std::log,st...f,std::logl(3)

okay bestie, welcome to the std::log,st...f,std::logl(3) page from the C++ Standard Libary manual ✨ this one is all about the natural log function and its overload besties — no cap, it’s lowkey iconic.

💖 NAME 💖

std::log,std::logf,std::logl — std::log,std::logf,std::logl 🫶

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🌈 SYNOPSIS 🌈

bestie, here’s the whole overload situation — yes, all of it, don’t skip, this is the main character energy of the page:

Defined in header <cmath>

float       log ( float num );

double      log ( double num );                            (until C++23)

long double log ( long double num );
/* floating-point-type */                                  (since C++23)
            log ( /* floating-point-type */ num );         (constexpr since C++26)

float       logf( float num );                     (1) (2) (since C++11)
                                                                   (constexpr since C++26)

long double logl( long double num );                   (3) (since C++11)
                                                                   (constexpr since C++26)

Additional overloads (since C++11)
Defined in header <cmath>

template< class Integer >                              (A) (constexpr since C++26)
double      log ( Integer num );

• 1-3) Computes the natural (base e) logarithm of num. 💅
• The library provides overloads of std::log for all cv-unqualified floating-point types as the type of the parameter. (since C++23) ✨
• A) Additional overloads are provided for all integer types, which are treated as double. (since C++11) 🎀

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🎀 PARAMETERS 🎀

• num — floating-point or integer value 🫶

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🔥 RETURN VALUE 🔥

If no errors occur, the natural (base-e) logarithm of num (that’s ln(num) or log e(num)) is returned. slay. 💖

If a domain error occurs, an implementation-defined value is returned (NaN where supported). 😭

If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned. 💀

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💀 ERROR HANDLING 💀

Errors are reported as specified in math_errhandling.

Domain error occurs if num is less than zero.

Pole error may occur if num is zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559), here’s the tea:

• If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
• If the argument is 1, +0 is returned.
• If the argument is negative, NaN is returned and FE_INVALID is raised.
• If the argument is +∞, +∞ is returned.
• If the argument is NaN, NaN is returned.

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📝 NOTES 📝

The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::log(num) has the same effect as std::log(static_cast<double>(num)). periodt. 💅

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🧪 EXAMPLE 🧪

okay this is the part where you actually run it — copy-paste era:

// Run this code

#include <cerrno>
#include <cfenv>
#include <cmath>
#include <cstring>
#include <iostream>
// #pragma STDC FENV_ACCESS ON

int main()
{
    std::cout << "log(1) = " << std::log(1) << '\n'
              << "base-5 logarithm of 125 = " << std::log(125) /
                 std::log(5) << '\n';

    // special values
    std::cout << "log(1) = " << std::log(1) << '\n'
              << "log(+Inf) = " << std::log(INFINITY) << '\n';

    // error handling
    errno = 0;
    std::feclearexcept(FE_ALL_EXCEPT);

    std::cout << "log(0) = " << std::log(0) << '\n';

    if (errno == ERANGE)
        std::cout << "    errno == ERANGE: " << std::strerror(errno) <<
                     '\n';
    if (std::fetestexcept(FE_DIVBYZERO))
        std::cout << "    FE_DIVBYZERO raised\n";
}

💻 Possible output 💻

log(1) = 0
base-5 logarithm of 125 = 3
log(1) = 0
log(+Inf) = inf
log(0) = -inf
    errno == ERANGE: Numerical result out of range
    FE_DIVBYZERO raised

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👀 SEE ALSO 👀

• log10, log10f, log10l — computes common (base 10) logarithm; log10l is log[10](x). (C++11) (function) (C++11)
• log2, log2f, log2l — base 2 logarithm of the given number; log2l is log[2](x). (C++11) (function) (C++11) (C++11)
• log1p, log1pf, log1pl — natural logarithm (to base e) of 1 plus the given number; log1pl is ln(1+x). (C++11) (function) (C++11) (C++11)
• exp, expf, expl — returns e raised to the given power (e^x). (function) (C++11) (C++11)
• log(std::complex) — complex natural logarithm with the branch cuts along the negative real axis. (function template)
• log(std::valarray) — applies the function std::log to each element of valarray. (function template)
• C documentation for log

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💖 that’s the whole page, bestie! source: http://cppreference.com, version/date: 2024.06.10, page: std::log,st...f,std::logl(3) — mwah 🎀✨