96 lines
1.1 KiB
C++
96 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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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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yylog();
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restore();
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}
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void
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yylog(void)
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{
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double d;
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p1 = pop();
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if (p1 == symbol(E)) {
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push_integer(1);
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return;
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}
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if (equaln(p1, 1)) {
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push_integer(0);
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return;
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}
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if (isnegativenumber(p1)) {
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push(p1);
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negate();
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logarithm();
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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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return;
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}
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if (isdouble(p1)) {
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d = log(p1->u.d);
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push_double(d);
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return;
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}
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// rational number and not an integer?
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if (isfraction(p1)) {
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push(p1);
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numerator();
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logarithm();
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push(p1);
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denominator();
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logarithm();
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subtract();
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return;
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}
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// log(a ^ b) --> b log(a)
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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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// log(a * b) --> log(a) + log(b)
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if (car(p1) == symbol(MULTIPLY)) {
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push_integer(0);
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p1 = cdr(p1);
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while (iscons(p1)) {
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push(car(p1));
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logarithm();
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add();
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p1 = cdr(p1);
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}
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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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} |