C Standard Library<tgmath.h>

<tgmath.h>is a header file in the C standard library, providingType-generic math functions（Type-Generic Math Functions）。

<tgmath.h>The library was introduced in the C99 standard, allowing developers to use unified function names to call different types of mathematical functions (such asfloat、doubleandlong double), without needing to explicitly specify the specific type of the function.

<tgmath.h>The main purpose is:

  • It simplifies the use of mathematical functions, avoiding the need to define separate functions for different types (such asfloat、double、long double) explicitly call different functions (e.g.sinf、sin、sinl）。

  • Improve code readability and maintainability.

  • Mathematical functions supporting complex types.

1、Type-generic macros

<tgmath.h>It defines a set of type-generic macros that automatically select the correct mathematical function based on the type of the argument. For example:

  • sin(x): ifxYesfloat, then callsinf(x); ifxYesdouble, then callsin(x); ifxYeslong double, then callsinl(x)。

  • sqrt(x): ifxYesfloat, then callsqrtf(x); ifxYesdouble, then callsqrt(x); ifxYeslong double, then callsqrtl(x)。

These macros support arguments of the following types:

  • Real types:float、double、long double。

  • Complex types:float complex、double complex、long double complex。

2、Supported functions

<tgmath.h>The following type-generic math functions are supported:

Basic mathematical functions

Function Description
sin Sine function
cos Cosine function
tan Tangent function
asin Arcsine function
acos Arccosine function
atan Arctangent function
atan2 Two-argument arctangent function
sinh Hyperbolic sine function
cosh Hyperbolic cosine function
tanh Hyperbolic tangent function
asinh Inverse hyperbolic sine function
acosh Inverse hyperbolic cosine function
atanh Inverse hyperbolic tangent function

Exponential and logarithmic functions

Function Description
exp Exponential function
log Natural logarithm function
log10 Common logarithm function
pow power function

Other functions

Function Description
sqrt square root function
fabs Absolute value function
ceil Ceiling function
floor Floor function
fmod Floating-point remainder function

3、Example

The following is an example using<tgmath.h>is an example that demonstrates how to use type-generic mathematical functions:

Example

#include <stdio.h>
#include <tgmath.h>

int main() {
    // real types
    float f = 1.5f;
    double d = 2.5;
    long double ld = 3.5L;

    // use type-generic functions
    printf("sin(f) = %f\n", sin(f));       // call sinf
    printf("sin(d) = %f\n", sin(d));       // call sin
    printf("sin(ld) = %Lf\n", sin(ld));    // call sinl

    // complex types
    double complex z = 1.0 + 2.0 * I;

    // use type-generic functions
    double complex sqrt_z = sqrt(z);
    printf("sqrt(z) = %f + %fi\n", creal(sqrt_z), cimag(sqrt_z));

    return 0;
}

Output result：

sin(f) = 0.997495
sin(d) = 0.598472
sin(ld) = 0.350783
sqrt(z) = 1.272020 + 0.786151i

4、Notes

  • <tgmath.h>It is only available in C99 and later versions.

  • Type-generic macros automatically select the correct function based on the type of the argument, so the type of the argument must be clear.

  • If the argument type is ambiguous (e.g., an integer constant), the compiler may choose the defaultdoubleversion.

  • Functions for complex types need to include<complex.h>Header file.

5、Implementation principle

<tgmath.h>The implementation relies on C's generic selection mechanism (_Generickeyword). For example,sinThe macro definition may be as follows:

#define sin(x) _Generic((x), \
    float: sinf,             \
    double: sin,             \
    long double: sinl        \
)(x)

_Generickeyword based onxof the type to select the correct function.

<tgmath.h>It provides type-generic mathematical functions, simplifying calls for different numeric types (such asfloat、double、long doubleand complex types). It is an important feature in the C99 standard, especially suitable for scientific computing and engineering applications that need to handle multiple numeric types. By using<tgmath.h>, developers can write more concise and more generic code.

other extensions