eigenmath/arccos.cpp

166 lines
1.9 KiB
C++

#include "stdafx.h"
#include "defs.h"
void
eval_arccos(void)
{
push(cadr(p1));
eval();
arccos();
}
void
arccos(void)
{
int n;
double d;
save();
p1 = pop();
if (car(p1) == symbol(COS)) {
push(cadr(p1));
restore();
return;
}
if (isdouble(p1)) {
errno = 0;
d = acos(p1->u.d);
if (errno)
stop("arccos function argument is not in the interval [-1,1]");
push_double(d);
restore();
return;
}
// if p1 == 1/sqrt(2) then return 1/4*pi (45 degrees)
if (isoneoversqrttwo(p1)) {
push_rational(1, 4);
push_symbol(PI);
multiply();
restore();
return;
}
// if p1 == -1/sqrt(2) then return 3/4*pi (135 degrees)
if (isminusoneoversqrttwo(p1)) {
push_rational(3, 4);
push_symbol(PI);
multiply();
restore();
return;
}
if (!isrational(p1)) {
push_symbol(ARCCOS);
push(p1);
list(2);
restore();
return;
}
push(p1);
push_integer(2);
multiply();
n = pop_integer();
switch (n) {
case -2:
push_symbol(PI);
break;
case -1:
push_rational(2, 3);
push_symbol(PI);
multiply();
break;
case 0:
push_rational(1, 2);
push_symbol(PI);
multiply();
break;
case 1:
push_rational(1, 3);
push_symbol(PI);
multiply();
break;
case 2:
push(zero);
break;
default:
push_symbol(ARCCOS);
push(p1);
list(2);
break;
}
restore();
}
#if SELFTEST
static char *s[] = {
"arccos(1)",
"0",
"arccos(1/2)",
"1/3*pi",
"arccos(0)",
"1/2*pi",
"arccos(-1/2)",
"2/3*pi",
"arccos(-1)",
"pi",
"arccos(cos(0))",
"0",
"arccos(cos(1/3*pi))",
"1/3*pi",
"arccos(cos(1/2*pi))",
"1/2*pi",
"arccos(cos(2/3*pi))",
"2/3*pi",
"arccos(cos(pi))",
"pi",
"arccos(cos(x))",
"x",
"arccos(1/sqrt(2))",
"1/4*pi",
"arccos(-1/sqrt(2))",
"3/4*pi",
"arccos(cos(1/4*pi))",
"1/4*pi",
"arccos(cos(3/4*pi))",
"3/4*pi",
};
void
test_arccos(void)
{
test(__FILE__, s, sizeof s / sizeof (char *));
}
#endif