complex type

[Mantorok Redgormor]

With what specifier do I use to print a variable of a complex type?
The man page for printf doesn't even say.
- nethlek

[Martin Ambuhl]

Mantorok Redgormor wrote:

With what specifier do I use to print a variable of a complex type?
The man page for printf doesn't even say.

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

int main(void)
{
complex c = 5 + 3*I;
printf("%g + %gi\n", creal(c), cimag(c));
return 0;
}

--
Martin Ambuhl

[Irrwahn Grausewitz]

ne*****@tokyo.c om (Mantorok Redgormor) wrote:

With what specifier do I use to print a variable of a complex type?
The man page for printf doesn't even say.

Unfortunately there is no printf format conversion specifier for
printing complex numbers directely, but ISO/IEC 9899:1999 says:

6.2.5 Types
[...]
13 Each complex type has the same representation and alignment
requirements as an array type containing exactly two elements of the
corresponding real type; the first element is equal to the real part,
and the second element to the imaginary part, of the complex number.
[...]

Thus you can printf the value of an object of complex type like an array
of 2 of the underlying real type, for example:

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

int main( void )
{
double complex cmplvar = 5.0 + 3.0 * I;
printf ("cmplvar = %f+%fi\n", cmplvar[0], cmplvar[1] );
return 0;
}

Untested code; the implementation at hand doesn't support complex types.

HTH
Regards
--
Irrwahn
(ir*******@free net.de)

[Jeremy Yallop]

Irrwahn Grausewitz wrote:

ne*****@tokyo.c om (Mantorok Redgormor) wrote:

With what specifier do I use to print a variable of a complex type?
The man page for printf doesn't even say.

Unfortunately there is no printf format conversion specifier for
printing complex numbers directely, but ISO/IEC 9899:1999 says:

6.2.5 Types
[...]
13 Each complex type has the same representation and alignment
requirements as an array type containing exactly two elements of the
corresponding real type; the first element is equal to the real part,
and the second element to the imaginary part, of the complex number.
[...]

Thus you can printf the value of an object of complex type like an array
of 2 of the underlying real type, for example:

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

int main( void )
{
double complex cmplvar = 5.0 + 3.0 * I;
printf ("cmplvar = %f+%fi\n", cmplvar[0], cmplvar[1] );

"cmplvar" is not an array (or pointer), so you can't use the subscript
operator on it, despite the guarantees about representation and
alignment quoted above. You can do nasty things with casts to make
your example work, but creal() and cimag() are the right solution in
this case.

Jeremy.

[Irrwahn Grausewitz]

Jeremy Yallop <je****@jdyallo p.freeserve.co. uk> wrote:

Irrwahn Grausewitz wrote:

printf ("cmplvar = %f+%fi\n", cmplvar[0], cmplvar[1] );
"cmplvar" is not an array (or pointer), so you can't use the subscript
operator on it, despite the guarantees about representation and
alignment quoted above. You can do nasty things with casts to make
your example work,

Indeed.
but creal() and cimag() are the right solution in
this case.

Definitely! What was I thinking? Fortunately Martin Ambuhl posted a
correct example. My apologies for posting nonsense.

Regards
--
Irrwahn
(ir*******@free net.de)