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log10, log10f, log10l - 常用对数,以 10 为底的对数

函数原型:

函数原型 C90 C99 C++98 C++11
double log10(double x);
float log10f(float x);      
long double log10l(long double x);      
float log10(float x);    
long double log10(long double x);    

头文件:

#include <cmath>

命名空间:

std

参数:

x:浮点数,定义域范围为 [0, +Infinity]

返回值:

x 的常用对数值,x 的以 10 为底的对数值,值域范围为 [-Infinity, +Infinity]
NAN:定义域错误,此时全局变量 errno 的值为 EDOM

例子:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  Memo1->Lines->Add(L"log10(  0   ) = " + FloatToStr(std::log10( 0.0     )));
  Memo1->Lines->Add(L"log10( 3e-69) = " + FloatToStr(std::log10( 3e-69   )));
  Memo1->Lines->Add(L"log10(  0.01) = " + FloatToStr(std::log10( 0.01    )));
  Memo1->Lines->Add(L"log10(  1   ) = " + FloatToStr(std::log10( 1.0     )));
  Memo1->Lines->Add(L"log10( 12.34) = " + FloatToStr(std::log10(12.34    )));
  Memo1->Lines->Add(L"log10(100   ) = " + FloatToStr(std::log10(100.0    )));
  Memo1->Lines->Add(L"log10(5.6e98) = " + FloatToStr(std::log10(5.6e98   )));
  Memo1->Lines->Add(L"log10( +∞   ) = " + FloatToStr(std::log10( Infinity)));
  Memo1->Lines->Add(L"log10( -2   ) = " + FloatToStr(std::log10(-2.0     )));
  Memo1->Lines->Add(L"log10( -∞   ) = " + FloatToStr(std::log10(-Infinity)));
}

兼容性:

函数 \ C++ Builder 编译器 bcc32 clang32 clang64
log10
log10f   版本 ≥ 10.2 Tokyo Update 1
log10l

相关链接:

expexp2expm1loglog1plog2powpow10sqrt_matherr浮点数异常处理

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