[goffice] IMPOWER: more accuracy for complex^real.

[Morten Welinder <mortenw src gnome org>]

commit 7f35cd938500e793ef34d7661f251c77565d4c4b
Author: Morten Welinder <terra gnome org>
Date:   Fri Dec 6 16:38:31 2013 -0500

    IMPOWER: more accuracy for complex^real.

 goffice/math/go-complex.c |   32 +++++++++++++++++++++++++++-----
 1 files changed, 27 insertions(+), 5 deletions(-)
---
diff --git a/goffice/math/go-complex.c b/goffice/math/go-complex.c
index bb227b5..f7dc62e 100644
--- a/goffice/math/go-complex.c
+++ b/goffice/math/go-complex.c
@@ -278,11 +278,33 @@ SUFFIX(go_complex_sqrt) (SUFFIX(GOComplex) *dst, SUFFIX(GOComplex) const *src)
 void
 SUFFIX(go_complex_pow) (SUFFIX(GOComplex) *dst, SUFFIX(GOComplex) const *a, SUFFIX(GOComplex) const *b)
 {
-       if (SUFFIX(go_complex_zero_p) (a) && SUFFIX(go_complex_real_p) (b)) {
-               if (b->re <= 0)
-                       SUFFIX(go_complex_invalid) (dst);
-               else
-                       SUFFIX(go_complex_real) (dst, 0);
+       if (SUFFIX(go_complex_real_p) (a) && SUFFIX(go_complex_real_p) (b)) {
+               SUFFIX(go_complex_init) (dst, pow (a->re, b->re), 0);
+       } else if (SUFFIX(go_complex_real_p) (b)) {
+               DOUBLE p = SUFFIX(fabs) (b->re);
+               DOUBLE r, arg;
+               SUFFIX(GOComplex) t;
+
+               if (p == 0) {
+                       SUFFIX(go_complex_init) (dst, 1, 0);
+                       return;
+               }
+
+               arg = SUFFIX(go_complex_angle_pi) (a);
+               if (p >= 2) {
+                       r = SUFFIX(pow) (a->re * a->re + a->im * a->im, p / 2);
+               } else {
+                       r = SUFFIX(pow) (SUFFIX(hypot) (a->re, a->im), p);
+               }
+
+               SUFFIX(go_complex_from_polar_pi) (&t, r, arg * p);
+               if (b->re > 0)
+                       *dst = t;
+               else {
+                       SUFFIX(GOComplex) one;
+                       one.re = 1; one.im = 0;
+                       SUFFIX(go_complex_div) (dst, &one, &t);
+               }
        } else {
                DOUBLE res_r, res_a;
                SUFFIX(GOQuad) qr, qa, qb, qarg;