# C Programming/C Reference/complex.h

**complex.h** is a header file that defines functionality for complex arithmetic.^{[1]} These functions use the built-in type `complex`

which was introduced with the C99 revision of C.

This header should not be confused with the C++ standard library header `<complex>`

, which implements complex numbers in a completely different way (as a template class, `complex<T>`

).

## Macro[edit]

Universal macro:

- complex - alias of _Complex
- _Complex_I - constant, which has type "const float _Complex" and value of imaginary unit I, I*I=-1

Defined only for `C99 Annex G`-compatible compiler modes - native support of imaginary types (it is very rare because Annex G is mathematically incorrect^{[2]}):

- imaginary - alias of _Imaginary
- _Imaginary_I Expands to a constant expression of type const float _Imaginary with the value of the imaginary unit.

Universal alias of I:

- I - alias of _Imaginary_I if it is defined else - alias of _Complex_I

Application may undefine complex, imaginary, and I macros if they interfere with internal values.

## Functions[edit]

Each function declared in `complex.h`

has three versions, each of which works with a different floating-point type (`double`

, `float`

and `long double`

). Only the `double`

version of each function is listed here; to use the `float`

(or `long double`

) version, append an `f`

(or an `l`

, respectively) to the function's name.

Note that all angles are in radians.

- Basic operations

`cabs`- computes absolute value`carg`- computes argument of a complex number`cimag`- computes imaginary part of a complex number`creal`- computes real part of a complex number`conj`- computes complex conjugate`cproj`- computes complex projection into the Riemann sphere

- Exponentiation operations

`cexp`- computes complex exponential`clog`- computes complex logarithm`csqrt`- computes complex square root`cpow`- computes complex power

- Trigonometric operations

`csin`- computes complex sine`ccos`- computes complex cosine`ctan`- computes complex tangent`casin`- computes complex arc sine`cacos`- computes complex arc cosine`catan`- computes complex arc tangent

- Hyperbolic operations

`csinh`- computes complex hyperbolic sine`ccosh`- computes complex hyperbolic cosine`ctanh`- computes complex hyperbolic tangent`casinh`- computes complex hyperbolic arc sine`cacosh`- computes complex hyperbolic arc cosine`catanh`- computes complex hyperbolic arc tangent

## References[edit]

- ↑ The Single UNIX® Specification, Issue 7 from The Open Group : complex arithmetic – Base Definitions Reference,
- ↑ Dr. Dobb's journal: software tools for the professional programmer, Volume 27 "many results in Annex G are pure invention and mathematically incorrect"