编译原理实验，词法分析器及判错

叁歲伎倆 2023-02-17 02:30 13阅读 0赞

配套课本忘了盒盒盒

在这里插入代码片
    #include <stdio.h>
    #include <string.h>
    char str1[80],token[20];
    //声明保留字符串 方便比对
    char *rwtab[6] = {
        "begin","if","then","while","do","end"};
    //syn为token对应的码 tar为switch对应的输出类型keyword
    int syn,tar ;
    //num为token索引
    int num = 0;
    //k为str1索引
    int k=0;
    //ch为k当前对应的str1的字符
    char ch ;
    
    int kk = 0;
    
    void Irparser();
    void yucu();
    void statement();
    void expression();
    void term();
    void factor();
    void scanner();
    
    int main()
    {
        
        int count=0;
        printf("\nplease input string\n") ;
        do{
        
            scanf("%c",&str1[count++]);
        }while(str1[count-1]!='#');
    
    	scanner();
        Irparser();
        return 0;
    }
    
    void scanner(){
        
        for (int j = 0; j < 8; ++j)
            token[j]= NULL;
        
        while (1){
        
            if(str1[k++] != ' '){
        
                ch = str1[k-1];
                break;
            }
        };
    
        token[0] = ch;
        if(ch>='0'&&ch<='9'){
        
            num = 0 ;
            while(ch>='0'&&ch<='9'){
        
                token[num++] = ch;
                ch = str1[k++];
            }
            k--;
            syn = 11;
        } else if ((ch>='A'&&ch<='Z')||(ch>='a'&&ch<='z')){
        
            num = 0;
            while((ch>='A'&&ch<='Z')||(ch>='a'&&ch<='z')||(ch>='0'&&ch<='9')){
        
                token[num++] = ch;
                ch = str1[k++];
            }
    
            token[num++] = '\0';
            k--;
            syn = 10;
    
            for (int i = 0; i < 6; ++i) {
        
                if(strcmp(token,rwtab[i])==0){
        
                    syn = i+1;
                    break;
                }
            }
    
        } else {
        
            switch(ch){
        
                case '<':
                    ch = str1[k++];
                    if(ch == '>'){
        
                        syn = 21;
                        token[1] = ch;
                    }else if(ch == '='){
        
                        syn =  22;
                        token[1] = ch;
                    }else{
        
                        syn = 20;
                        k--;
                    }
                    break;
                case '>':
                    ch = str1[k++];
                    if(ch == '='){
        
                        syn = 24;
                        token[1] = ch;
                    } else{
        
                        syn = 23;
                        k--;
                    }
                    break;
                case ':':
                    ch = str1 [k++];
                    if(ch == '='){
        
                        syn = 18;
                        token[1] = ch;
                    } else{
        
                        syn = 17;
                        k--;
                    }
                    break;
                case '+':
                    ch = str1 [k];
                    syn = 13;
                    
                    break;
                case '-':
                    ch = str1 [k];
                    syn = 14;
                    
                    break;
                case '*':
                    ch = str1 [k];
                    syn = 15;
                    
                    break;
                case '/':
                    ch = str1 [k];
                    syn = 16;
                    
                    break;
                case '=':
                    ch = str1 [k];
                    syn = 25;
                    
                    break;
                case ';':
                    ch = str1 [k];
                    syn = 26;
                    
                    break;
                case '(':
                    ch = str1 [k];
                    syn = 27;
                    
                    break;
                case ')':
                    ch = str1 [k];
                    syn = 28;
                    
                    break;
                case '#':
                    ch = str1 [k];
                    syn = 0;
                    
                    break;
                default:
                    syn = -1;
            }
        }
    }
    
    void Irparser(){
        
    	//递归下降分析 
    	if(syn == 1)
    	{
        
    		scanner();
    		yucu();
    		if(syn == 6)
    		{
        
    			scanner();
    			if(syn == 0 && kk == 0)
    			{
        
    				printf("success!");
    			}	
    		}
    		else
    		{
        
    			if(kk!= 1)
    			printf("error,lost 'end'");
    			kk = 1;
    		}
    	}
    	else
    	{
        
    		printf("error,lost 'begin'");
    		kk = 1;
    	}
    	
    }
    
    void yucu(){
        
    	//语句串分析 
    	statement();
    	while(syn == 26)
    	{
        
    		scanner();
    		statement();
    	}
    }
    
    void statement(){
        
    	//标识符
    	if(syn == 10)
    	{
        
    		scanner();
    		if(syn == 18)
    		{
        
    			scanner();
    			expression();
    		}
    		else
    		{
        
    			printf("error,':='");
    			kk = 1;
    		}
    	 }
    	 else
    	 {
        
    	 	printf("error,语句错误");
    	 	kk = 1;
    	 }
    }
    
    void expression(){
        
    	//分析函数 
    	term();
    	while(syn == 13 || syn == 14)
    	{
        
    		scanner();
    		term();
    	}
    }
    
    void term(){
        
    	//函数分析子函数
    	factor();
    	while(syn == 15 || syn == 16)
    	{
        
    		scanner();
    		factor();
    	 } 
    }
    
    void factor(){
        
    	if(syn == 10 || syn ==11)
    		scanner();
    	else if (syn == 27)
    	{
        
    		scanner();
    		expression();
    		if (syn == 28)
    		scanner();
    		else
    		{
        
    			printf("'）'error");
    			kk = 1;
    		}
    	}
    	else{
        
    		printf("error,表达式错误");
    		kk = 1; 
    	}
    }