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Fix float math.pow when number was negative and power was odd (#1492)

This commit is contained in:
Luís Fonseca 2016-09-07 21:45:06 +01:00 committed by Arnim Läuger
parent 3109497b33
commit 19f80abb32
1 changed files with 9 additions and 2 deletions
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11
app/libc/c_math.c
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@ -59,6 +59,7 @@ double pow(double x, double y)
{ {
double frexp(), g, ldexp(), r, u1, u2, v, w, w1, w2, y1, y2, z; double frexp(), g, ldexp(), r, u1, u2, v, w, w1, w2, y1, y2, z;
int iw1, m, p; int iw1, m, p;
bool flipsignal = false;
if (y == 0.0) if (y == 0.0)
return (1.0); return (1.0);
@ -67,7 +68,7 @@ double pow(double x, double y)
if (x == 0.0) if (x == 0.0)
{ {
if (y > 0.0) if (y > 0.0)
return (x); return 0.0;
//cmemsg(FP_POWO, &y); //cmemsg(FP_POWO, &y);
//return(HUGE); //return(HUGE);
} }
@ -75,6 +76,11 @@ double pow(double x, double y)
{ {
//cmemsg(FP_POWN, &x); //cmemsg(FP_POWN, &x);
x = -x; x = -x;
if (y != (int) y) { // if y is fractional, then this woud result in a complex number
return NAN;
}
flipsignal = ((int) y) & 1;
} }
} }
g = frexp(x, &m); g = frexp(x, &m);
@ -125,7 +131,8 @@ double pow(double x, double y)
p = 16 * m - iw1; p = 16 * m - iw1;
z = ((((((q7 * w2 + q6) * w2 + q5) * w2 + q4) * w2 + q3) * w2 + q2) * w2 + q1) * w2; z = ((((((q7 * w2 + q6) * w2 + q5) * w2 + q4) * w2 + q3) * w2 + q2) * w2 + q1) * w2;
z = a1[p] + a1[p] * z; z = a1[p] + a1[p] * z;
return (ldexp(z, m)); double res = ldexp(z, m);
return flipsignal ? -res : res;
} }
#if 0 #if 0