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Added comments, fixed a broken unit test, simplify frexp().

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This commit is contained in:
Don Clugston 2009-02-27 08:05:13 +00:00
parent eb61deb82e
commit a9ee82e9fc
1 changed files with 24 additions and 23 deletions
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47
std/math.d
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@ -1,6 +1,16 @@
// Written in the D programming language // Written in the D programming language
/** /**
* Elementary mathematical functions.
*
* The functionality closely follows the IEEE754-2008 standard for
* floating-point arithmetic, including the use of camelCase names rather
* than C99-style lower case names. All of these functions behave correctly
* when presented with an infinity or NaN.
*
* Authors:
* Walter Bright, Don Clugston
*
* Macros: * Macros:
* WIKI = Phobos/StdMath * WIKI = Phobos/StdMath
* *
@ -29,10 +39,7 @@
* SQRT = &radix; * SQRT = &radix;
* HALF = ½ * HALF = ½
*/ */
/* /*
* Authors:
* Walter Bright, Don Clugston
* Copyright: * Copyright:
* Copyright (c) 2001-2005 by Digital Mars, * Copyright (c) 2001-2005 by Digital Mars,
* All Rights Reserved, * All Rights Reserved,
@ -193,10 +200,10 @@ class NotImplemented : Error
} }
} }
enum real E = 2.7182818284590452354L; /** e */ // 3.32193 fldl2t enum real E = 2.7182818284590452354L; /** e */ // 0x1.5BF0A8B1_45769535_5FF5p+1L
enum real LOG2T = 0x1.a934f0979a3715fcp+1; /** $(SUB log, 2)10 */ // 1.4427 fldl2e enum real LOG2T = 0x1.a934f0979a3715fcp+1; /** $(SUB log, 2)10 */ // 3.32193 fldl2t
enum real LOG2E = 0x1.71547652b82fe178p+0; /** $(SUB log, 2)e */ // 0.30103 fldlg2 enum real LOG2E = 0x1.71547652b82fe178p+0; /** $(SUB log, 2)e */ // 1.4427 fldl2e
enum real LOG2 = 0x1.34413509f79fef32p-2; /** $(SUB log, 10)2 */ enum real LOG2 = 0x1.34413509f79fef32p-2; /** $(SUB log, 10)2 */ // 0.30103 fldlg2
enum real LOG10E = 0.43429448190325182765; /** $(SUB log, 10)e */ enum real LOG10E = 0.43429448190325182765; /** $(SUB log, 10)e */
enum real LN2 = 0x1.62e42fefa39ef358p-1; /** ln 2 */ // 0.693147 fldln2 enum real LN2 = 0x1.62e42fefa39ef358p-1; /** ln 2 */ // 0.693147 fldln2
enum real LN10 = 2.30258509299404568402; /** ln 10 */ enum real LN10 = 2.30258509299404568402; /** ln 10 */
@ -638,7 +645,7 @@ creal coshisinh(real x)
return y*0.5 + 0.5i * copysign(y, x); return y*0.5 + 0.5i * copysign(y, x);
} else { } else {
real y = expm1(x); real y = expm1(x);
return (y + 1.0 + 1.0/(y+1.0)) * 0.5 + 0.5i * y / (y+1) * (y+2); return (y + 1.0 + 1.0/(y + 1.0)) * 0.5 + 0.5i * y / (y+1) * (y+2);
} }
} }
@ -1060,10 +1067,9 @@ float exp2(float x) { return exp2(cast(real)x); }
unittest{ unittest{
assert(exp2(0.5L)== SQRT2); assert(exp2(0.5L)== SQRT2);
assert(exp2(8L) == 256.0); assert(exp2(8.0L) == 256.0);
assert(exp2(-9L)== 1.0L/512.0); assert(exp2(-9.0L)== 1.0L/512.0);
assert(exp(3) == E*E*E); assert(exp(3.0L) == E*E*E);
} }
/** /**
@ -1135,22 +1141,17 @@ real frexp(real value, out int exp)
} }
} else { } else {
exp = ex - F.EXPBIAS; exp = ex - F.EXPBIAS;
vu[F.EXPPOS_SHORT] = vu[F.EXPPOS_SHORT] = (0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE;
cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE);
} }
} else if (!*vl) { } else if (!*vl) {
// value is +-0.0 // value is +-0.0
exp = 0; exp = 0;
} else { } else {
// denormal // denormal
int i = -0x3FFD; value *= F.POW2MANTDIG;
do { ex = vu[F.EXPPOS_SHORT] & F.EXPMASK;
i--; exp = ex - F.EXPBIAS - 63;
*vl <<= 1; vu[F.EXPPOS_SHORT] = (0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE;
} while (*vl > 0);
exp = i;
vu[F.EXPPOS_SHORT] =
cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT]) | 0x3FFE);
} }
} else static if (real.mant_dig == 113) { // quadruple } else static if (real.mant_dig == 113) { // quadruple
if (ex) { // If exponent is non-zero if (ex) { // If exponent is non-zero
@ -1206,7 +1207,7 @@ real frexp(real value, out int exp)
sgn = cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT])| 0x3FE0); sgn = cast(ushort)((0x8000 & vu[F.EXPPOS_SHORT])| 0x3FE0);
*vl &= 0x7FFF_FFFF_FFFF_FFFF; *vl &= 0x7FFF_FFFF_FFFF_FFFF;
int i = -0x3FD+11; int i = -0x3FD + 11;
do { do {
i--; i--;
*vl <<= 1; *vl <<= 1;