Problem diving complex numbers

Problem diving complex numbers

[Jean Crepeau]

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There appears to be a bug in the 1.6.x releases of guile which wasn't 
there in the 1.4.1 (and probably other versions before). Simply doing

    (/ 0-1i)

will result in #.##.#i instead of the expected

    0.0+1.0i

    Jean ;-)


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Re: Problem diving complex numbers

[Kevin Ryde]

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Jean Crepeau <crep@crep.dhs.org> writes:
>
> There appears to be a bug in the 1.6.x releases of guile which wasn't 
> there in the 1.4.1 (and probably other versions before).

Yep, but those versions are prone to overflow when re or im is above
sqrt(DBL_MAX).

> Simply doing
>
>    (/ 0-1i)
>
> will result in #.##.#i

Thanks.  Looks like nobody ever divided by -i before :).  I think it's
meant to be like:


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--- numbers.c.~1.135.2.20.~	2005-02-21 09:50:34.000000000 +1100
+++ numbers.c	2005-04-29 14:19:10.535828592 +1000
@@ -3738,7 +3738,7 @@
     } else if (SCM_COMPLEXP (x)) {
       double r = SCM_COMPLEX_REAL (x);
       double i = SCM_COMPLEX_IMAG (x);
-      if (r <= i) {
+      if (fabs(r) <= fabs(i)) {
 	double t = r / i;
 	double d = i * (1.0 + t * t);
 	return scm_make_complex (t / d, -1.0 / d);
@@ -3782,7 +3782,7 @@
       {
 	double r = SCM_COMPLEX_REAL (y);
 	double i = SCM_COMPLEX_IMAG (y);
-	if (r <= i) {
+        if (fabs(r) <= fabs(i)) {
 	  double t = r / i;
 	  double d = i * (1.0 + t * t);
 	  return scm_make_complex ((a * t) / d,  -a / d);
@@ -3873,7 +3873,7 @@
     } else if (SCM_COMPLEXP (y)) {
       double ry = SCM_COMPLEX_REAL (y);
       double iy = SCM_COMPLEX_IMAG (y);
-      if (ry <= iy) {
+      if (fabs(ry) <= fabs(iy)) {
 	double t = ry / iy;
 	double d = iy * (1.0 + t * t);
 	return scm_make_complex ((rx * t + ix) / d, (ix * t - rx) / d);

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