143 lines
1.8 KiB
C++
143 lines
1.8 KiB
C++
#include "stdafx.h"
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#include "defs.h"
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void
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eval_arctan(void)
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{
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push(cadr(p1));
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eval();
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arctan();
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}
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void
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arctan(void)
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{
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double d;
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save();
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p1 = pop();
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if (car(p1) == symbol(TAN)) {
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push(cadr(p1));
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restore();
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return;
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}
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if (isdouble(p1)) {
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errno = 0;
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d = atan(p1->u.d);
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if (errno)
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stop("arctan function error");
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push_double(d);
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restore();
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return;
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}
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if (iszero(p1)) {
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push(zero);
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restore();
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return;
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}
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if (isnegative(p1)) {
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push(p1);
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negate();
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arctan();
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negate();
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restore();
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return;
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}
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// arctan(sin(a) / cos(a)) ?
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if (find(p1, symbol(SIN)) && find(p1, symbol(COS))) {
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push(p1);
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numerator();
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p2 = pop();
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push(p1);
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denominator();
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p3 = pop();
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if (car(p2) == symbol(SIN) && car(p3) == symbol(COS) && equal(cadr(p2), cadr(p3))) {
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push(cadr(p2));
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restore();
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return;
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}
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}
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// arctan(1/sqrt(3)) -> pi/6
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if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), -1, 2)) {
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push_rational(1, 6);
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push(symbol(PI));
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multiply();
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restore();
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return;
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}
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// arctan(1) -> pi/4
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if (equaln(p1, 1)) {
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push_rational(1, 4);
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push(symbol(PI));
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multiply();
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restore();
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return;
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}
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// arctan(sqrt(3)) -> pi/3
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if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), 1, 2)) {
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push_rational(1, 3);
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push(symbol(PI));
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multiply();
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restore();
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return;
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}
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push_symbol(ARCTAN);
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push(p1);
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list(2);
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restore();
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}
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static char *s[] = {
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"arctan(x)",
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"arctan(x)",
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"arctan(-x)",
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"-arctan(x)",
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"arctan(0)",
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"0",
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"arctan(tan(x))",
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"x",
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"arctan(1/sqrt(3))-pi/6", // 30 degrees
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"0",
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"arctan(1)-pi/4", // 45 degrees
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"0",
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"arctan(sqrt(3))-pi/3", // 60 degrees
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"0",
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"arctan(a-b)",
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"arctan(a-b)",
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"arctan(b-a)",
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"-arctan(a-b)",
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"arctan(tan(x))",
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"x",
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};
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void
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test_arctan(void)
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{
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test(__FILE__, s, sizeof s / sizeof (char *));
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}
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