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1 /*
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2 Very Simple Calculator
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3 $Id$
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4 */
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5
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6 #include "s-compile.h"
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7
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8 int variable[48];
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9
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10 static int expr();
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11 static int aexpr();
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12 static int mexpr();
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13 static int term();
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14
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15
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16 static int
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17 expr()
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18 {
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19 int d,assign;
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20
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21 d = aexpr();
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22 assign = lvalue;
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23 while(last_token!=EOF) {
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24 switch(last_token) {
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25 case '>':
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26 d = (d > aexpr());
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27 break;
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28 case '=':
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29 if(assign>=0) {
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30 d = expr();
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31 variable[assign] = d;
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32 break;
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33 } else {
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34 error("Bad assignment");
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35 break;
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36 }
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37 case ')':
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38 return d;
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39 default:
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40 error("Bad expression");
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41 return d;
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42 }
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43 }
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44 return d;
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45 }
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46
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47 static int
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48 aexpr()
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49 {
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50 int d;
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51
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52 d = mexpr();
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53 while(last_token!=EOF) {
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54 switch(last_token) {
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55 case '-':
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56 d -= mexpr();
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57 break;
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58 case '+':
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59 d += mexpr();
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60 break;
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61 default:
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62 return d;
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63 }
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64 }
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65 return d;
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66 }
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67
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68 static int
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69 mexpr()
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70 {
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71 int d;
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72
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73 d = term();
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74 while(last_token!=EOF) {
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75 switch(last_token) {
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76 case '*':
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77 d *= term();
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78 break;
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79 case '/':
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80 d /= term();
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81 break;
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82 default:
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83 return d;
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84 }
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85 }
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86 return d;
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87 }
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88
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89 static int
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90 term()
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91 {
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92 int d;
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93
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94 lvalue= -1;
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95 token();
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96 if(last_token==EOF) {
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97 error("Term expected");
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98 }
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99 switch(last_token) {
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100 case '0':
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101 d = value;
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102 token();
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103 return d;
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104 case 'v':
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105 d = lvalue = value;
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106 token();
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107 return variable[d];
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108 case '(':
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109 d = expr();
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110 if(last_token != ')') {
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111 error("Unbalanced parenthsis");
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112 }
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113 token();
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114 return d;
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115 default:
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116 token();
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117 error("Unknown term");
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118 return 0;
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119 }
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120 }
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121
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122 int
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123 main()
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124 {
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125 int d;
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126 char buf[BUFSIZ];
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127
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128 while (fgets(buf,BUFSIZ,stdin)) {
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129 ptr = buf;
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130 d = expr();
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131 printf("%s = 0x%08x = %d\n",buf,d,d);
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132 fflush(stdout);
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133 }
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134 return 0;
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135 }
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136
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137 /* end */
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