diff options
| -rw-r--r-- | Objects/floatobject.c | 72 |
1 files changed, 54 insertions, 18 deletions
diff --git a/Objects/floatobject.c b/Objects/floatobject.c index a2eba51aec..60899c921c 100644 --- a/Objects/floatobject.c +++ b/Objects/floatobject.c @@ -316,38 +316,74 @@ float_divmod(v, w) return mkvalue("(dd)", div, mod); } +double powu(x, n) + double x; + long n; +{ + double r = 1.; + double p = x; + long mask = 1; + while (mask > 0 && n >= mask) { + if (n & mask) + r *= p; + mask <<= 1; + p *= p; + } + return r; +} + +double powi(x, n) + double x; + long n; +{ + if (n > 10000 || n < -10000) + return pow(x, (double) n); + else if (n > 0) + return powu(x, n); + else + return 1./powu(x, -n); +} + static object * float_pow(v, w, z) floatobject *v; - floatobject *w; + object *w; floatobject *z; { double iv, iw, ix; - iv = v->ob_fval; - iw = w->ob_fval; + long intw; /* XXX Doesn't handle overflows if z!=None yet; it may never do so :( * The z parameter is really only going to be useful for integers and * long integers. Maybe something clever with logarithms could be done. * [AMK] */ - /* Sort out special cases here instead of relying on pow() */ - if (iw == 0.0) { /* x**0 is 1, even 0**0 */ - if ((object *)z!=None) { - ix=fmod(1.0, z->ob_fval); - if (ix!=0 && z->ob_fval<0) ix+=z->ob_fval; - } - else ix=1.0; - return newfloatobject(ix); + iv = v->ob_fval; + iw = ((floatobject *)w)->ob_fval; + intw = (long)iw; + if (iw == intw) { + errno = 0; + ix = powi(iv, intw); } - if (iv == 0.0) { - if (iw < 0.0) { - err_setstr(ValueError, "0.0 to a negative power"); - return NULL; + else { + /* Sort out special cases here instead of relying on pow() */ + if (iw == 0.0) { /* x**0 is 1, even 0**0 */ + if ((object *)z!=None) { + ix=fmod(1.0, z->ob_fval); + if (ix!=0 && z->ob_fval<0) ix+=z->ob_fval; + } + else ix=1.0; + return newfloatobject(ix); + } + if (iv == 0.0) { + if (iw < 0.0) { + err_setstr(ValueError, "0.0 to a negative power"); + return NULL; + } + return newfloatobject(0.0); } - return newfloatobject(0.0); + errno = 0; + ix = pow(iv, iw); } - errno = 0; - ix = pow(iv, iw); CHECK(ix); if (errno != 0) { /* XXX could it be another type of error? */ |