C++ logb()用法及代碼示例

logb()是C++ STL中的內置函數，它使用FLT_RADIX作為對數的底數，返回| x |的對數。通常，FLT_RADIX的值為2，因此logb()等效於log2()(僅適用於正值)。

用法：

logb(val)

參數：該函數接受單個強製參數val，該參數指定要計算其logb()的val。數據類型可以是double，float，long double或int。

返回類型：該函數返回| x |的對數。

以下示例程序旨在說明上述函數：

程序1：

// C++ program to illustrate 
// to implement logb() function 
// when data-type is integer 
#include <cmath> 
#include <iostream> 
using namespace std; 
int main() 
{ 
    double result; 
    int x = -10; 
  
    result = logb(x); 
    cout << "logb(" << x << ") = "
         << "log(|" << x << "|) = " << result << endl; 
  
    x = 10; 
  
    result = logb(x); 
    cout << "logb(" << x << ") = "
         << "log(|" << x << "|) = " << result << endl; 
  
    return 0; 
}

輸出：

logb(-10) = log(|-10|) = 3
logb(10) = log(|10|) = 3

程序2：

// C++ program to illustrate 
// to implement logb() function 
// when data-type is double 
#include <cmath> 
#include <iostream> 
  
using namespace std; 
  
int main() 
{ 
    double x = 70.56, result; 
  
    result = logb(x); 
    cout << "logb(" << x << ") = "
         << "log(|" << x << "|) = " << result << endl; 
  
    x = 17.6; 
  
    result = logb(x); 
    cout << "logb(" << x << ") = "
         << "log(|" << x << "|) = " << result << endl; 
  
    return 0; 
}

輸出：

logb(70.56) = log(|70.56|) = 6
logb(17.6) = log(|17.6|) = 4

程序3：

// C++ program to illustrate 
// to implement logb() function 
// when input is 0 
#include <cmath> 
#include <iostream> 
  
using namespace std; 
  
int main() 
{ 
    double result; 
    int x = 0; 
  
    result = logb(x); 
    cout << "logb(" << x << ") = "
         << "log(|" << x << "|) = " << result << endl; 
  
    return 0; 
}

輸出：

logb(0) = log(|0|) = -inf

相關用法

注：本文由純淨天空篩選整理自IshwarGupta大神的英文原創作品 logb() function in C++ STL。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。