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/* vi: set sw=4 ts=4: */
#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 ...\n\n"
"This is a Tiny RPN calculator that understands the\n"
"following operations: +, -, /, *, and, or, not, eor.\n"
"i.e. 'math 2 2 add' -> 4, and 'math 8 8 \\* 2 2 + /' -> 16\n";
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},
{"-", sub},
{"*", mul},
{"/", divide},
{"and", and},
{"or", or},
{"not", not},
{"eor", eor},
{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)
{
if (argc < 1 || *argv[1]=='-')
usage(math_usage);
while (argc >= 2) {
stack_machine(argv[1]);
argv++;
argc--;
}
stack_machine(0);
exit( TRUE);
}
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