143 lines
2.2 KiB
C
143 lines
2.2 KiB
C
/* vi: set sw=4 ts=4: */
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#include "internal.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <math.h>
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/* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
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static const char math_usage[] = "math expression ...\n\n"
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"This is a Tiny RPN calculator that understands the\n"
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"following operations: +, -, /, *, and, or, not, eor.\n"
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"i.e. 'math 2 2 add' -> 4, and 'math 8 8 \\* 2 2 + /' -> 16\n";
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static double stack[100];
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static unsigned int pointer;
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static void push(double a)
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{
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if (pointer >= (sizeof(stack) / sizeof(*stack))) {
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fprintf(stderr, "math: stack overflow\n");
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exit(-1);
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} else
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stack[pointer++] = a;
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}
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static double pop()
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{
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if (pointer == 0) {
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fprintf(stderr, "math: stack underflow\n");
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exit(-1);
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}
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return stack[--pointer];
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}
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static void add()
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{
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push(pop() + pop());
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}
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static void sub()
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{
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double subtrahend = pop();
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push(pop() - subtrahend);
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}
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static void mul()
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{
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push(pop() * pop());
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}
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static void divide()
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{
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double divisor = pop();
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push(pop() / divisor);
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}
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static void and()
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{
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push((unsigned int) pop() & (unsigned int) pop());
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}
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static void or()
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{
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push((unsigned int) pop() | (unsigned int) pop());
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}
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static void eor()
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{
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push((unsigned int) pop() ^ (unsigned int) pop());
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}
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static void not()
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{
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push(~(unsigned int) pop());
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}
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static void print()
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{
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printf("%g\n", pop());
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}
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struct op {
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const char *name;
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void (*function) ();
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};
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static const struct op operators[] = {
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{"+", add},
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{"-", sub},
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{"*", mul},
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{"/", divide},
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{"and", and},
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{"or", or},
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{"not", not},
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{"eor", eor},
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{0, 0}
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};
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static void stack_machine(const char *argument)
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{
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char *endPointer = 0;
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double d;
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const struct op *o = operators;
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if (argument == 0) {
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print();
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return;
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}
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d = strtod(argument, &endPointer);
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if (endPointer != argument) {
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push(d);
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return;
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}
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while (o->name != 0) {
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if (strcmp(o->name, argument) == 0) {
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(*(o->function)) ();
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return;
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}
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o++;
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}
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fprintf(stderr, "math: %s: syntax error.\n", argument);
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exit(-1);
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}
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int math_main(int argc, char **argv)
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{
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if (argc < 1 || *argv[1]=='-')
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usage(math_usage);
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while (argc >= 2) {
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stack_machine(argv[1]);
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argv++;
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argc--;
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}
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stack_machine(0);
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exit( TRUE);
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}
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