syntax.h

计算机科学与技术专业课程编译原理的课程实验代码

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int Errors = 0, Level = -1;
int type, Line=0;//种别,行号
int Begin = 0;
char p[20];



ifstream fin("words.txt");
ofstream fout("errors.txt");

void Input();//从词法分析的结果中读入字符
void ErrorOut(int line, char *p, int code);//出错处理函数
int ConstAna(int ProStep);//常量说明部分,保留字CONST  
int Var(int ProStep);//Var变量定义
int Expression(int);//处理表达式
int Factor();//因子处理函数
int Item();//项
int Condition();//条件处理函数
int Sentence() ;//句子处理函数
void Syntax() ; //程序块

void Input()
{
    fin >> Line >> type >> p;
    return;
}

struct Identity
{
    char id[20];
    int type;//0 - const, 1 - var, 2 - Procedure
    int level;
    int value;
    Identity *next;
} *Head, *End;

void ErrorOut(int line, char *p, int code)
{
    Errors++;
    char ErrorCode[80];
    switch (code)
    {
        case 0 :strcpy(ErrorCode,"  ");break;
        case 1 :strcpy(ErrorCode," 常数说明中的\"=\"写成\":=\"。 ");break;
        case 2 :strcpy(ErrorCode," 常数说明中的\"=\"后应是数字 ");break;
        case 3 :strcpy(ErrorCode," 常数说明中的标示符后应是\"=\" ");break;
        case 4 :strcpy(ErrorCode," const, var, procedure 后应为标示符。 ");break;
        case 5 :strcpy(ErrorCode," 漏掉了','或';' ");break;
        case 7 :strcpy(ErrorCode," 应是语句开始符。 ");break;
        case 9 :strcpy(ErrorCode," 程序结尾丢了句号'.' ");break; 
        case 11:strcpy(ErrorCode," 不可识别的标示符。");break;
        case 12:strcpy(ErrorCode," 赋值语句中，赋值号左部标示符属性应是变量 ");break;
        case 13:strcpy(ErrorCode," 赋值语句左部标识符后应是赋值号\":=\" ");break;
        case 14:strcpy(ErrorCode," call后应为标识符 ");break;
        case 15:strcpy(ErrorCode," call后标识符属性应为过程 ");break;
        case 16:strcpy(ErrorCode," 条件语句中丢了\"then\" ");break;
        case 17:strcpy(ErrorCode," 丢了'END'或';' ");break;
        case 18:strcpy(ErrorCode," while型循环语句中丢了\"do\" ");break;
        case 19:strcpy(ErrorCode," 语句后的符号不正确 ");break;
        case 20:strcpy(ErrorCode," 应为关系运算符 ");break;
        case 21:strcpy(ErrorCode," 表达式内标识符属性能是过程 ");break;
        case 22:strcpy(ErrorCode," 表达式中漏掉右括号 ");break;
        case 23:strcpy(ErrorCode," 因子后的非法符号 ");break;
        case 24:strcpy(ErrorCode," 表达式的开始符不能是此符号 ");break;
        case 31:strcpy(ErrorCode," 数越界 ");break;
        case 32:strcpy(ErrorCode," read语句括号中的标识符不是变量 ");break;
        case 33:strcpy(ErrorCode," 重复定义 ");break;
        case 34:strcpy(ErrorCode," BEGIN与END不匹配 ");break;
        case 35:strcpy(ErrorCode," 常数说明部分已结束。 ");break;
        case 36:strcpy(ErrorCode," 变量说明部分已结束。 ");break;
    }
    if(!code)
    {
        Errors--;
        return;
    }    
    cout << "Line (" << line << ") : " << p << ErrorCode << endl;
    fout << "Line (" << line << ") : " << p << ErrorCode << endl;
}

int ConstAna(int ProStep)//常量说明部分,保留字CONST  
{
    int step = 0;
    int flag = 0;
    while(true)
    {
        Input();
        step = (step + 1) % 5;
        if(!step)
        {
            step++;
            flag = 0;
        }    
        if(step == 1)
        {
            if(type != 3) ErrorOut(Line, p, 4);//const, var, procedure 后应为标示符
            else if(ProStep == 0)
            {
                Identity *pId = new Identity;
                strcpy(pId->id,p);
                pId->type = 0;
                pId->next = NULL;
                pId->level = Level;
                if(Head == NULL)
                {
                    End = pId;
                    Head = pId;
                }    
                else
                {
                    End = Head;
                    if(strcmp(End->id,p) == 0)
                    {
                        ErrorOut(Line, p, 33);//重复定义
                        flag = 1;
                    }
                    while(End->next)
                    {
                        End = End->next;
                        if(strcmp(End->id,p) == 0)
                        {
                            ErrorOut(Line, p, 33);//重复定义
                            flag = 1;
                            break;
                        }
                    }
                    if(strcmp(End->id,pId->id) != 0) End->next = pId;
                }
            }
        }    
        if(step == 2)
        {
            if(type == 5)
				ErrorOut(Line, p, 1);//常数说明中的\"=\"写成\":=\"。
            else 
				if(type != 4) 
					ErrorOut(Line, p,3);// 常数说明中的标示符后应是\"=\" 
            else 
				if(strcmp(p,"=") != 0)            
				{                
					ErrorOut(Line, p, 3);  // 常数说明中的标示符后应是\"=\"               
					step--;            
				}        
		}
        if(step == 3)
        {
            if(type != 2) 
				ErrorOut(Line, p, 2);//常数说明中的\"=\"后应是数字
            else
            {
                int num = 0, i = 0;
                while(p[i])
                {
                    num = 10 * num + p[i] - '0';
                    i++;
                }

                if(!flag) 
					End->value = num;
            }    
        }    
        if(step == 4) if(p[0] != ',' && p[0] != ';') 
			ErrorOut(Line, p, 5);//漏掉了','或';'
        if(strcmp(p,";") == 0) return 0;
    }
} 

int Var(int ProStep)//Var变量定义
{
    int step = 0;
    while(true)
    {
        Input();
        step = (step + 1) % 3;
        if(!step) step++;    
        if(step == 1)
        {
            if(type != 3) 
				ErrorOut(Line, p, 4);//const, var, procedure 后应为标示符。
            else if(ProStep == 1)
            {
                Identity *pId = new Identity;
                strcpy(pId->id,p);
                pId->type = 1;
                pId->next = NULL;
                pId->level = Level;
                if(Head == NULL) Head = pId;
                else
                {
                    End = Head;
                    if(strcmp(End->id,p) == 0) ErrorOut(Line, p, 33);
                    while(End->next)
                    {
                        End = End->next;
                        if(strcmp(End->id,p) == 0)//重复定义
                        {
                            ErrorOut(Line, p, 33);
                            break;    
                        }
                    }
                    if(strcmp(End->id,pId->id) != 0) End->next = pId;
                }
            }    
        }
        if(step == 2) 
			if(p[0] != ',' && p[0] != ';') 			
				ErrorOut(Line, p, 5);//漏掉了','或';
        if(strcmp(p,";") == 0) return 0;
    }    
}



int Factor()
{
    if(type == 2) return 0;
    if(type == 3)
    {
        End = Head;
        while(End)
        {
            if(strcmp(p,End->id) == 0) return 0;
            End = End->next;
        }
        return 11;
    }
    if(p[0] == '(')
    {
        Input();
        Expression(0);
    }
    else return 0;
    Input();
    if(p[0] != ')') return 22;
    return 0;
}    

int Item()
{
    int a = Factor();
    ErrorOut(Line, p, a);
    if(p[0] == '*' || p[0] == '/') 
		Input();
    else return 0;
    a = Factor();
    ErrorOut(Line, p, a);
    return 0;
}    

int Expression(int notFirst)//表达式
{
    if(p[0] == '+' || p[0] == '-') Input();
    else if(notFirst) return 0;
    Item();
    Input();
    if(p[0] == '>' || p[0] == '<' || p[0] == '=' || p[0] == '#') return 0;
    Expression(1);
    return 0;
}    

int Condition()  //条件
{
    Input();
    if(strcmp(p,"ODD") == 0) Input();
    Expression(1);
    if(p[0] == '>' || p[0] == '<' || p[0] == '=' || p[0] == '#') Input();
    else return 20;
    Expression(1);
    return 0;
}

int Sentence()   
{
    if(!p) return 0;
    if(strcmp(p,"BEGIN") == 0)
    {
        Begin++;
        Input();
        while(p && strcmp(p,"END") != 0)
        {
            Sentence();
            if(p[0] != ';') Input();
            if(p[0] == ';') Input();
            else ErrorOut(Line, p, 5);//漏掉了','或';'
        }
        Begin--;
        return Begin;
    }
    if(type == 3)
    {
        End = Head;
        while(End)
        {
            if(strcmp(End->id,p) == 0)
            {
                if(End->type != 1) ErrorOut(Line, p, 12);//赋值语句中，赋值号左部标示符属性应是变量
                break;
            }
            End = End->next;
        }
        if(!End || strcmp(End->id,p) != 0) 
			ErrorOut(Line, p, 11);
        Input();
        if(type != 5) 
			ErrorOut(Line, p, 13);
        Input();
        int a = Expression(0);
        if(a) 
			ErrorOut(Line, p, a);
        return 0;
    }
    if(strcmp(p,"CALL") == 0)
    {
        Input();
        if(type != 3)
			ErrorOut(Line, p, 14);
        return 0;
    }
    if(strcmp(p,"IF") == 0)
    {
        int a = Condition();
        ErrorOut(Line, p, a);
        Input();
        if(strcmp(p,"THEN") != 0) 
			ErrorOut(Line, p, 16);
        else Input();
        a = Sentence();
        ErrorOut(Line, p, a);
        return 0;
    }
    if(strcmp(p,"WRITE") == 0)
    {
        Input();
        if(p[0] =='(') 
			Input();
        else 
			ErrorOut(Line, p, 7);
        while(true)
        {
            Expression(0);
            if(p[0] != ',') break;
            else Input();
        }
        if(p[0] != ')') 
			ErrorOut(Line ,p, 22);
        return 0;
    }
    if(strcmp(p,"READ") == 0)
    {
        Input();

        if(p[0] != '(') 
			ErrorOut(Line, p, 7);
        else 
			Input();

        while(type == 3)
        {
            Input();
            if(p[0] != ',') break;
            else 
				Input();
        }
        if(p[0] != ')' ) 
			ErrorOut(Line, p, 22);
        return 0;
    }
    if(strcmp(p,"WHILE") == 0)
    {
        Input();
        int a = Condition();
        ErrorOut(Line, p, a);
        if(strcmp(p,"DO") != 0) Input();

        if(strcmp(p,"DO") != 0) ErrorOut(Line, p, 18);

        else Input();
        a = Sentence();

        ErrorOut(Line, p, a);

        return 0;
    }
    return 0;
}

void Syntax()  //程序块
{

	cout<<"语法分析如下..."<<endl;
    int Step = 0;
    Level ++;
    while(fin >> type >> Line >> p)
    {
        if(type == 0)
        {
            ErrorOut(Line, p, 11);
            continue;
        }
        if(type == 1)
        {
            if(strcmp(p,"CONST") == 0)
            {
                if(Step >= 1) ErrorOut(Line, p, 35);
                ConstAna(Step);
                if(Step < 1) Step = 1;
            }
            if(strcmp(p,"VAR") == 0)
            {
                if(Step >= 2) ErrorOut(Line, p, 36);
                Var(Step);
                if(Step < 2) Step = 2;
            }
            if(strcmp(p,"PROCEDURE") == 0)
            {
                Step = 3;
                Identity *pId = new Identity;
                Input();
                strcpy(pId->id,p);
                pId->level = 0;
                pId->type = 2;
                pId->next =NULL;
                End = Head;
                while(End->next)
                {
                    if(strcmp(pId->id,End->id) == 0)
                    {
                        ErrorOut(Line, p, 33);
                        break;
                    }    
                    End = End->next;
                }
                if(strcmp(pId->id,End->id) != 0) End->next = pId;
                Syntax();    
            }
            if(strcmp(p,"BEGIN") == 0) Step = 4;
        }//End Type = 1
        if(type == 2) ErrorOut(Line, p, 7);
        if(Step == 4)
        {
            int a = Sentence();
            if(a) ErrorOut(Line, p, 34);
            //break;
        }
    }//End While
}