183 lines
2.1 KiB
C++
183 lines
2.1 KiB
C++
// Do the cosine function.
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#include "stdafx.h"
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#include "defs.h"
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static void cosine_f(void);
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void
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eval_cos(void)
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{
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push(cadr(p1));
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eval();
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cosine();
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}
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void
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cosine(void)
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{
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save();
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cosine_f();
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restore();
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}
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static void
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cosine_f(void)
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{
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int n;
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double d;
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p1 = pop();
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if (p1->k == DOUBLE) {
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d = cos(p1->u.d);
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if (fabs(d) < 1e-10)
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d = 0.0;
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push_double(d);
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return;
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}
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if (expomode == 1) {
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push(p1);
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expcos();
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return;
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}
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// cosine function is symmetric, cos(-x) = cos(x)
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if (isnegative(p1)) {
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push(p1);
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negate();
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p1 = pop();
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}
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// multiply by 180/pi
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push(p1);
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push_integer(180);
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multiply();
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push_symbol(PI);
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divide();
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n = pop_integer();
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if (n < 0) {
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push_symbol(COS);
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push(p1);
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list(2);
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return;
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}
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switch (n % 360) {
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case 0:
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push_integer(1);
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break;
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case 60:
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push_rational(1, 2);
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break;
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case 90:
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push_integer(0);
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break;
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case 120:
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push_rational(-1, 2);
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break;
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case 180:
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push_integer(-1);
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break;
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case 240:
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push_rational(-1, 2);
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break;
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case 270:
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push_integer(0);
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break;
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case 300:
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push_rational(1, 2);
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break;
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default:
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push_symbol(COS);
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push(p1);
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list(2);
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break;
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}
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}
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static char *s[] = {
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"expomode=0",
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"",
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"cos(-pi)", // -180 degrees
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"-1",
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"cos(-5/6*pi)", // -150 degrees
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"cos(5/6*pi)",
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"cos(-3/4*pi)", // -135 degrees
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"cos(3/4*pi)",
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"cos(-pi*2/3)", // -120 degrees
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"-1/2",
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"cos(-pi/2)", // -90 degrees
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"0",
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"cos(-pi/3)", // -60 degrees
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"1/2",
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"cos(-1/4*pi)", // -45 degrees
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"cos(1/4*pi)",
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"cos(-1/6*pi)", // -30 degrees
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"cos(1/6*pi)",
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"cos(0)", // 0 degrees
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"1",
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"cos(1/6*pi)", // 30 degrees
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"cos(1/6*pi)",
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"cos(1/4*pi)", // 45 degrees
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"cos(1/4*pi)",
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"cos(pi/3)", // 60 degrees
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"1/2",
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"cos(pi/2)", // 90 degrees
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"0",
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"cos(pi*2/3)", // 120 degrees
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"-1/2",
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"cos(3/4*pi)", // 135 degrees
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"cos(3/4*pi)",
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"cos(5/6*pi)", // 150 degrees
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"cos(5/6*pi)",
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"cos(pi)", // 180 degrees
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"-1",
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"expomode=1",
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"",
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"cos(x)",
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"1/2*exp(-i*x)+1/2*exp(i*x)",
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"expomode=0",
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"",
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// cosine function is symmetric
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"cos(-x)",
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"cos(x)",
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"cos(b-a)",
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"cos(a-b)",
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};
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void
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test_cos(void)
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{
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test(__FILE__, s, sizeof s / sizeof (char *));
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}
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