110 lines
1.6 KiB
C++
110 lines
1.6 KiB
C++
// Condense an expression by factoring common terms.
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#include "stdafx.h"
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#include "defs.h"
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void
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eval_condense(void)
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{
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push(cadr(p1));
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eval();
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Condense();
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}
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void
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Condense(void)
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{
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int tmp;
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tmp = expanding;
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save();
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yycondense();
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restore();
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expanding = tmp;
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}
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void
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yycondense(void)
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{
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expanding = 0;
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p1 = pop();
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if (car(p1) != symbol(ADD)) {
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push(p1);
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return;
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}
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// get gcd of all terms
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p3 = cdr(p1);
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push(car(p3));
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p3 = cdr(p3);
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while (iscons(p3)) {
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push(car(p3));
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gcd();
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p3 = cdr(p3);
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}
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//printf("condense: this is the gcd of all the terms:\n");
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//print(stdout, stack[tos - 1]);
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// divide each term by gcd
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inverse();
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p2 = pop();
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push(zero);
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p3 = cdr(p1);
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while (iscons(p3)) {
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push(p2);
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push(car(p3));
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multiply();
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add();
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p3 = cdr(p3);
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}
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// We multiplied above w/o expanding so sum factors cancelled.
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// Now we expand which which normalizes the result and, in some cases,
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// simplifies it too (see test case H).
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yyexpand();
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// multiply result by gcd
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push(p2);
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divide();
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}
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#if SELFTEST
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static char *s[] = {
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"condense(a/(a+b)+b/(a+b))",
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"1",
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"psi(n) = exp(-r/n) laguerre(2r/n,n-1,1)",
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"",
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"psi(3)",
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"3*exp(-1/3*r)-2*r*exp(-1/3*r)+2/9*r^2*exp(-1/3*r)",
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"condense(last)",
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"exp(-1/3*r)*(3-2*r+2/9*r^2)",
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"psi()=psi",
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"",
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// test case H
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"condense(-3 exp(-1/3 r + i phi) cos(theta) - 6 exp(-1/3 r + i phi) cos(theta) sin(theta)^2 + 12 exp(-1/3 r + i phi) cos(theta)^3)",
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"3*exp(-1/3*r+i*phi)*(-1+4*cos(theta)^2-2*sin(theta)^2)*cos(theta)",
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};
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void
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test_condense(void)
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{
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test(__FILE__, s, sizeof s / sizeof (char *));
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}
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#endif
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