_Imaginary_I - cppreference.com (original) (raw)
| | | | | ------------------------------------------ | | ----------- | | #define _Imaginary_I /* unspecified */ | | (since C99) |
The _Imaginary_I macro expands to a value of type const float _Imaginary with the value of the imaginary unit.
As with any pure imaginary number support in C, this macro is only defined if the imaginary numbers are supported.
| A compiler that defines __STDC_IEC_559_COMPLEX__ is not required to support imaginary numbers. POSIX recommends checking if the macro _Imaginary_I is defined to identify imaginary number support. | (since C99)(until C11) |
|---|---|
| Imaginary numbers are supported if __STDC_IEC_559_COMPLEX__ is defined. | (since C11) |
[edit] Notes
This macro allows for the precise way to assemble a complex number from its real and imaginary components, e.g. with (double complex)((double)x + _Imaginary_I * (double)y). This pattern was standardized in C11 as the macro CMPLX. Note that if _Complex_I is used instead, this expression is allowed to convert negative zero to positive zero in the imaginary position.
[edit] Example
Output:
z1 = 0.0+Infi z2 = NaN+Infi
[edit] References
C11 standard (ISO/IEC 9899:2011):
7.3.1/5 _Imaginary_I (p: 188)
G.6/1 _Imaginary_I (p: 537)
C99 standard (ISO/IEC 9899:1999):
7.3.1/3 _Imaginary_I (p: 170)
G.6/1 _Imaginary_I (p: 472)
[edit] See also
| | the complex unit constant i (macro constant) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | the complex or imaginary unit constant i (macro constant) [edit] |