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#include "internal.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
/* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
static const char math_usage[] = "math expression ...";
static double stack[100];
static unsigned int pointer;
static void
push(double a)
{
if ( pointer >= (sizeof(stack) / sizeof(*stack)) ) {
fprintf(stderr, "math: stack overflow\n");
exit(-1);
}
else
stack[pointer++] = a;
}
static double
pop()
{
if ( pointer == 0 ) {
fprintf(stderr, "math: stack underflow\n");
exit(-1);
}
return stack[--pointer];
}
static void
add()
{
push(pop() + pop());
}
static void
sub()
{
double subtrahend = pop();
push(pop() - subtrahend);
}
static void
mul()
{
push(pop() * pop());
}
static void
divide()
{
double divisor = pop();
push(pop() / divisor);
}
static void
and()
{
push((unsigned int)pop() & (unsigned int)pop());
}
static void
or()
{
push((unsigned int)pop() | (unsigned int)pop());
}
static void
eor()
{
push((unsigned int)pop() ^ (unsigned int)pop());
}
static void
not()
{
push(~(unsigned int)pop());
}
static void
print()
{
printf("%g\n", pop());
}
struct op {
const char * name;
void (*function)();
};
static const struct op operators[] = {
{ "add", add },
{ "and", and },
{ "div", divide },
{ "eor", eor },
{ "mul", mul },
{ "not", not },
{ "or", or },
{ "sub", sub },
{ 0, 0 }
};
static void
stack_machine(const char * argument)
{
char * endPointer = 0;
double d;
const struct op * o = operators;
if ( argument == 0 ) {
print();
return;
}
d = strtod(argument, &endPointer);
if ( endPointer != argument ) {
push(d);
return;
}
while ( o->name != 0 ) {
if ( strcmp(o->name, argument) == 0 ) {
(*(o->function))();
return;
}
o++;
}
fprintf(stderr, "math: %s: syntax error.\n", argument);
exit(-1);
}
int
math_main(int argc, char * * argv)
{
while ( argc >= 2 ) {
stack_machine(argv[1]);
argv++;
argc--;
}
stack_machine(0);
return 0;
}
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