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@ -21,24 +21,28 @@ |
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* |
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* |
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* Special cases: |
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* Special cases: |
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* 1. (anything) ** 0 is 1 |
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* 1. (anything) ** 0 is 1 |
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* 2. (anything) ** 1 is itself |
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* 2. 1 ** (anything) is 1 |
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* 3. (anything except 1) ** NAN is NAN, 1 ** NAN is 1 |
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* 3. (anything except 1) ** NAN is NAN |
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* 4. NAN ** (anything except 0) is NAN |
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* 4. NAN ** (anything except 0) is NAN |
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* 5. +-(|x| > 1) ** +INF is +INF |
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* 5. +-(|x| > 1) ** +INF is +INF |
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* 6. +-(|x| > 1) ** -INF is +0 |
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* 6. +-(|x| > 1) ** -INF is +0 |
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* 7. +-(|x| < 1) ** +INF is +0 |
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* 7. +-(|x| < 1) ** +INF is +0 |
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* 8. +-(|x| < 1) ** -INF is +INF |
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* 8. +-(|x| < 1) ** -INF is +INF |
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* 9. +-1 ** +-INF is 1 |
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* 9. -1 ** +-INF is 1 |
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* 10. +0 ** (+anything except 0, NAN) is +0 |
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* 10. +0 ** (+anything except 0, NAN) is +0 |
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* 11. -0 ** (+anything except 0, NAN, odd integer) is +0 |
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* 11. -0 ** (+anything except 0, NAN, odd integer) is +0 |
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* 12. +0 ** (-anything except 0, NAN) is +INF |
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* 12. +0 ** (-anything except 0, NAN) is +INF, raise divbyzero |
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* 13. -0 ** (-anything except 0, NAN, odd integer) is +INF |
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* 13. -0 ** (-anything except 0, NAN, odd integer) is +INF, raise divbyzero |
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* 14. -0 ** (odd integer) = -( +0 ** (odd integer) ) |
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* 14. -0 ** (+odd integer) is -0 |
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* 15. +INF ** (+anything except 0,NAN) is +INF |
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* 15. -0 ** (-odd integer) is -INF, raise divbyzero |
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* 16. +INF ** (-anything except 0,NAN) is +0 |
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* 16. +INF ** (+anything except 0,NAN) is +INF |
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* 17. -INF ** (anything) = -0 ** (-anything) |
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* 17. +INF ** (-anything except 0,NAN) is +0 |
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* 18. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer) |
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* 18. -INF ** (+odd integer) is -INF |
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* 19. (-anything except 0 and inf) ** (non-integer) is NAN |
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* 19. -INF ** (anything) = -0 ** (-anything), (anything except odd integer) |
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* 20. (anything) ** 1 is (anything) |
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* 21. (anything) ** -1 is 1/(anything) |
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* 22. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer) |
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* 23. (-anything except 0 and inf) ** (non-integer) is NAN |
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* |
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* |
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* Accuracy: |
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* Accuracy: |
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* pow(x,y) returns x**y nearly rounded. In particular |
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* pow(x,y) returns x**y nearly rounded. In particular |
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@ -98,18 +102,16 @@ double pow(double x, double y) |
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ix = hx & 0x7fffffff; |
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ix = hx & 0x7fffffff; |
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iy = hy & 0x7fffffff; |
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iy = hy & 0x7fffffff; |
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/* y == 0.0: x**0 = 1 */ |
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/* x**0 = 1, even if x is NaN */ |
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if ((iy|ly) == 0) |
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if ((iy|ly) == 0) |
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return 1.0; |
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return 1.0; |
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/* 1**y = 1, even if y is NaN */ |
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/* x == 1: 1**y = 1, even if y is NaN */ |
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if (hx == 0x3ff00000 && lx == 0) |
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if (hx == 0x3ff00000 && lx == 0) |
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return 1.0; |
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return 1.0; |
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/* NaN if either arg is NaN */ |
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/* y != 0.0: result is NaN if either arg is NaN */ |
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if (ix > 0x7ff00000 || (ix == 0x7ff00000 && lx != 0) || |
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if (ix > 0x7ff00000 || (ix == 0x7ff00000 && lx != 0) || |
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iy > 0x7ff00000 || (iy == 0x7ff00000 && ly != 0)) |
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iy > 0x7ff00000 || (iy == 0x7ff00000 && ly != 0)) |
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return (x+0.0) + (y+0.0); |
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return x + y; |
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/* determine if y is an odd int when x < 0
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/* determine if y is an odd int when x < 0
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* yisint = 0 ... y is not an integer |
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* yisint = 0 ... y is not an integer |
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@ -142,13 +144,10 @@ double pow(double x, double y) |
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else if (ix >= 0x3ff00000) /* (|x|>1)**+-inf = inf,0 */ |
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else if (ix >= 0x3ff00000) /* (|x|>1)**+-inf = inf,0 */ |
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return hy >= 0 ? y : 0.0; |
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return hy >= 0 ? y : 0.0; |
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else /* (|x|<1)**+-inf = 0,inf */ |
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else /* (|x|<1)**+-inf = 0,inf */ |
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return hy < 0 ? -y : 0.0; |
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return hy >= 0 ? 0.0 : -y; |
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} |
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if (iy == 0x3ff00000) { /* y is +-1 */ |
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if (hy < 0) |
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return 1.0/x; |
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return x; |
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} |
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} |
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if (iy == 0x3ff00000) /* y is +-1 */ |
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return hy >= 0 ? x : 1.0/x; |
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if (hy == 0x40000000) /* y is 2 */ |
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if (hy == 0x40000000) /* y is 2 */ |
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return x*x; |
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return x*x; |
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if (hy == 0x3fe00000) { /* y is 0.5 */ |
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if (hy == 0x3fe00000) { /* y is 0.5 */ |
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@ -174,19 +173,13 @@ double pow(double x, double y) |
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} |
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} |
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} |
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} |
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/* CYGNUS LOCAL + fdlibm-5.3 fix: This used to be
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s = 1.0; /* sign of result */ |
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n = (hx>>31)+1; |
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if (hx < 0) { |
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but ANSI C says a right shift of a signed negative quantity is |
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if (yisint == 0) /* (x<0)**(non-int) is NaN */ |
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implementation defined. */ |
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n = ((uint32_t)hx>>31) - 1; |
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/* (x<0)**(non-int) is NaN */ |
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if ((n|yisint) == 0) |
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return (x-x)/(x-x); |
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return (x-x)/(x-x); |
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if (yisint == 1) /* (x<0)**(odd int) */ |
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s = 1.0; /* s (sign of result -ve**odd) = -1 else = 1 */ |
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s = -1.0; |
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if ((n|(yisint-1)) == 0) |
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} |
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s = -1.0;/* (-ve)**(odd int) */ |
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/* |y| is huge */ |
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/* |y| is huge */ |
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if (iy > 0x41e00000) { /* if |y| > 2**31 */ |
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if (iy > 0x41e00000) { /* if |y| > 2**31 */ |
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