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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@4803 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
88 lines
1.7 KiB
C
88 lines
1.7 KiB
C
/**********************************************************************
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acosh.c -
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$Author$
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$Date$
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created at: Fri Apr 12 00:34:17 JST 2002
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public domain rewrite of acosh(3), asinh(3) and atanh(3)
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**********************************************************************/
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#include <errno.h>
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#include <float.h>
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#include <math.h>
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/* DBL_MANT_DIG must be less than 4 times of bits of int */
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#ifndef DBL_MANT_DIG
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#define DBL_MANT_DIG 53 /* in this case, at least 12 digit precision */
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#endif
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#define BIG_CRITERIA_BIT (1<<DBL_MANT_DIG/2)
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#if BIG_CRITERIA_BIT > 0
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#define BIG_CRITERIA (1.0*BIG_CRITERIA_BIT)
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#else
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#define BIG_CRITERIA (1.0*(1<<DBL_MANT_DIG/4)*(1<<(DBL_MANT_DIG/2+1-DBL_MANT_DIG/4)))
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#endif
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#define SMALL_CRITERIA_BIT (1<<(DBL_MANT_DIG/3))
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#if SMALL_CRITERIA_BIT > 0
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#define SMALL_CRITERIA (1.0/SMALL_CRITERIA_BIT)
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#else
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#define SMALL_CRITERIA (1.0*(1<<DBL_MANT_DIG/4)*(1<<(DBL_MANT_DIG/3+1-DBL_MANT_DIG/4)))
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#endif
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#ifndef HAVE_ACOSH
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double
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acosh(x)
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double x;
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{
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if (x < 1)
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x = -1; /* NaN */
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else if (x == 1)
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return 0;
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else if (x > BIG_CRITERIA)
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x += x;
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else
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x += sqrt((x + 1) * (x - 1));
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return log(x);
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}
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#endif
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#ifndef HAVE_ASINH
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double
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asinh(x)
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double x;
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{
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int neg = x < 0;
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double z = fabs(x);
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if (z < SMALL_CRITERIA) return x;
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if (z < (1.0/(1<<DBL_MANT_DIG/5))) {
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double x2 = z * z;
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z *= 1 + x2 * (-1.0/6.0 + x2 * 3.0/40.0);
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}
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else if (z > BIG_CRITERIA) {
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z = log(z + z);
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}
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else {
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z = log(z + sqrt(z * z + 1));
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}
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if (neg) z = -z;
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return z;
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}
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#endif
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#ifndef HAVE_ATANH
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double
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atanh(x)
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double x;
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{
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int neg = x < 0;
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double z = fabs(x);
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if (z < SMALL_CRITERIA) return x;
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z = log(z > 1 ? -1 : (1 + z) / (1 - z)) / 2;
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if (neg) z = -z;
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return z;
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}
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#endif
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