operations on complex numbers in C99

[David Marsh]

I understand that C99 supports a complex type and complex
arithmetic. There is nothing about it in the FAQ and online
searches turned up very little except synopses. Can anyone point
me toward sources or give examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

Thanks,
David

[Ian Collins]

David Marsh wrote:

I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up very
little except synopses. Can anyone point me toward sources or give
examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

The only examples I have seen are in Annex G of the standard, not the
best (being in standards speak!), but they should be enough to get you
going.

--
Ian Collins.

[Keith Thompson]

David Marsh <dm****@mail.co mwrites:

I understand that C99 supports a complex type and complex
arithmetic. There is nothing about it in the FAQ and online searches
turned up very little except synopses. Can anyone point me toward
sources or give examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

The latest draft of the standard is
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf>.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[CBFalconer]

David Marsh wrote:

>
I understand that C99 supports a complex type and complex
arithmetic. There is nothing about it in the FAQ and online
searches turned up very little except synopses. Can anyone point
me toward sources or give examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

Try N1124 and/or N869. You can get N869 in BZ2'd text form from:

<http://cbfalconer.home .att.net/download/>

--
"Vista is finally secure from hacking. No one is going to 'hack'
the product activation and try and steal the o/s. Anyone smart
enough to do so is also smart enough not to want to bother."

--
Posted via a free Usenet account from http://www.teranews.com

[David Marsh]

Ian Collins wrote:

David Marsh wrote:

>>I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up very
little except synopses. Can anyone point me toward sources or give
examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

The only examples I have seen are in Annex G of the standard, not the
best (being in standards speak!), but they should be enough to get you
going.

Sheesh! Much easier to write my own library than to make sense of
that gobbledygook. But thanks anyway.

David

[jacob navia]

David Marsh wrote:

I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up very
little except synopses. Can anyone point me toward sources or give
examples which show how to:

-declare a complex variable

double _Complex myvar = 5.778 + 45.87*I;
(standard notation)

Some compilers like lcc-win32 or gcc use
double _Complex myvar = 5.778 + 45.87i;
but that is not standard.

-assign the real and imaginary parts

creal(myvar)=8. 0;
cimag(myvar)=6. 9;

-perform the basic +,-,*,/ operations on complex numbers

(myvar+2)/(myvar-4)

Nothing special

>
Thanks,
David

[jacob navia]

David Marsh wrote:

Ian Collins wrote:

>David Marsh wrote:

>>I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up very
little except synopses. Can anyone point me toward sources or give
examples which show how to:

-declare a complex variable
-assign the real and imaginary parts
-perform the basic +,-,*,/ operations on complex numbers

The only examples I have seen are in Annex G of the standard, not the
best (being in standards speak!), but they should be enough to get you
going.

Sheesh! Much easier to write my own library than to make sense of that
gobbledygook. But thanks anyway.

David

See my answer elsethread. It is very easy.

[David Marsh]

jacob navia wrote:

David Marsh wrote:

>I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up
very little except synopses. Can anyone point me toward sources or
give examples which show how to:

-declare a complex variable

double _Complex myvar = 5.778 + 45.87*I;
(standard notation)

Some compilers like lcc-win32 or gcc use
double _Complex myvar = 5.778 + 45.87i;
but that is not standard.

>-assign the real and imaginary parts

creal(myvar)=8. 0;
cimag(myvar)=6. 9;

>-perform the basic +,-,*,/ operations on complex numbers

(myvar+2)/(myvar-4)

Nothing special

Thanks, Jacob, but I'm having a problem with the assignments
using creal() and cimag(). It works OK if the commented out lines
are used instead. What am I doing wrong?

David

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

int main(void)
{
//double _Complex z1 = 1.2 + .5 * I;
//double _Complex z2, z3;
double _Complex z1, z2, z3;

creal(z1) = 1.2; /* error */
cimag(z1) = .5; /* error */
z2 = csqrt(z1);
z3 = z1 + z2;
printf("sqrt = %g %gi\n", creal(z2), cimag(z2));
printf("z1+z2 = %g %gi\n", creal(z3), cimag(z3));

return 0;
}

C:\WINDOWS\Desk top\data>lcc cxtest.c
Error cxtest.c: 10 the left hand side of the assignment can't be
assigned to
Error cxtest.c: 11 the left hand side of the assignment can't be
assigned to
2 errors, 0 warnings

[Duncan Muirhead]

On Mon, 06 Aug 2007 16:00:22 +0200, jacob navia wrote:

David Marsh wrote:

>I understand that C99 supports a complex type and complex arithmetic.
There is nothing about it in the FAQ and online searches turned up very
little except synopses. Can anyone point me toward sources or give
examples which show how to:

-declare a complex variable

double _Complex myvar = 5.778 + 45.87*I;
(standard notation)

<snip>

>-assign the real and imaginary parts

creal(myvar)=8. 0;
cimag(myvar)=6. 9;

I don't understand the last two. Isn't creal a function returning a
double? How can that yield an lvalue?.
To set just the real part of myvar, wouldn't you have to write something
like
myvar = 8.0 + cimag(myvar)*I;
?
(For what its worth I much prefer gcc's __real__ and __imag__ operators;
with them you can write
__real__ myvar = 0.0;
)

[Keith Thompson]

jacob navia <ja***@jacob.re mcomp.frwrites:

David Marsh wrote:

>I understand that C99 supports a complex type and complex
arithmetic. There is nothing about it in the FAQ and online searches
turned up very little except synopses. Can anyone point me toward
sources or give examples which show how to:
-declare a complex variable

double _Complex myvar = 5.778 + 45.87*I;
(standard notation)

If you have '#include <complex.h>' (which is required for 'I' anyway),
you can use 'complex' rather than '_Complex'.

Some compilers like lcc-win32 or gcc use
double _Complex myvar = 5.778 + 45.87i;
but that is not standard.

and is therefore irrelevant unless you want to make your code
gratuitously non-portable.

>-assign the real and imaginary parts

creal(myvar)=8. 0;
cimag(myvar)=6. 9;

creal() and cimag() are functions, which therefore do not yield
lvalues. You can't assign to them.

>-perform the basic +,-,*,/ operations on complex numbers

(myvar+2)/(myvar-4)

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"