jacob navia wrote:
hi
I am trying to use the complex data type.
Consider this code, taken from the cclib library:
struct complex csqrt(Cpx z)
{ double r;
r=sqrt(z.re*z.re+z.im*z.im);
r=sqrt(ldexp(r+fabs(z.re),-1));
if(r==0.) z.re=z.im=0.;
else{
if(z.re>=0.){ z.re=r; z.im=ldexp(z.im/r,-1);}
else{ z.re=ldexp(fabs(z.im)/r,-1);
if(z.im>=0.) z.im=r; else z.im= -r;
}
}
return z;
}
Now, this works in lcc-win easily because lcc-win
allows access to the real and imaginary parts of the complex
data type easily, using
z.re (real part)
and
ze.im
for the imaginary part.
I do not see how can be this written in standard C.
Has anyone an idea?
Your function works just fine in standard C. Check the following:
#include <math.h>
#include <stdio.h>
/* if you don't have <complex.h>, remove or comment out the line below */
#define USE_COMPLEX_H
typedef struct cmplx
{
double re, im;
} Cpx;
/* 'cmplx' chosen for the name of the struct since 'complex' should be
<complex.h*/
Cpx Csqrt
/* renamed because csqrt should be in <complex.h*/
(Cpx z)
{
double r;
r = sqrt(z.re * z.re + z.im * z.im);
r = sqrt(ldexp(r + fabs(z.re), -1));
if (r == 0.)
z.re = z.im = 0.;
else {
if (z.re >= 0.) {
z.re = r;
z.im = ldexp(z.im / r, -1);
}
else {
z.re = ldexp(fabs(z.im) / r, -1);
if (z.im >= 0.)
z.im = r;
else
z.im = -r;
}
}
return z;
}
Cpx Csquare(Cpx z)
{
Cpx r;
r.re = z.re * z.re - z.im * z.im;
r.im = 2 * z.re * z.im;
return r;
}
#if defined(USE_COMPLEX_H)
#include <complex.h>
double complex Csqrt2(double complex z)
{
double r;
r = sqrt(creal(z) * creal(z) + cimag(z) * cimag(z));
r = sqrt(ldexp(r + fabs(creal(z)), -1));
if (r == 0.)
z = 0.;
else {
if (creal(z) >= 0.) {
z = r + ldexp(cimag(z) / r, -1) * I;
}
else {
z = ldexp(fabs(cimag(z)) / r,
-1) + (cimag(z) >= 0. ? r : -r) * I;
}
}
return z;
}
#endif
int main(void)
{
Cpx x, y, z;
#if defined(USE_COMPLEX_H)
double complex cx, cy, cz;
#endif
int i, j;
printf("Using the function Jacob Navia provided,\n"
"with a struct for complex types.\n\n");
for (i = -2; i < 3; i++)
for (j = -2; j < 3; j++) {
x.re = i;
x.im = j;
y = Csqrt(x);
z = Csquare(y);
printf("y = Csqrt(%g+%gi)) = %g+%gi, y*y=%g+%gi\n",
x.re, x.im, y.re, y.im, z.re, z.im);
}
#if defined(USE_COMPLEX_H)
printf("\nUsing the function Jacob Navia provided,\n"
"rewritten to use complex types.\n\n");
for (i = -2; i < 3; i++)
for (j = -2; j < 3; j++) {
cx = i + j * I;
cy = Csqrt2(cx);
cz = cy * cy;
printf("y = Csqrt2(%g+%gi)) = %g+%gi, y*y=%g+%gi\n",
creal(cx), cimag(cx),
creal(cy), cimag(cy),
creal(cz), cimag(cz));
}
#endif
return 0;
}
[Output]
Using the function Jacob Navia provided,
with a struct for complex types.
y = Csqrt(-2+-2i)) = 0.643594+-1.55377i, y*y=-2+-2i
y = Csqrt(-2+-1i)) = 0.343561+-1.45535i, y*y=-2+-1i
y = Csqrt(-2+0i)) = 0+1.41421i, y*y=-2+0i
y = Csqrt(-2+1i)) = 0.343561+1.45535i, y*y=-2+1i
y = Csqrt(-2+2i)) = 0.643594+1.55377i, y*y=-2+2i
y = Csqrt(-1+-2i)) = 0.786151+-1.27202i, y*y=-1+-2i
y = Csqrt(-1+-1i)) = 0.45509+-1.09868i, y*y=-1+-1i
y = Csqrt(-1+0i)) = 0+1i, y*y=-1+0i
y = Csqrt(-1+1i)) = 0.45509+1.09868i, y*y=-1+1i
y = Csqrt(-1+2i)) = 0.786151+1.27202i, y*y=-1+2i
y = Csqrt(0+-2i)) = 1+-1i, y*y=0+-2i
y = Csqrt(0+-1i)) = 0.707107+-0.707107i, y*y=1.5702e-16+-1i
y = Csqrt(0+0i)) = 0+0i, y*y=0+0i
y = Csqrt(0+1i)) = 0.707107+0.707107i, y*y=1.5702e-16+1i
y = Csqrt(0+2i)) = 1+1i, y*y=0+2i
y = Csqrt(1+-2i)) = 1.27202+-0.786151i, y*y=1+-2i
y = Csqrt(1+-1i)) = 1.09868+-0.45509i, y*y=1+-1i
y = Csqrt(1+0i)) = 1+0i, y*y=1+0i
y = Csqrt(1+1i)) = 1.09868+0.45509i, y*y=1+1i
y = Csqrt(1+2i)) = 1.27202+0.786151i, y*y=1+2i
y = Csqrt(2+-2i)) = 1.55377+-0.643594i, y*y=2+-2i
y = Csqrt(2+-1i)) = 1.45535+-0.343561i, y*y=2+-1i
y = Csqrt(2+0i)) = 1.41421+0i, y*y=2+0i
y = Csqrt(2+1i)) = 1.45535+0.343561i, y*y=2+1i
y = Csqrt(2+2i)) = 1.55377+0.643594i, y*y=2+2i
Using the function Jacob Navia provided,
rewritten to use __complex__ types.
y = Csqrt2(-2+-2i)) = 0.643594+-1.55377i, y*y=-2+-2i
y = Csqrt2(-2+-1i)) = 0.343561+-1.45535i, y*y=-2+-1i
y = Csqrt2(-2+0i)) = 0+1.41421i, y*y=-2+0i
y = Csqrt2(-2+1i)) = 0.343561+1.45535i, y*y=-2+1i
y = Csqrt2(-2+2i)) = 0.643594+1.55377i, y*y=-2+2i
y = Csqrt2(-1+-2i)) = 0.786151+-1.27202i, y*y=-1+-2i
y = Csqrt2(-1+-1i)) = 0.45509+-1.09868i, y*y=-1+-1i
y = Csqrt2(-1+0i)) = 0+1i, y*y=-1+0i
y = Csqrt2(-1+1i)) = 0.45509+1.09868i, y*y=-1+1i
y = Csqrt2(-1+2i)) = 0.786151+1.27202i, y*y=-1+2i
y = Csqrt2(0+-2i)) = 1+-1i, y*y=0+-2i
y = Csqrt2(0+-1i)) = 0.707107+-0.707107i, y*y=1.5702e-16+-1i
y = Csqrt2(0+0i)) = 0+0i, y*y=0+0i
y = Csqrt2(0+1i)) = 0.707107+0.707107i, y*y=1.5702e-16+1i
y = Csqrt2(0+2i)) = 1+1i, y*y=0+2i
y = Csqrt2(1+-2i)) = 1.27202+-0.786151i, y*y=1+-2i
y = Csqrt2(1+-1i)) = 1.09868+-0.45509i, y*y=1+-1i
y = Csqrt2(1+0i)) = 1+0i, y*y=1+0i
y = Csqrt2(1+1i)) = 1.09868+0.45509i, y*y=1+1i
y = Csqrt2(1+2i)) = 1.27202+0.786151i, y*y=1+2i
y = Csqrt2(2+-2i)) = 1.55377+-0.643594i, y*y=2+-2i
y = Csqrt2(2+-1i)) = 1.45535+-0.343561i, y*y=2+-1i
y = Csqrt2(2+0i)) = 1.41421+0i, y*y=2+0i
y = Csqrt2(2+1i)) = 1.45535+0.343561i, y*y=2+1i
y = Csqrt2(2+2i)) = 1.55377+0.643594i, y*y=2+2i