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factor.c
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factor.c
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/*
* Mathomatic symbolic factorizing routines, not polynomial factoring.
*
* Copyright (C) 1987-2012 George Gesslein II.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
The chief copyright holder can be contacted at [email protected], or
George Gesslein II, P.O. Box 224, Lansing, NY 14882-0224 USA.
*/
#include "includes.h"
#define ALWAYS_FACTOR_POWER 1
static int fplus_recurse(token_type *equation, int *np, int loc, int level, long v, double d, int whole_flag, int div_only);
static int fplus_sub(token_type *equation, int *np, int loc, int i1, int n1, int i2, int n2, int level, long v, double d, int whole_flag, int div_only);
static int big_fplus(token_type *equation, int level, int diff_sign, int sop1, int op1, int op2, int i1, int i2, int b1, int b2, int ai, int aj, int i, int j, int e1, int e2);
static int ftimes_recurse(token_type *equation, int *np, int loc, int level);
static int ftimes_sub(token_type *equation, int *np, int loc, int i1, int n1, int i2, int n2, int level);
static int fpower_recurse(token_type *equation, int *np, int loc, int level);
static int fpower_sub(token_type *equation, int *np, int loc, int i1, int n1, int i2, int n2, int level);
/*
* Factor divides only: (a/c + b/c) -> ((a+b)/c).
*
* Return true if equation side was modified.
*/
int
factor_divide(equation, np, v, d)
token_type *equation;
int *np;
long v;
double d;
{
return fplus_recurse(equation, np, 0, 1, v, d, false, true);
}
/*
* Take care of subtraction and addition of the same expression
* multiplied by constants: (2*a + 3*a - a) -> (4*a).
*
* Return true if equation side was modified.
*/
int
subtract_itself(equation, np)
token_type *equation;
int *np;
{
return fplus_recurse(equation, np, 0, 1, 0L, 0.0, true, false);
}
/*
* Factor equation side: (a*c + b*c) -> (c*(a + b)).
*
* If "v" and "d" equal 0, factor anything,
* including identical bases raised to powers (Horner factoring): (x^2 + x) -> (x*(x + 1)).
* If "d" equals 1.0, only factor identical bases raised to the power of a constant.
*
* If "v" is a variable, or MATCH_ANY, only factor expressions containing that variable,
* or any variable, respectively, with no Horner factoring.
* IF "v" is not MATCH_ANY, and "d" is not equal to 0.0 or 1.0,
* factor only expressions containing "v" raised to the power of "d".
*
* In order to factor down to the smallest possible expression,
* factoring the most common and largest sub-expressions needs to be done first.
* Mathomatic does not have the ability to do that.
* However, simpb_side() factors expressions with the most used variables first,
* which is helpful.
*
* Return true if equation side was modified.
*/
int
factor_plus(equation, np, v, d)
token_type *equation; /* pointer to beginning of equation side */
int *np; /* pointer to length of equation side */
long v; /* Mathomatic variable */
double d; /* control exponent */
{
return fplus_recurse(equation, np, 0, 1, v, d, false, false);
}
/*
* Recursively factor at "level" of parentheses and deeper,
* beginning at index "loc".
*
* Return true if equation side was modified.
*/
static int
fplus_recurse(equation, np, loc, level, v, d, whole_flag, div_only)
token_type *equation;
int *np, loc, level;
long v;
double d;
int whole_flag; /* factor only whole expressions multiplied by a constant */
int div_only; /* factor only divides */
{
int modified = false;
int i, j, k;
int op = 0;
int len1, len2;
for (i = loc + 1; i < *np && equation[i].level >= level; i += 2) {
if (equation[i].level == level) {
op = equation[i].token.operatr;
break;
}
}
switch (op) {
case PLUS:
case MINUS:
for (i = loc;;) {
f_again:
for (k = i + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len1 = k - i;
for (j = i + len1 + 1;; j += len2 + 1) {
if (j >= *np || equation[j-1].level < level)
break;
for (k = j + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len2 = k - j;
if (fplus_sub(equation, np, loc, i, len1, j, len2, level + 1, v, d, whole_flag, div_only)) {
modified = true;
goto f_again;
}
}
i += len1 + 1;
if (i >= *np || equation[i-1].level < level)
break;
}
}
if (modified)
return true;
for (i = loc; i < *np && equation[i].level >= level;) {
if (equation[i].level > level) {
modified |= fplus_recurse(equation, np, i, level + 1, v, d, whole_flag, div_only);
i++;
for (; i < *np && equation[i].level > level; i += 2)
;
continue;
}
i++;
}
return modified;
}
/*
* Do the factoring of two sub-expressions added together.
*
* Return true if a transformation was made.
*/
static int
fplus_sub(equation, np, loc, i1, n1, i2, n2, level, v, d, whole_flag, div_only)
token_type *equation; /* the entire expression */
int *np; /* pointer to length of the entire expression */
int loc; /* index into the beginning of this additive sub-expression */
int i1, n1, i2, n2;
int level;
long v;
double d;
int whole_flag; /* factor only whole expressions multiplied by a constant */
int div_only; /* factor only divides */
{
int e1, e2;
int op1, op2;
int i, j, k, l, m;
int b1, b2;
int len;
int sop1;
int diff_sign;
int ai, aj;
int flag1, flag2;
int same_flag;
double save_k1, save_k2;
double save_d1, save_d2;
double power; /* for constant power horner factoring */
double d1, d2;
e1 = i1 + n1;
e2 = i2 + n2;
op2 = equation[i2-1].token.operatr;
if (i1 <= loc) {
op1 = PLUS;
} else {
op1 = equation[i1-1].token.operatr;
}
i = i1 - 1;
f_outer:
b1 = i + 1;
if (b1 >= e1)
return false;
if (whole_flag) {
i = e1;
if (n1 > 1 && equation[b1].kind == CONSTANT
&& equation[b1+1].level == level
&& (equation[b1+1].token.operatr == TIMES
|| equation[b1+1].token.operatr == DIVIDE)) {
b1 += 2;
}
} else {
i = b1 + 1;
for (; i < e1; i += 2) {
if (equation[i].level == level
&& (equation[i].token.operatr == TIMES
|| equation[i].token.operatr == DIVIDE)) {
break;
}
}
}
if (b1 <= i1)
sop1 = TIMES;
else
sop1 = equation[b1-1].token.operatr;
if ((div_only && sop1 != DIVIDE)
|| (i - b1 == 1 && equation[b1].kind == CONSTANT && fabs(equation[b1].token.constant) == 1.0)) {
goto f_outer;
}
if (!whole_flag && (v != MATCH_ANY)) {
if (d == 0.0 || d == 1.0) {
if (v) {
for (k = b1;; k += 2) {
if (k >= i)
goto f_outer;
if (equation[k].kind == VARIABLE && equation[k].token.variable == v) {
break;
}
}
}
} else {
for (k = b1 + 1;; k += 2) {
if (k >= i)
goto f_outer;
if (equation[k].token.operatr == POWER
&& equation[k].level == equation[k+1].level
&& equation[k+1].kind == CONSTANT
&& equation[k+1].token.constant == d) {
if (v == 0)
goto factor_this;
for (l = k - 1; l >= 0; l--) {
if (equation[l].level < equation[k].level)
break;
if (equation[l].kind == VARIABLE
&& equation[l].token.variable == v)
goto factor_this;
}
}
}
}
}
factor_this:
j = i2 - 1;
f_inner:
b2 = j + 1;
if (b2 >= e2)
goto f_outer;
if (whole_flag) {
j = e2;
if (n2 > 1 && equation[b2].kind == CONSTANT
&& equation[b2+1].level == level
&& (equation[b2+1].token.operatr == TIMES
|| equation[b2+1].token.operatr == DIVIDE)) {
b2 += 2;
}
} else {
j = b2 + 1;
for (; j < e2; j += 2) {
if (equation[j].level == level
&& (equation[j].token.operatr == TIMES
|| equation[j].token.operatr == DIVIDE)) {
break;
}
}
if (b2 <= i2) {
if (sop1 == DIVIDE)
goto f_inner;
} else {
if (equation[b2-1].token.operatr != sop1)
goto f_inner;
}
}
if (j - b2 == 1 && equation[b2].kind == CONSTANT && fabs(equation[b2].token.constant) == 1.0) {
goto f_inner;
}
ai = i;
aj = j;
save_k1 = 0.0;
save_k2 = 0.0;
flag1 = (whole_flag && b1 > i1);
if (flag1) {
b1 = i1;
save_k1 = equation[b1].token.constant;
equation[b1].token.constant = 1.0;
}
flag2 = (whole_flag && b2 > i2);
if (flag2) {
b2 = i2;
save_k2 = equation[b2].token.constant;
equation[b2].token.constant = 1.0;
}
same_flag = se_compare(&equation[b1], i - b1, &equation[b2], j - b2, &diff_sign);
if (flag1) {
equation[i1].token.constant = save_k1;
b1 += 2;
}
if (flag2) {
equation[i2].token.constant = save_k2;
b2 += 2;
}
if (same_flag) {
/* do the factor transformation */
power = 1.0; /* not doing Horner factoring */
horner_factor:
if (sop1 == DIVIDE) {
scratch[0].level = level;
scratch[0].kind = CONSTANT;
scratch[0].token.constant = 1.0;
scratch[1].level = level;
scratch[1].kind = OPERATOR;
scratch[1].token.operatr = DIVIDE;
len = 2;
} else {
len = 0;
}
k = len;
blt(&scratch[len], &equation[b1], (ai - b1) * sizeof(token_type));
len += ai - b1;
if (power != 1.0) {
for (; k < len; k++)
scratch[k].level += 2;
scratch[len].level = level + 1;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = POWER;
len++;
scratch[len].level = level + 1;
scratch[len].kind = CONSTANT;
scratch[len].token.constant = power;
len++;
if (always_positive(power))
diff_sign = false;
} else if (b1 == i1 && ai == e1) {
for (; k < len; k++)
scratch[k].level++;
}
scratch[len].level = level;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = TIMES;
len++;
k = len;
blt(&scratch[len], &equation[i1], (b1 - i1) * sizeof(token_type));
len += b1 - i1;
if (ai != i) {
l = len;
m = len + ai - b1;
blt(&scratch[len], &equation[b1], (i - b1) * sizeof(token_type));
len += i - b1;
if (b1 == i1 && i == e1) {
for (; l < len; l++)
scratch[l].level++;
}
l = m;
m++;
for (; m < len; m++)
scratch[m].level++;
scratch[len].level = scratch[l].level + 1;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = MINUS;
len++;
scratch[len].level = scratch[l].level + 1;
scratch[len].kind = CONSTANT;
scratch[len].token.constant = power;
len++;
scratch[len].level = level;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = TIMES;
len++;
}
scratch[len].level = level;
scratch[len].kind = CONSTANT;
if (op1 == MINUS) {
scratch[len].token.constant = -1.0;
} else {
scratch[len].token.constant = 1.0;
}
len++;
blt(&scratch[len], &equation[i], (e1 - i) * sizeof(token_type));
len += e1 - i;
for (; k < len; k++)
scratch[k].level += 2;
scratch[len].level = level + 1;
scratch[len].kind = OPERATOR;
diff_sign ^= (op2 == MINUS);
if (diff_sign) {
scratch[len].token.operatr = MINUS;
} else {
scratch[len].token.operatr = PLUS;
}
len++;
k = len;
if (aj != j) {
if (len + n2 + 2 > n_tokens) {
error_huge();
}
} else {
if (len + (b2 - i2) + (e2 - j) + 1 > n_tokens) {
error_huge();
}
}
blt(&scratch[len], &equation[i2], (b2 - i2) * sizeof(token_type));
len += b2 - i2;
if (aj != j) {
m = len + aj - b2;
blt(&scratch[len], &equation[b2], (j - b2) * sizeof(token_type));
len += j - b2;
l = m;
m++;
for (; m < len; m++)
scratch[m].level++;
scratch[len].level = scratch[l].level + 1;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = MINUS;
len++;
scratch[len].level = scratch[l].level + 1;
scratch[len].kind = CONSTANT;
scratch[len].token.constant = power;
len++;
} else {
scratch[len].level = level;
scratch[len].kind = CONSTANT;
scratch[len].token.constant = 1.0;
len++;
}
blt(&scratch[len], &equation[j], (e2 - j) * sizeof(token_type));
len += e2 - j;
for (; k < len; k++)
scratch[k].level += 2;
end_mess:
if (*np + len - n1 - (n2 + 1) > n_tokens) {
error_huge();
}
if (op1 == MINUS) {
equation[i1-1].token.operatr = PLUS;
}
blt(&equation[i2-1], &equation[e2], (*np - e2) * sizeof(token_type));
*np -= n2 + 1;
blt(&equation[i1+len], &equation[e1], (*np - e1) * sizeof(token_type));
*np += len - n1;
blt(&equation[i1], scratch, len * sizeof(token_type));
return true;
}
if (whole_flag)
return false;
if (v || div_only)
goto f_inner; /* don't do Horner factoring */
if (b1 == i1 && i == e1)
k = level;
else
k = level + 1;
save_d1 = 1.0;
for (l = b1 + 1;; l += 2) {
if (l >= i) {
break;
}
if (equation[l].level == k && equation[l].token.operatr == POWER) {
if (equation[l+1].level == k && equation[l+1].kind == CONSTANT) {
save_d1 = equation[l+1].token.constant;
if (save_d1 <= 0.0)
goto f_inner;
} else {
save_d1 = -1.0;
}
ai = l;
break;
}
}
if (b2 == i2 && j == e2)
k = level;
else
k = level + 1;
save_d2 = 1.0;
for (l = b2 + 1;; l += 2) {
if (l >= j) {
break;
}
if (equation[l].level == k && equation[l].token.operatr == POWER) {
if (equation[l+1].level == k && equation[l+1].kind == CONSTANT) {
save_d2 = equation[l+1].token.constant;
if (save_d2 <= 0.0)
goto f_inner;
} else {
save_d2 = -1.0;
}
aj = l;
break;
}
}
if (ai == i && aj == j)
goto f_inner;
if (ai - b1 == 1 && equation[b1].kind == CONSTANT)
goto f_inner;
if (d == 1.0 && (save_d1 < 0.0 || save_d2 < 0.0))
goto f_inner;
if (se_compare(&equation[b1], ai - b1, &equation[b2], aj - b2, &diff_sign)) {
if (save_d1 > 0.0 || save_d2 > 0.0) {
if (save_d1 < 0.0) {
power = save_d2;
} else if (save_d2 < 0.0) {
power = save_d1;
} else {
power = min(save_d1, save_d2);
if (!diff_sign && (fmod(power, 1.0) != 0.0)) {
if (fmod(max(save_d1, save_d2) - power, 1.0) == 0.0) {
goto horner_factor;
}
}
}
if (power < 1.0)
goto f_inner;
modf(power, &power); /* same as power = trunc(power); ? */
goto horner_factor;
}
d1 = i - ai;
d2 = j - aj;
if (d1 == d2) {
d1 = 1.0;
d2 = 1.0;
if ((ai + 2) < i) {
k = equation[ai].level;
if (equation[ai+1].level == (k + 1)
&& equation[ai+2].level == (k + 1)
&& equation[ai+1].kind == CONSTANT
&& (equation[ai+2].token.operatr == TIMES
|| equation[ai+2].token.operatr == DIVIDE)) {
d1 = fabs(equation[ai+1].token.constant);
}
}
if ((aj + 2) < j) {
k = equation[aj].level;
if (equation[aj+1].level == (k + 1)
&& equation[aj+2].level == (k + 1)
&& equation[aj+1].kind == CONSTANT
&& (equation[aj+2].token.operatr == TIMES
|| equation[aj+2].token.operatr == DIVIDE)) {
d2 = fabs(equation[aj+1].token.constant);
}
}
}
if (d1 <= d2) {
len = big_fplus(equation, level, diff_sign, sop1,
op1, op2, i1, i2, b1, b2, ai, aj, i, j, e1, e2);
} else {
len = big_fplus(equation, level, diff_sign, sop1,
op2, op1, i2, i1, b2, b1, aj, ai, j, i, e2, e1);
}
goto end_mess;
}
goto f_inner;
}
/*
* Factor transformation for a more general pair of sub-expressions added together
* with a common base and any exponent.
*/
static int
big_fplus(equation, level, diff_sign, sop1, op1, op2, i1, i2, b1, b2, ai, aj, i, j, e1, e2)
token_type *equation;
int level;
int diff_sign;
int sop1;
int op1, op2;
int i1, i2;
int b1, b2;
int ai, aj;
int i, j;
int e1, e2;
{
int k, l, m, n, o;
int len;
if (sop1 == DIVIDE) {
scratch[0].level = level;
scratch[0].kind = CONSTANT;
scratch[0].token.constant = 1.0;
scratch[1].level = level;
scratch[1].kind = OPERATOR;
scratch[1].token.operatr = DIVIDE;
len = 2;
} else {
len = 0;
}
k = len;
o = len + ai - b1;
blt(&scratch[len], &equation[b1], (i - b1) * sizeof(token_type));
len += i - b1;
if (b1 == i1 && i == e1) {
for (; k < len; k++)
scratch[k].level++;
}
scratch[len].level = level;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = TIMES;
len++;
k = len;
blt(&scratch[len], &equation[i1], (b1 - i1) * sizeof(token_type));
len += b1 - i1;
scratch[len].level = level;
scratch[len].kind = CONSTANT;
if (op1 == MINUS) {
scratch[len].token.constant = -1.0;
} else {
scratch[len].token.constant = 1.0;
}
len++;
blt(&scratch[len], &equation[i], (e1 - i) * sizeof(token_type));
len += e1 - i;
for (; k < len; k++)
scratch[k].level += 2;
scratch[len].level = level + 1;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = op2;
len++;
k = len;
blt(&scratch[len], &equation[i2], (b2 - i2) * sizeof(token_type));
len += b2 - i2;
if (len + (e2 - b2) + 2 * (i - ai) + 2 > n_tokens) {
error_huge();
}
n = len;
m = len + aj - b2;
blt(&scratch[len], &equation[b2], (j - b2) * sizeof(token_type));
len += j - b2;
l = m;
m++;
for (; m < len; m++)
scratch[m].level++;
if (diff_sign && b2 == i2 && j == e2) {
for (; n < len; n++)
scratch[n].level++;
}
scratch[len].level = scratch[l].level + 1;
scratch[len].kind = OPERATOR;
scratch[len].token.operatr = MINUS;
len++;
m = len;
blt(&scratch[len], &equation[ai+1], (i - (ai + 1)) * sizeof(token_type));
len += i - (ai + 1);
n = min_level(&equation[ai+1], i - (ai + 1));
n = scratch[l].level + 2 - n;
for (; m < len; m++)
scratch[m].level += n;
if (diff_sign) {
scratch[len].level = level;
scratch[len].kind = OPERATOR;
if (sop1 == DIVIDE)
scratch[len].token.operatr = TIMES;
else
scratch[len].token.operatr = DIVIDE;
len++;
scratch[len].level = level + 1;
scratch[len].kind = CONSTANT;
scratch[len].token.constant = -1.0;
len++;
blt(&scratch[len], &scratch[o], (i - ai) * sizeof(token_type));
len += i - ai;
}
blt(&scratch[len], &equation[j], (e2 - j) * sizeof(token_type));
len += e2 - j;
for (; k < len; k++)
scratch[k].level += 2;
return len;
}
/*
* Factor equation side.
* a^b * a^c -> a^(b + c).
* Return true if equation side was modified.
*/
int
factor_times(equation, np)
token_type *equation;
int *np;
{
return ftimes_recurse(equation, np, 0, 1);
}
static int
ftimes_recurse(equation, np, loc, level)
token_type *equation;
int *np, loc, level;
{
int modified = false;
int i, j, k;
int op = 0;
int len1, len2;
for (i = loc + 1; i < *np && equation[i].level >= level; i += 2) {
if (equation[i].level == level) {
op = equation[i].token.operatr;
break;
}
}
switch (op) {
case TIMES:
case DIVIDE:
for (i = loc;;) {
f_again:
for (k = i + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len1 = k - i;
for (j = i + len1 + 1;; j += len2 + 1) {
if (j >= *np || equation[j-1].level < level)
break;
for (k = j + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len2 = k - j;
if (ftimes_sub(equation, np, loc, i, len1, j, len2, level + 1)) {
modified = true;
goto f_again;
}
}
i += len1 + 1;
if (i >= *np || equation[i-1].level < level)
break;
}
}
if (modified)
return true;
for (i = loc; i < *np && equation[i].level >= level;) {
if (equation[i].level > level) {
modified |= ftimes_recurse(equation, np, i, level + 1);
i++;
for (; i < *np && equation[i].level > level; i += 2)
;
continue;
}
i++;
}
return modified;
}
static int
ftimes_sub(equation, np, loc, i1, n1, i2, n2, level)
token_type *equation;
int *np, loc, i1, n1, i2, n2, level;
{
int e1, e2;
int op1, op2;
int i, j, k;
int len, rlen1, len2;
int diff_sign;
int both_divide;
e1 = i1 + n1;
e2 = i2 + n2;
op2 = equation[i2-1].token.operatr;
if (i1 <= loc) {
op1 = TIMES;
} else {
op1 = equation[i1-1].token.operatr;
}
#if 1
if ((n1 == 1 && equation[i1].kind == CONSTANT) && (n2 == 1 && equation[i2].kind == CONSTANT)) {
return false;
}
#else
if ((n1 == 1 && equation[i1].kind == CONSTANT) || (n2 == 1 && equation[i2].kind == CONSTANT)) {
return false;
}
#endif
both_divide = (op1 == DIVIDE && op2 == DIVIDE);
if (se_compare(&equation[i1], n1, &equation[i2], n2, &diff_sign)) {
i = e1;
j = e2;
goto common_base;
}
for (i = i1 + 1; i < e1; i += 2) {
if (equation[i].level == level && equation[i].token.operatr == POWER) {
break;
}
}
for (j = i2 + 1; j < e2; j += 2) {
if (equation[j].level == level && equation[j].token.operatr == POWER) {
break;
}
}
if (i >= e1 && j >= e2) {
return false;
}
if (se_compare(&equation[i1], i - i1, &equation[i2], j - i2, &diff_sign)) {
goto common_base;
}
if (i < e1 && j < e2) {
if (se_compare(&equation[i1], n1, &equation[i2], j - i2, &diff_sign)) {
i = e1;
goto common_base;
}
if (se_compare(&equation[i1], i - i1, &equation[i2], n2, &diff_sign)) {
j = e2;
goto common_base;
}
}
return false;
common_base:
rlen1 = ((i == e1) ? 1 : (e1 - i - 1));
len = (i - i1) + 1 + ((op1 == DIVIDE && !both_divide) ? 2 : 0) + rlen1 + 1
+ ((j == e2) ? 1 : (e2 - j - 1));
len -= n1;
if (j - i2 == 1 && equation[i2].kind == CONSTANT && equation[i2].token.constant == -1.0)
return false;
if (diff_sign) {
if (j - i2 == 1 && equation[i2].kind == CONSTANT)
return false;
len2 = 2 + e2 - j;
if (*np + len2 + len > n_tokens) {
error_huge();
}
blt(&equation[e2+len2], &equation[e2], (*np - e2) * sizeof(token_type));
*np += len2;
equation[e2].level = level - 1;
equation[e2].kind = OPERATOR;
equation[e2].token.operatr = op2;
equation[e2+1].level = level;
equation[e2+1].kind = CONSTANT;
equation[e2+1].token.constant = -1.0;
blt(&equation[e2+2], &equation[j], (e2 - j) * sizeof(token_type));
}
if (*np + len > n_tokens) {
error_huge();
}
blt(&equation[e1+len], &equation[e1], (*np - e1) * sizeof(token_type));
*np += len;
if (i == e1) {
for (k = i1; k < e1; k++)
equation[k].level++;
equation[i].level = level;
equation[i].kind = OPERATOR;
equation[i].token.operatr = POWER;
equation[i+1].level = level;
equation[i+1].kind = CONSTANT;
equation[i+1].token.constant = 1.0;
}
if (op1 == DIVIDE && !both_divide) {
equation[i1-1].token.operatr = TIMES;
blt(&equation[i+3], &equation[i+1], rlen1 * sizeof(token_type));
i++;
equation[i].level = level;
equation[i].kind = CONSTANT;
equation[i].token.constant = -1.0;
i++;
equation[i].level = level;
equation[i].kind = OPERATOR;
equation[i].token.operatr = TIMES;
binary_parenthesize(equation, i + 1 + rlen1, i);
}
i += rlen1 + 1;
equation[i].level = level;
equation[i].kind = OPERATOR;
if (op2 == DIVIDE && !both_divide)
equation[i].token.operatr = MINUS;
else
equation[i].token.operatr = PLUS;
if (j == e2) {
equation[i+1].level = level;
equation[i+1].kind = CONSTANT;
equation[i+1].token.constant = 1.0;
binary_parenthesize(equation, i + 2, i);
} else {
blt(&equation[i+1], &equation[j+len+1], (e2 - j - 1) * sizeof(token_type));
binary_parenthesize(equation, i + e2 - j, i);
}
blt(&equation[i2+len-1], &equation[e2+len], (*np - (e2 + len)) * sizeof(token_type));
*np -= n2 + 1;
return true;
}
/*
* Factor equation side.
* a^c * b^c -> (a * b)^c.
* Return true if equation side was modified.
*/
int
factor_power(equation, np)
token_type *equation;
int *np;
{
return fpower_recurse(equation, np, 0, 1);
}
static int
fpower_recurse(equation, np, loc, level)
token_type *equation;
int *np, loc, level;
{
int modified = false;
int i, j, k;
int op = 0;
int len1, len2;
for (i = loc + 1; i < *np && equation[i].level >= level; i += 2) {
if (equation[i].level == level) {
op = equation[i].token.operatr;
break;
}
}
switch (op) {
case TIMES:
case DIVIDE:
for (i = loc;;) {
f_again:
for (k = i + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len1 = k - i;
for (j = i + len1 + 1;; j += len2 + 1) {
if (j >= *np || equation[j-1].level < level)
break;
for (k = j + 1;; k += 2) {
if (k >= *np || equation[k].level <= level)
break;
}
len2 = k - j;
if (fpower_sub(equation, np, loc, i, len1, j, len2, level + 1)) {
modified = true;
goto f_again;
}
}
i += len1 + 1;
if (i >= *np || equation[i-1].level < level)
break;
}
}
for (i = loc; i < *np && equation[i].level >= level;) {
if (equation[i].level > level) {
modified |= fpower_recurse(equation, np, i, level + 1);
i++;
for (; i < *np && equation[i].level > level; i += 2)
;
continue;
}
i++;
}
return modified;
}
static int
fpower_sub(equation, np, loc, i1, n1, i2, n2, level)
token_type *equation;
int *np, loc, i1, n1, i2, n2, level;
{
int e1, e2;
int op1, op2;
int pop1 = TIMES;
int start2;
int i, j, k;
int b1, b2;
int len;
int diff_sign;
int all_divide;
#if !ALWAYS_FACTOR_POWER
int abs1_flag = false, abs2_flag = false;
#endif
e1 = i1 + n1;
e2 = i2 + n2;
op2 = equation[i2-1].token.operatr;
if (i1 <= loc) {
op1 = TIMES;
} else {
op1 = equation[i1-1].token.operatr;
}
for (i = i1 + 1;; i += 2) {
if (i >= e1)
return false;
if (equation[i].level == level && equation[i].token.operatr == POWER) {
#if !ALWAYS_FACTOR_POWER
/* avoid absolute values: */