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comparison c/regexParser/main.cc @ 55:883e3473a9f5

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fix
author Masataka Kohagura <kohagura@cr.ie.u-ryukyu.ac.jp>
date Mon, 08 Jun 2015 23:40:09 +0900
parents f540de861cd6
children 8901bc071d33
comparison
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54:f540de861cd6 55:883e3473a9f5
1 /*
2 Very Simple Calculator
3 $Id$
4 */
5
1 #include <stdio.h> 6 #include <stdio.h>
2 #include <stdlib.h>
3 #include <string.h>
4 7
5 typedef struct node { 8 static char *ptr,*last_ptr;
6 struct node *left; 9 static int value,lvalue;
7 struct node *right; 10 static int last_token;
8 int type; 11 static int variable[48];
9 int value; 12
10 } Node, *NodePtr; 13 static int expr();
14 static int aexpr();
15 static int mexpr();
16 static int term();
17 static int token();
18 static void error(char *);
11 19
12 20
13 NodePtr newNode(int type, int value, NodePtr left, NodePtr right) { 21 static int
14 NodePtr d = (NodePtr)malloc(sizeof(Node)); 22 token()
15 d->type = type; 23 {
16 d->value = value; 24 int c,d;
17 d->left = left; 25
18 d->right = right; 26 last_ptr = ptr; /* for error position */
19 return d; 27 c= *ptr;
28 if(!c) {
29 last_token = EOF;
30 return last_token;
31 }
32 ptr++;
33 if (c<=' ') { /* comment */
34 while(*ptr++);
35 ptr--;
36 last_token = EOF;
37 last_ptr = ptr;
38 return last_token;
39 }
40
41 if('0'<=c && c<='9') { /* Decimal */
42 d = c-'0';
43 while((c= *ptr++)) {
44 if('0'<=c && c<='9') {
45 d = d*10 + (c - '0');
46 } else {
47 break;
48 }
49 }
50 c && ptr--;
51 value = d;
52 last_token = '0';
53 return last_token;
54
55 } else if ('a'<=c && c<='z') { /* variable */
56 value = c-'a'; /* return variable reference */
57 last_token = 'v';
58 return last_token;
59 } else {
60 last_token = c;
61 return last_token;
62 return c;
63 }
20 } 64 }
21 65
22 int main(int argc, char **argv) { 66 static int
67 expr()
68 {
69 int d,assign;
23 70
24 for (int i = 1; i < argc ; i++) { 71 d = aexpr();
72 assign = lvalue;
73 switch(last_token) {
74 case '>':
75 d = (d > aexpr());
76 return d;
77 case '=':
78 if(assign>=0) {
79 d = expr();
80 variable[assign] = d;
81 return d;
82 } else {
83 error("Bad assignment");
84 return 0;
85 }
86 case ')':
87 return d;
88 case EOF:
89 return d;
90 default:
91 error("Bad expression");
92 return d;
93 }
94 }
25 95
96 static int
97 aexpr()
98 {
99 int d;
100
101 d = mexpr();
102 switch(last_token) {
103 case '-':
104 d -= aexpr();
105 return d;
106 case '+':
107 d += aexpr();
108 return d;
109 default:
110 return d;
26 } 111 }
112 }
27 113
114 static int
115 mexpr()
116 {
117 int d;
118 d = term();
119 switch(last_token) {
120 case '*':
121 d *= mexpr();
122 return d;
123 case '/':
124 d /= mexpr();
125 return d;
126 default:
127 return d;
128 }
129 }
130
131 static int
132 term()
133 {
134 int d;
135
136 lvalue= -1;
137 token();
138 if(last_token==EOF) {
139 error("Term expected");
140 }
141 switch(last_token) {
142 case '0':
143 d = value;
144 token();
145 return d;
146 case 'v':
147 d = lvalue = value;
148 token();
149 return variable[d];
150 case '(':
151 d = expr();
152 if(last_token != ')') {
153 error("Unbalanced parenthsis");
154 }
155 token();
156 return d;
157 default:
158 token();
159 error("Unknown term");
160 return 0;
161 }
162 }
163
164 static int lineno = 0;
165
166 void
167 error(char *msg)
168 {
169 fprintf(stderr,"%s on line %d\n",msg, lineno);
170 }
171
172 int
173 main()
174 {
175 int d;
176 char buf[BUFSIZ];
177
178 while (fgets(buf,BUFSIZ,stdin)) {
179 ptr = buf;
180 d = expr();
181 printf("%s = 0x%08x = %d\n",buf,d,d);
182 fflush(stdout);
183 lineno++;
184 }
28 return 0; 185 return 0;
29 } 186 }