The header<tgmath.h> includes the headers<math.h> and<complex.h> and defines severaltype-generic macros that determine which real or, when applicable, complex function to call based on the types of the arguments.

For each macro, the parameters whose corresponding real type in the unsuffixed<math.h> function isdouble are known asgeneric parameters (for example, both parameters ofpow are generic parameters, but only the first parameter ofscalbn is a generic parameter).

When a<tgmath.h>'s macro is used the types of the arguments passed to the generic parameters determine which function is selected by the macro as described below. If the types of the arguments are notcompatible with the parameter types of the selected function, the behavior is undefined (e.g. if a complex argument is passed into a real-only<tgmath.h>'s macro:floatcomplex fc;ceil(fc); ordoublecomplex dc;double d;fmax(dc, d); are examples of undefined behavior).

Note: type-generic macros were implemented in implementation-defined manner in C99, but C11 keyword_Generic makes it possible to implement these macros in portable manner.

[edit]Complex/real type-generic macros

For all functions that have both real and complex counterparts, a type-generic macroXXX exists, which calls either of:

• real function:

• float variantXXXf
• double variantXXX
• longdouble variantXXXl

• complex function:

• float variantcXXXf
• double variantcXXX
• longdouble variantcXXXl

An exception to the above rule is thefabs macro (see the table below).

The function to call is determined as follows:

• If any of the arguments for the generic parameters is imaginary, the behavior is specified on each function reference page individually (in particular,sin,cos,tan,cosh,sinh,tanh,asin,atan,asinh, andatanh callreal functions, the return types ofsin,tan,sinh,tanh,asin,atan,asinh, andatanh are imaginary, and the return types ofcos andcosh are real).
• If any of the arguments for the generic parameters is complex, then the complex function is called, otherwise the real function is called.
• If any of the arguments for the generic parameters islongdouble, then thelongdouble variant is called. Otherwise, if any of the parameters isdouble or integer, then thedouble variant is called. Otherwise,float variant is called.

The type-generic macros are as follows:

[edit]Real-only functions

For all functions that do not have complex counterparts, with the exception ofmodf, a type-generic macroXXX exists, which calls either of the variants of a real function:

• float variantXXXf
• double variantXXX
• longdouble variantXXXl

The function to call is determined as follows:

• If any of the arguments for the generic parameters islongdouble, then thelongdouble variant is called. Otherwise, if any of the arguments for the generic parameters isdouble, then thedouble variant is called. Otherwise,float variant is called.

[edit]Complex-only functions

For all complex number functions that do not have real counterparts, a type-generic macrocXXX exists, which calls either of the variants of a complex function:

• floatcomplex variantcXXXf
• doublecomplex variantcXXX
• longdoublecomplex variantcXXXl

The function to call is determined as follows:

• If any of the arguments for the generic parameters is real, complex, or imaginary, then the appropriate complex function is called.

[edit]Example

#include <stdio.h>#include <tgmath.h> int main(void){int i=2;printf("sqrt(2) = %f\n",sqrt(i));// argument type is int, calls sqrt float f=0.5;printf("sin(0.5f) = %f\n",sin(f));// argument type is float, calls sinf floatcomplex dc=1+0.5*I;floatcomplex z=sqrt(dc);// argument type is float complex, calls csqrtfprintf("sqrt(1 + 0.5i) = %f+%fi\n",creal(z),// argument type is float complex, calls crealfcimag(z));// argument type is float complex, calls cimagf}

sqrt(2) = 1.414214sin(0.5f) = 0.479426sqrt(1 + 0.5i) = 1.029086+0.242934i

[edit]References

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