算符优先分析

算符优先分析.h

#include <iostream>
#include <list> 
using namespace std;

//创建一个list容器的实例LISTCHAR 
typedef list<char> LISTCHAR; 

//优先关系比较数组，其中'<','>'和'='表示优先关系，1，2....6表示6种类型的错误，而7则是规约完成的标志
char Table[7][7]=...{
        ...{'>','<','<','<','<','>','>'},
        ...{'>','>','<','<','<','>','>'},  
    ...{'>','>','<','<','<','>','>'},  
    ...{'>','>','>','1','2','>','>'},
        ...{'<','<','<','<','<','=','3'},
        ...{'>','>','>','4','5','>','>'},
        ...{'<','<','<','<','<','6','7'},
};

//该函数将比较的终结符转换为优先关系比较数组的下标值
int Change(char ch)
...{
    int t;
    switch(ch)
    ...{
    case '+':t=0;break;
    case '*':t=1;break;
    case '^':t=2;break;
    case 'i':t=3;break;
    case '(':t=4;break;
    case ')':t=5;break;
    case '#':t=6;break;
    }
    return t;
}

//该函数对优先关系比较数组Table[7][7]中的6种错误进行处理
int Error(char a,char b)
...{        
    int error=0;
    char x;
    x=Table[Change(a)][Change(b)];
    switch(x)
    ...{    
    case '1':                   
        ...{    
            cout<<"'i'与'i'之间应有运算符"<<endl;
            error++;
            break;
        }
    case '2':                   
        ...{
            cout<<"'i'与'('之间应有运算符"<<endl;
            error++;
            break;
        }
    case '3':                   
        ...{    
            cout<<"'('后应包括内容"<<endl;
            error++;
            break;
        }
    case '4':                   
        ...{    
            cout<<"')'后应是运算符"<<endl;
            error++;
            break;
        }
    case '5':                   
        ...{    
            cout<<"')'与'('间要有运算符"<<endl;
            error++;
            break;
        }
    case '6':                   
        ...{     
            cout<<"error six";
            error++;
            break;
        }
    }
    return error;
}

//该函数获得符号栈list1的栈定终结符
char GetListFinal(list<char> list1)         
...{    
    char ch1;
    list<char>::iterator l1;
    for(l1=list1.begin();l1!=list1.end();++l1)
    ...{    
        if(*l1<'A'|| *l1>'Z')
        ...{    
            ch1=*l1;
            break;    
        }
    }
    return ch1;
}

//该函数为规约和移进的中间过程的打印
void Print(int i,list<char> list1,list<char> list2)
...{    
    list<char>::iterator l1;
    list1.reverse();
    cout<<i<<' ';
    for(l1=list1.begin();l1!=list1.end();++l1)
        cout<<*l1;
    cout<<" ";
    for(l1=list2.begin();l1!=list2.end();++l1)
        cout<<*l1;
    cout<<" ";
}

算符优先分析.cpp

#include "算符优先分析.h"

void main()
...{    
    cout<<"**************************算符优先分析的文法************************"<<endl;
    cout<<"**            E->E+T|T                  **"<<endl;
    cout<<"***            T->T*F|F                 ***"<<endl;
    cout<<"****            F->P^F|P                ****"<<endl;
    cout<<"***            P->(E)|i                 ***"<<endl;
    cout<<"**                ----2008年5月12日          **"<<endl;
    cout<<"********************************************************************"<<endl;
    
    int i=0,j,k,error=0;
    char ch,ch1,ch2;
    
    LISTCHAR  list1;                //list1存放符号栈的内容
    LISTCHAR  list2;                //list2存放输入串的内容
    LISTCHAR::iterator l;           //定义list容器的迭代子
    list1.push_back('#');           //给符号栈中预置'#'
    cout<<"输入要分析的字符串,以#结束:"<<endl;
        cout<<"        ==>:";
    
    do...{                //将输入串存入list1中    
        ch=cin.get();
        list2.push_back(ch); 
        
    }while(ch!='#');
    cout<<endl;
    
    cout<<"步骤"<<' '<<"符号栈"<<" "<<"输入串"<<" "<<"动作"<<endl;
    Print(i,list1,list2);
    cout<<"初始化"<<endl;
    
    do...{        
        ch1=GetListFinal(list1);                    //取得list1的首个终结符        
        ch2=list2.front();                              //取得list2的首个字符
        
        error=Error(ch1,ch2);                           //检查输入串有无错误
        if(error==0)                                    //error=0表示输入串无错误
        ...{    
            j=Change(ch1);                          //将要比较的两个终结符转换为优先关系比较数组Table的下标
            k=Change(ch2);
            
            if(Table[j][k]=='<' || Table[j][k]=='=')   //进行移进操作处理
            ...{    
                list1.push_front(ch2);
                list2.pop_front();
                i++;
                Print(i,list1,list2);
                cout<<"移进"<<endl;    
                
            }
            
            else if(Table[j][k]=='>')            //进行规约操作处理
            ...{    
                switch(ch1)
                ...{
                case 'i':                //规约的终结符为'i'
                    ...{    
                        list1.pop_front();
                        list1.push_front('E');
                        i++;
                        Print(i,list1,list2);
                        cout<<"归约,E->i"<<endl;                        
                        break;
                    }
                case '+':                //规约的终结符为'+'
                    ...{
                        list1.pop_front();
                        list1.pop_front();
                        list1.pop_front();
                        list1.push_front('E');
                        i++;
                        Print(i,list1,list2);
                        cout<<"归约,E->E+T"<<endl;    
                        break;
                    }
                                case '*':                 //规约的终结符为'*'
                    ...{
                        list1.pop_front();
                        list1.pop_front();
                        list1.pop_front();
                        list1.push_front('T');
                        i++;
                        Print(i,list1,list2);
                        cout<<"归约,T->T*F"<<endl;
                        break;
                    }
                case '^':                //规约的终结符为'^'
                    ...{
                        list1.pop_front();
                        list1.pop_front();
                        list1.pop_front();
                        list1.push_front('F');
                        i++;
                        Print(i,list1,list2);
                        cout<<"归约,F->P^F"<<endl;            
                        break;
                    }
                                case ')':                //规约的终结符为')'
                    ...{
                        list1.pop_front();
                        list1.pop_front();
                        list1.pop_front();
                        list1.push_front('P');
                        i++;
                        Print(i,list1,list2);
                        cout<<"归约,P->(E)"<<endl;    
                        break;
                    }
                    
                }    
            }
            
            if(Table[j][k]=='7')                //'#'配对，规约完成
            ...{    
                cout<<"归约完毕!"<<endl;
                break;
            }
        }
        else break;
    }while(1);
    
}