107 lines
1.1 KiB
C++
107 lines
1.1 KiB
C++
// natural logarithm
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#include "stdafx.h"
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#include "defs.h"
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static void ylog(void);
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void
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eval_log(void)
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{
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push(cadr(p1));
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eval();
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logarithm();
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}
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void
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logarithm(void)
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{
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save();
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ylog();
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restore();
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}
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static void
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ylog(void)
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{
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double d;
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p1 = pop();
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if (isdouble(p1)) {
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d = p1->u.d;
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if (d < 0.0) {
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d = log(-d);
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push_double(d);
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push(imaginaryunit);
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push_symbol(PI);
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multiply();
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add();
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} else {
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d = log(d);
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push_double(d);
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}
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return;
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}
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if (equal(p1, one)) {
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push_integer(0);
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return;
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}
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if (p1 == symbol(E)) {
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push(one);
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return;
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}
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if (car(p1) == symbol(POWER)) {
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push(caddr(p1));
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push(cadr(p1));
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logarithm();
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multiply();
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return;
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}
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push_symbol(LOG);
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push(p1);
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list(2);
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}
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static char *s[] = {
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"log(1)",
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"0",
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"log(exp(1))",
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"1",
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"log(exp(x))",
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"x",
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"exp(log(x))",
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"x",
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"log(x^2)",
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"2*log(x)",
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"log(1/x)",
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"-log(x)",
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"log(a^b)",
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"b*log(a)",
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"log(2)",
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"log(2)",
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"log(2.0)",
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"0.693147",
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"float(log(2))",
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"0.693147",
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};
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void
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test_log(void)
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{
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test(__FILE__, s, sizeof s / sizeof (char *));
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}
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