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Release calc version 2.11.5t4
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Landon Curt Noll
185
cscript/powerterm.calc
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185
cscript/powerterm.calc
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#!/usr/local/bin/calc -q -s -f
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/*
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* powerterm - print the argument as a sum of powers of integers
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*
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* usage:
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* powerterm [base_limit] value
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*
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* base_limit largest base we will consider (def: 10000)
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* value value to convert into sums of powers of integers
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*
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* Copyright (C) 2001 Landon Curt Noll
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*
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* Calc is open software; you can redistribute it and/or modify it under
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* the powerterm of the version 2.1 of the GNU Lesser General Public License
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* as published by the Free Software Foundation.
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*
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* Calc is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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* Public License for more details.
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*
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* A copy of version 2.1 of the GNU Lesser General Public License is
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* distributed with calc under the filename COPYING-LGPL. You should have
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* received a copy with calc; if not, write to Free Software Foundation, Inc.
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
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*
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* @(#) $Revision: 29.5 $
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* @(#) $Id: powerterm.calc,v 29.5 2001/04/25 08:41:36 chongo Exp $
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* @(#) $Source: /usr/local/src/cmd/calc/cscript/RCS/powerterm.calc,v $
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*
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* Under source code control: 2001/04/24 23:49:11
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* File existed as early as: 2001
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*
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* chongo <was here> /\oo/\ http://www.isthe.com/chongo/
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* Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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*/
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/*
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* parse args
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*/
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config("verbose_quit", 0),;
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base_lim = 10000; /* default: highest base we will consider */
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if (argv() < 2 || argv() > 3) {
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fprintf(files(2), "usage: %s [base_limit] value\n", argv(0));
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exit;
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}
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if (argv() == 3) {
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x = eval(argv(2));
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base_lim = eval(argv(1));
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} else {
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x = eval(argv(1));
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}
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if (! isint(x)) {
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fprintf(files(2), "%s: value must be an integer\n");
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exit;
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}
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if (! isint(base_lim)) {
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fprintf(files(2), "%s: base limit must be an integer\n");
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exit;
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}
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if (base_lim <= 1) {
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fprintf(files(2), "%s: base limit is too small\n");
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exit;
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}
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++base_lim;
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/*
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* setup loop variables
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*/
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term = 0; /* number of powerterm found */
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/*
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* log constants
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*/
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if (base_lim <= 2^20+1) { /* 2^20 requires ~96 Megs of memory */
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mat lni[base_lim]; /* log of integers */
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for (i=2; i < base_lim; ++i) {
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lni[i] = ln(i);
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}
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have_lni = 1; /* have lni[x] array */
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} else {
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mat lni[1]; /* not used */
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have_lni = 0; /* base_lim too large for array */
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}
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/*
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* remove nestest powers
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*/
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while (abs(x) >= base_lim) {
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/*
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* look for the nearest power
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*/
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lnx = ln(abs(x)); /* log of the remaining co-factor */
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closest = 0.5;
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base = 1;
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exponent = 0;
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if (have_lni) {
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/*
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* use pre-calculated log array when looking for the nearest power
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*/
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for (i = 2; i < base_lim; ++i) {
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/*
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* determine exponent closeness to an integer
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*/
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ex = lnx / lni[i];
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power = int(ex + 0.5);
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diff = ex - power;
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/*
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* look for a closer power
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*/
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if (abs(diff) < closest) {
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closest = abs(diff);
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base = i;
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exponent = power;
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}
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}
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} else {
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/*
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* re-calculate logs when looking for the nearest power
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*/
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for (i = 2; i < base_lim; ++i) {
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/*
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* determine exponent closeness to an integer
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*/
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ex = lnx / ln(i);
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power = int(ex + 0.5);
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diff = ex - power;
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/*
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* look for a closer power
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*/
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if (abs(diff) < closest) {
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closest = abs(diff);
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base = i;
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exponent = power;
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}
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}
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}
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/*
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* output current term and then subtract it
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*/
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if (x != 0) {
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if (x < 0) {
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print "-",;
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} else if (term > 0) {
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print "+",;
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}
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if (exponent > 1) {
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print base: "^": exponent,;
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} else {
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print base,;
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}
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}
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/*
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* subtract (or add) this near power
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*/
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if (x < 0) {
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x = x + base^exponent;
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} else {
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x = x - base^exponent;
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}
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++term;
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}
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/*
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* print the final term
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*/
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if (x < 0) {
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print "-", -x;
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} else if (x > 0) {
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print "+", x;
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} else {
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print "";
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}
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exit;
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