1 // lex_analyzer.cpp : 定义控制台应用程序的入口点。  2 //词法分析器  3 /*  4 sys:  5 1-10:关键字  6 10:标识符  7 11:数字  8 //比较区  9 20:< 10 21:<= 11 22:> 12 23:>= 13 24:= 14 25:== 15 //运算区 16 26:* 17 27:/ 18 28:+ 19 29:- 20 //分隔符号区 21 30:; 22 31:( 23 32:) 24 33:{ 25 34:} 26 35:\n 27 -1 28 1000:# 29 */ 30 #include "stdafx.h" 31 #include <iostream> 32 #include <sstream> 33 #include <string> 34 using namespace std; 35 string ss; 36 int scanner(); 37 const string key[] = {"int","main","return","if","for"};//定义关键字 38 stringstream prog; 39 int _tmain(int argc, _TCHAR* argv[]) 40 { 41     char ch = NULL; 42     stringstream s; 43     int row=0;//行号 44     int id_code;//识别码 45     cout << "please input some C/C++ code" << endl; 46     while (ch != ‘#‘) 47     { 48         cin.get(ch); 49         s << ch; 50     } 51     ss = s.str(); 52     do{ 53          id_code= scanner(); 54          switch (id_code) 55          { 56          case -1: cout << "Error in row " << row << "!" << endl; break; 57          case 35: row = row++; break; 58          case 1000:break; 59          default: cout << "(" << id_code << "," << prog.str() << ")" << endl; break; 60              break; 61          } 62     } while (id_code !=1000); 63     return 0; 64 } 65 int scanner() 66 { 67     static int  point=0; 68     prog.str("");//清空 69     char cha = NULL; 70     int syn; 71     //过滤掉空格 72     do 73     { 74         cha = ss[point++]; 75     } while (cha == ‘ ‘); 76     //识别标识符或关键字，标识符以_或字母开头 77     if (cha >= ‘a‘&&cha <= ‘z‘ || cha >= ‘A‘&&cha <= ‘Z‘ || cha == ‘_‘) 78     { 79         while (cha >= ‘a‘&&cha <= ‘z‘ || cha >= ‘A‘&&cha <= ‘Z‘ || cha == ‘_‘ || cha >= ‘0‘&&cha <= ‘9‘) 80         { 81             prog << cha; 82             cha = ss[point++]; 83         } 84         --point; 85         syn = 10; 86             //识别关键字 87         for (int i = 0; i < sizeof(key) / sizeof(key[0]); i++) 88         { 89             if (prog.str() == key[i]) 90                 syn = i; 91         } 92     } 93     //识别数字 94     else if (cha >= ‘0‘&&cha <= ‘9‘) 95     { 96         while (cha >= ‘0‘&&cha <= ‘9‘) 97         { 98             prog << cha; 99             cha = ss[point++];100         }101         --point;102         syn = 11;103     }104     else switch (cha)105     {106     case ‘<‘:107         prog << cha;108         cha = ss[point++];109         if (cha == ‘=‘)110         {111             syn = 21;112             prog << cha;113         }else {114             syn = 20;115             --point;116         }117         break;118     case ‘>‘:119         prog << cha;120         cha = ss[point++];121         if (cha == ‘=‘)122         {123             syn = 23;124             prog << cha;125         }126         else {127             syn = 22;128             --point;129         }130         break;131     case ‘=‘:132         prog << cha;133         cha = ss[point++];134         if (cha == ‘=‘)135         {136             syn = 25;137             prog << cha;138         }139         else {140             syn = 24;141             --point;142         }143         break;144     case‘*‘:syn = 26; prog << cha; break;145     case‘/‘:syn = 27; prog << cha; break;146     case‘+‘:syn = 28; prog << cha; break;147     case‘-‘:syn = 29; prog << cha; break;148     case‘;‘:syn = 30; prog << cha; break;149     case‘(‘:syn = 31; prog << cha; break;150     case‘)‘:syn = 32; prog << cha; break;151     case‘{‘:syn = 33; prog << cha; break;152     case‘}‘:syn = 34; prog << cha; break;153     case‘\n‘:syn = 35; break;154     case ‘#‘:syn = 1000; prog << cha; break;155     default: syn = -1; break;156     }157     return syn;158 }