39. Type-generic math <tgmath.h>ΒΆ

The header <tgmath.h> includes the headers <math.h> and <complex.h> and defines several type-generic macros.

Of the <math.h> and <complex.h> functions without an f (float) or l (long double) suffix, several have one or more parameters whose corresponding real type is double. For each such function, except modf, there is a corresponding type-generic macro. 1 The parameters whose corresponding real type is double in the function synopsis are generic parameters. Use of the macro invokes a function whose corresponding real type and type domain are determined by the arguments for the generic parameters. 2

1

Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to make available the corresponding ordinary function.

2

If the type of the argument is not compatible with the type of the parameter for the selected function, the behavior is undefined.

Use of the macro invokes a function whose generic parameters have the corresponding real type determined as follows:

  • First, if any argument for generic parameters has type long double, the type determined is long double.

  • Otherwise, if any argument for generic parameters has type double or is of integer type, the type determined is double.

  • Otherwise, the type determined is float.

For each unsuffixed function in <math.h> for which there is a function in <complex.h> with the same name except for a c prefix, the corresponding type-generic macro (for both functions) has the same name as the function in <math.h>. The corresponding type-generic macro for fabs and cabs is fabs.

<math.h> functions

<complex.h> functions

type-generic funcions

acos

cacos

acos

asin

casin

asin

atan

catan

atan

acosh

cacosh

acosh

asinh

casinh

asinh

atanh

catanh

atanh

cos

ccos

cos

sin

csin

sin

tan

ctan

tan

cosh

ccosh

cosh

sinh

csinh

sinh

tanh

ctanh

tanh

exp

cexp

exp

log

clog

log

pow

cpow

pow

sqrt

csqrt

sqrt

fabs

cabs

fabs

If at least one argument for a generic parameter is complex, then use of the macro invokes a complex function; otherwise, use of the macro invokes a real function.

For each unsuffixed function in <math.h> without a c-prefixed counterpart in <complex.h>, the corresponding type-generic macro has the same name as the function. These type-generic macros are:

atan2     fma     llround     remainder
cbrt       fmax    log10       remquo
ceil       fmin    log1p       rint
copysign   fmod    log2        round
erf        frwxp   logb        scalbn
erfc       hypot   lrint       scalbln
exp2       ilogb   lround      tgamma
expm1      ldexp   nearbyint   trunc
fdim       lgamma  nextafter
floor      llrint  nexttoward

If all arguments for generic parameters are real, then use of the macro invokes a real function; otherwise, use of the macro results in undefined behavior.

For each unsuffixed function in <complex.h> that is not a c-prefixed counterpart to a function in <math.h>, the corresponding type-generic macro has the same name as the function. These type-generic macros are:

carg cimag conj cproj creal

Use of the macro with any real or complex argument invokes a complex function.

EXAMPLE With the declarations

#include <tgmath.h>
int n;
float f;
double d;
long double ld;
float complex fc;
double complex dc;
long double complex ldc;

functions invoked by use of type-generic macros are shown in the following table:

macro use

invokes

exp(n)

exp(n), the function

acosh(f)

acoshf(f)

sin(d)

sin(d), the function

atan(ld)

atanl(ld)

log(fc)

clogf(fc)

sqrt(dc)

csqrt(dc)

pow(ldc, f)

cpowl(ldc, f)

remainder(n, n)

remainder(n, n), the function

nextafter(d, f)

nextafter(d, f), the function

nexttoward(f, ld)

nexttowardf(f, ld)

copysign(n, ld)

copysignl(n, ld)

ceil(fc)

undefined behavior

rint(dc)

undefined behavior

fmax(ldc, ld)

undefined behavior

carg(n)

carg(n), the function

cproj(f)

cprojf(f)

creal(d)

creal(d), the function

cimag(ld)

cimagl(ld)

fabs(fc)

cabsf(fc)

carg(dc)

carg(dc), the function

cproj(ldc)

cprojl(ldc)