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0
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1 /*
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2 Very Simple Calculator (Parser Part, Tree Printer)
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3 $Id$
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4 */
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5
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6 #include <stdio.h>
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19
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7 #include <stdlib.h>
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8 #include "s-token.h"
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9
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10 // extern int label;
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11 // extern char *comments;
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0
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12
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13 int variable[48];
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14
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15 typedef struct node {
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16 struct node *left;
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17 struct node *right;
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18 int type;
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19 int value;
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20 } node;
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21
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22 static node *expr();
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23 static node *aexpr();
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24 static node *mexpr();
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25 static node *term();
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26 static node *new_node();
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27 static void print_node();
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28
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29 static node *
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30 new_node(type,value,left,right)
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31 int type;
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32 int value;
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33 node *left;
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34 node *right;
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35 {
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36 node *d;
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37 d = (node *)malloc(sizeof(node));
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38 d->type = type;
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39 d->value = value;
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40 d->left = left;
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41 d->right = right;
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42 return d;
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43 }
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44
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45 static int tree_level = 0;
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46
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47 static void
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48 print_node(d)
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49 node *d;
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50 {
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51 int i;
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52 for(i=0;i<tree_level;i++) { putchar(' '); }
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53 switch(d->type) {
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54 case '0':
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55 printf("value(%d",d->value);
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56 break;
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57 case 'v':
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58 printf("variable(%c",d->value+'a');
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59 break;
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60 default:
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61 printf("node(%c",d->type);
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62 }
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63 if(d->left) {
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64 tree_level++;
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65 printf(",(\n"); print_node(d->left); printf(")");
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66 tree_level--;
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67 }
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68 if(d->right) {
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69 tree_level++;
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70 printf(",(\n"); print_node(d->right); printf(")");
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71 tree_level--;
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72 }
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73 printf(")");
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74 }
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75
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76 static node *
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77 expr()
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78 {
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79 node *d;
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80
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81 d = aexpr();
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82 while(last_token!=EOF) {
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83 switch(last_token) {
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84 case '>':
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85 d = new_node('>',0,d,aexpr());
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86 break;
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87 case '=':
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88 d = new_node('=',0,d,aexpr());
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89 break;
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90 case ')':
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91 return d;
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92 default:
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93 error("Bad expression");
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94 return d;
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95 }
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96 }
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97 return d;
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98 }
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99
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100 static node *
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101 aexpr()
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102 {
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103 node *d;
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104
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105 d = mexpr();
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106 while(last_token!=EOF) {
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107 switch(last_token) {
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108 case '-':
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109 d = new_node('-',0,d,mexpr());
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110 break;
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111 case '+':
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112 d = new_node('+',0,d,mexpr());
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113 break;
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114 default:
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115 return d;
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116 }
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117 }
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118 return d;
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119 }
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120
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121 static node *
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122 mexpr()
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123 {
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124 node *d;
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125
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126 d = term();
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127 while(last_token!=EOF) {
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128 switch(last_token) {
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129 case '*':
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130 d = new_node('*',0,d,term());
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131 break;
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132 case '/':
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133 d = new_node('/',0,d,term());
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134 break;
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135 default:
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136 return d;
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137 }
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138 }
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139 return d;
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140 }
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141
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142 static node *
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143 term()
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144 {
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145 node *d;
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146
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147 lvalue= -1;
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148 token();
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149 if(last_token==EOF) {
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150 error("Term expected");
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151 }
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152 switch(last_token) {
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153 case '0':
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154 d = new_node('0',value,NULL,NULL);
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155 token();
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156 return d;
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157 case 'v':
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158 d = new_node('v',value,NULL,NULL);
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159 token();
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160 return d;
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161 case '(':
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162 d = expr();
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163 if(last_token != ')') {
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164 error("Unbalanced parenthsis");
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165 }
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166 token();
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167 return d;
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168 default:
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169 token();
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170 error("Unknown term");
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171 return 0;
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172 }
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173 }
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174
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175 int
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176 main()
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177 {
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178 node *d;
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179 char buf[BUFSIZ];
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180
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181 while (fgets(buf,BUFSIZ,stdin)) {
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182 printf("%s\n",buf);
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183 ptr = buf;
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184 d = expr();
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185 tree_level = 0;
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186 print_node(d);
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187 printf(".\n\n");
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188 fflush(stdout);
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189 }
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190 return 0;
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191 }
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192
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193
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194 /* end */
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