eigenmath/distill.cpp

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1.7 KiB
C++
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2004-03-03 21:24:06 +01:00
#include "stdafx.h"
#include "defs.h"
static void _distill(void);
// take expr and push all constant subexpr
// p1 expr
// p2 independent variable (like x)
void
distill(void)
{
save();
_distill();
restore();
}
static void
_distill(void)
{
p2 = pop();
p1 = pop();
// is the entire expression constant?
if (find(p1, p2) == 0) {
push(p1);
//push(p1); // may need later for pushing both +a, -a
//negate();
return;
}
// sum?
if (isadd(p1)) {
distill_sum();
return;
}
// product?
if (car(p1) == symbol(MULTIPLY)) {
distill_product();
return;
}
// naive distill if not sum or product
p3 = cdr(p1);
while (iscons(p3)) {
push(car(p3));
push(p2);
distill();
p3 = cdr(p3);
}
}
void
distill_sum(void)
{
int h;
// distill terms involving x
p3 = cdr(p1);
while (iscons(p3)) {
if (find(car(p3), p2)) {
push(car(p3));
push(p2);
distill();
}
p3 = cdr(p3);
}
// add together all constant terms
h = tos;
p3 = cdr(p1);
while (iscons(p3)) {
if (find(car(p3), p2) == 0)
push(car(p3));
p3 = cdr(p3);
}
if (tos - h) {
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add_all(tos - h);
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p3 = pop();
push(p3);
push(p3);
negate(); // need both +a, -a for some integrals
}
}
void
distill_product(void)
{
int h;
// distill factors involving x
p3 = cdr(p1);
while (iscons(p3)) {
if (find(car(p3), p2)) {
push(car(p3));
push(p2);
distill();
}
p3 = cdr(p3);
}
// multiply together all constant factors
h = tos;
p3 = cdr(p1);
while (iscons(p3)) {
if (find(car(p3), p2) == 0)
push(car(p3));
p3 = cdr(p3);
}
if (tos - h) {
multiply_all(tos - h);
//p3 = pop(); // may need later for pushing both +a, -a
//push(p3);
//push(p3);
//negate();
}
}