Defined in header <complex.h> | ||
---|---|---|
#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 |
(since C99) (until C11) |
Imaginary numbers are supported if | (since C11) |
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.
#include <stdio.h> #include <complex.h> #include <math.h> int main(void) { double complex z1 = 0.0 + INFINITY * _Imaginary_I; printf("z1 = %.1f%+.1fi\n", creal(z1), cimag(z1)); double complex z2 = 0.0 + INFINITY * _Complex_I; printf("z2 = %.1f%+.1fi\n", creal(z2), cimag(z2)); }
Output:
z1 = 0.0+Infi z2 = NaN+Infi
(C99) | the complex unit constant i (macro constant) |
(C99) | the complex or imaginary unit constant i (macro constant) |
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