/usr/share/calc/solve.cal is in apcalc-common 2.12.5.0-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 | /*
* solve - solve f(x) = 0 to within the desired error value for x
*
* Copyright (C) 1999 David I. Bell
*
* Calc is open software; you can redistribute it and/or modify it under
* the terms of the version 2.1 of the GNU Lesser General Public License
* as published by the Free Software Foundation.
*
* Calc is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
* Public License for more details.
*
* A copy of version 2.1 of the GNU Lesser General Public License is
* distributed with calc under the filename COPYING-LGPL. You should have
* received a copy with calc; if not, write to Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* @(#) $Revision: 30.3 $
* @(#) $Id: solve.cal,v 30.3 2013/08/11 08:41:38 chongo Exp $
* @(#) $Source: /usr/local/src/bin/calc/cal/RCS/solve.cal,v $
*
* Under source code control: 1990/02/15 01:50:37
* File existed as early as: before 1990
*
* Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
*/
/*
* Solve the equation f(x) = 0 to within the desired error value for x.
* The function 'f' must be defined outside of this routine, and the low
* and high values are guesses which must produce values with opposite signs.
*/
define solve(low, high, epsilon)
{
local flow, fhigh, fmid, mid, places;
if (isnull(epsilon))
epsilon = epsilon();
if (epsilon <= 0)
quit "Non-positive epsilon value";
places = highbit(1 + int(1/epsilon)) + 1;
flow = f(low);
if (abs(flow) < epsilon)
return low;
fhigh = f(high);
if (abs(fhigh) < epsilon)
return high;
if (sgn(flow) == sgn(fhigh))
quit "Non-opposite signs";
while (1) {
mid = bround(high - fhigh * (high - low) / (fhigh - flow),
places);
if ((mid == low) || (mid == high))
places++;
fmid = f(mid);
if (abs(fmid) < epsilon)
return mid;
if (sgn(fmid) == sgn(flow)) {
low = mid;
flow = fmid;
} else {
high = mid;
fhigh = fmid;
}
}
}
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