conjf, conj, conjl - cppreference.com

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# conjf, conj, conjl

From cppreference.com
< c‎ | numeric‎ | complex

Defined in header `<complex.h>` |  |
float complex conjf( float complex z ); | (1) | (since C99)
double complex conj( double complex z ); | (2) | (since C99)
long double complex conjl( long double complex z ); | (3) | (since C99)
Defined in header `<tgmath.h>` |  |
#define conj( z ) | (4) | (since C99)

1-3) Computes the complex conjugate of `z` by reversing the sign of the imaginary part.
4) Type-generic macro: if `z` has type long double complex, long double imaginary, or long double, `conjl` is called. If `z` has type float complex, float imaginary, or float, `conjf` is called. If `z` has type double complex, double imaginary, double, or any integer type, `conj` is called.

### [edit] Parameters

z | - | complex argument

### [edit] Return value

The complex conjugate of `z`.

### [edit] Notes

On C99 implementations that do not implement I as _Imaginary_I, `conj` may be used to obtain complex numbers with negative zero imaginary part. In C11, the macro CMPLX is used for that purpose.

### [edit] Example

Run this code

    #include <stdio.h>
    #include <complex.h>

    int main(void)
    {
        double complex z = 1.0 + 2.0*I;
        double complex z2 = conj(z);
        printf("The conjugate of %.1f%+.1fi is %.1f%+.1fi\n",
                creal(z), cimag(z), creal(z2), cimag(z2));

        printf("Their product is %.1f%+.1fi\n", creal(z*z2), cimag(z*z2));
    }

Output:

    The conjugate of 1.0+2.0i is 1.0-2.0i
    Their product is 5.0+0.0i

### [edit] References

- C11 standard (ISO/IEC 9899:2011):

  - 7.3.9.4 The conj functions (p: 198)

  - 7.25 Type-generic math <tgmath.h> (p: 373-375)

  - G.7 Type-generic math <tgmath.h> (p: 545)

- C99 standard (ISO/IEC 9899:1999):

  - 7.3.9.3 The conj functions (p: 179)

  - 7.22 Type-generic math <tgmath.h> (p: 335-337)

  - G.7 Type-generic math <tgmath.h> (p: 480)

### [edit] See also

C++ documentation for conj

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