1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
/* 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"
#ifndef BB_FEATURE_TRIVIAL_HELP
"\nThis 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"
#endif
;
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);
}
|
