范围,则返回正数或负数HUGE_VAL,并将errno设置为ERANGE。
  • 如果正确的值将导致下溢,则该函数将返回一个其大小不大于最小归一化正数的值(在这种情况下,某些库实现也可能会将errno设置为ERANGE)。

下面的程序说明了上述函数:
程序1:

// C++ program to illustrate
// wcstod() function
  
#include 
using namespace std;
  
int main()
{
    // initialize the wide string
    // beginning with the floating point number
    wchar_t string[] = L"95.6Geek";
  
    // Pointer to a pointer to a wide character
    wchar_t* endString;
  
    // Convert wide string to double
    double value = wcstod(string, &endString);
  
    // print the string, starting double value
    // and its endstring
    wcout << L"String -> " << string << "\n";
    wcout << L"Double value -> " << value << "\n";
    wcout << L"End String is : " << endString << "\n";
  
    return 0;
}
输出:
String -> 95.6Geek
Double value -> 95.6
End String is : Geek

程序2:

// C++ program to illustrate
// wcstod() function
// with no endString characters
#include 
using namespace std;
  
int main()
{
    // initialize the wide string
    // beginning with the floating point number
    wchar_t string[] = L"10.6464";
  
    // Pointer to a pointer to a wide character
    wchar_t* endString;
  
    // Convert wide string to double
    double value = wcstod(string, &endString);
  
    // print the string, starting double value
    // and its endstring
    wcout << L"String -> " << string << "\n";
    wcout << L"Double value -> " << value << "\n";
    wcout << L"End String is : " << endString << "\n";
  
    return 0;
}
输出:
String -> 10.6464
Double value -> 10.6464
End String is :

程序3:

// C++ program to illustrate
// wcstod() function
// with whitespace present at the beginning
#include 
using namespace std;
  
int main()
{
    // initialize the wide string
    // beginning with the floating point number
    wchar_t string[] = L"            99.999Geek";
  
    // Pointer to a pointer to a wide character
    wchar_t* endString;
  
    // Convert wide string to double
    double value = wcstod(string, &endString);
  
    // print the string, starting double value
    // and its endstring
    wcout << L"String -> " << string << "\n";
    wcout << L"Double value -> " << value << "\n";
    wcout << L"End String is : " << endString << "\n";
  
    return 0;
}
输出:
String ->             99.999Geek
Double value -> 99.999
End String is : Geek
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