词法分析.cpp

武汉理工大学编译原理课程实验源代码之词法分析器

#include <iostream>
#include <vector>
#include <utility>
#include <string>
#include <fstream>
#include <algorithm>
#include <cstdlib>
using namespace std; 

string file_name; 
 
string GetText(); 

string GetWord(string str,int i,int& j);

int DeleteNull(string str,int i);

bool IsBoundary(string str,int i);

bool IsOperation(string str,int i);

void OutFile(vector<pair<int,string> > v);

vector<pair<int,string> > analyst(vector<string> vec);

bool IsKey(string str);

int main()
{
    string com1=" ";
    string com2="\n";
    string fileline=GetText();
    int begin=0,end=0;
    vector<string> array;
    do
    {
        begin=DeleteNull(fileline,begin);
        string nowString;
        nowString=GetWord(fileline,begin,end);
        if(end==-1)
			break;
        if(nowString.compare(com1)&&nowString.compare(com2))
            array.push_back(nowString);
        begin=end+1; 
    }while(true);
    vector<pair<int,string> > mid_result;
    mid_result=analyst(array);
    OutFile(mid_result);
    cout<<"\n";
    cout<<"已完成词法分析";
    cout<<"\n";
    system("pause");
 return 0;
} 

string GetText()
{   
    string file_name1;
 cout<<"源文件名：";
 cin>>file_name1;
 ifstream infile(file_name1.c_str(),ios::in);
    cout<<endl;
    char f[1000];
 infile.getline(f,1000,EOF);
 infile.close();
 return f;
} 


string GetWord(string str,int i,int & j)
{
       string no_use("{}() , ;  \n+=*/-<>\"");
       j=str.find_first_of(no_use,i);
       if(j==-1)
           return "";
       if(i!=j)
           j--; 
       return str.substr(i,j-i+1);
} 


int DeleteNull(string str,int i)
{
    for(;;i++)
        if(str[i]!=' '&&str[i]!='\n')
            return i;
} 


bool IsBoundary(string str,int i)
{
     int t;
     char arr[6]={',',';','{','}','(',')'};
     for (t=0;t<6;t++) 
         if(str[i]==arr[t])
             return true;
     return false;
} 


bool IsOperation(string str,int i)
{
     int t;
     char arr[7]={'+','-','*','/','=','<','>'};
     for (t=0;t<7;t++) 
         if(str[i]==arr[t])
             return true;
     return false;
} 


void OutFile(vector<pair<int,string> > v)
{
    cout<<"目标文件名：";
 cin>>file_name;
    ofstream outfile(file_name.c_str(),ios::out);
    cout<<endl;
    int i;

    for(i=0;i<v.size();i++)
        outfile<<"<"<<v[i].first<<" , \""<<v[i].second<<"\">"<<endl;

    outfile.close();
    return;
} 


vector<pair<int,string> > analyst(vector<string> vec)
{
     vector<pair<int,string> > temp;
     int i;
     for(i=0;i<vec.size();i++)
     {
         if(vec[i].size()==1)
         {
             if((vec[i]==">"||vec[i]=="<"||vec[i]=="!")&&vec[i+1]=="=")
             {
                   string jk=vec[i];
                   jk.append(vec[++i],0,1);
                   pair<int,string> pp(4,jk);
                   temp.push_back(pp);
                   continue;
             }
             if((vec[i]=="+"&&vec[i+1]=="+")||(vec[i]=="-"&&vec[i+1]=="-"))
             {
                   string jk=vec[i];
                   jk.append(vec[++i],0,1);
                   pair<int,string> pp(4,jk);
                   temp.push_back(pp);
                   continue;
             }
             if(IsBoundary(vec[i],0))
             {
                   pair<int,string> pp(5,vec[i]);
                   temp.push_back(pp);
             }
             else if(IsOperation(vec[i],0))
             {
                   pair<int,string> pp(4,vec[i]);
                   temp.push_back(pp);
             }
             else if(vec[i][0]<='9'&&vec[i][0]>='0')
             {
                   pair<int,string> pp(3,vec[i]);
                   temp.push_back(pp);
             }
             else
             {
                   pair<int,string> pp(2,vec[i]);
                   temp.push_back(pp);
             }
         }
         else if(vec[i][0]<='9'&&vec[i][0]>='0')
         {
              pair<int,string> pp(3,vec[i]);
              temp.push_back(pp);
         }
         else if(IsKey(vec[i]))
         {
              pair<int,string> pp(1,vec[i]);
              temp.push_back(pp);
         }
         else
         {
              pair<int,string> pp(2,vec[i]);
              temp.push_back(pp);
         }
     }
     return temp;   
} 


bool IsKey(string str)
{
     string p[16]={"char","double","int","long","double","float","for","while","do","break","continue","switch","short","case","return","if"};
     vector<string> ppp(p,p+16);
     int u;
     for(u=0;u<ppp.size();u++)
         if(!str.compare(ppp[u]))
             return true;
     return false;
}