简单的词法分析小程序

实验：词法分析

一.实验目的：编写一个词法分析

    实验要求：输入：源程序字符串

                 输出：二元组（种别，单词本身）

二.词法分析程序设计

   词法规则：字母<a|b|c|...|z>

                 数字<0|1|2|...|9>

                整数常数：<数字>

                标识符：<变量〉

               关键字：<main|scanf|printf|...|const>

               运算符：<+|-|*|...|:=>

               界符   :<(|)|,|;|.>

   各单词对应的种别码

 

                

三：源代码展示

#include<stdio.h>
#include<malloc.h> 
#include<stdlib.h>
#include<ctype.h>
typedef struct node
{
    char ch;
    struct node *next;
}QNode,*QueuePtr;

typedef struct
{
    QueuePtr front;
    QueuePtr rear;
}LinkQueue;

LinkQueue Q;
QueuePtr p;        //定义一个指针变量 
char *keyword[30]={"main","scanf","printf","void","int","float","double","char","long","short","signed",
               "struct","do","while","for","switch","case","break","continue","if","define","typedef","union",
                "static","sizeof","return","extern","goto","auto","const"};
char *operatornum[6]={"+","-","*","/","++","--"};  
char *comparison[8]={"<","<=","=",">",">=","<>","==","!="};  
char *interpunction[8]={",",";",":=",".","(",")","{","}"};  
char *biaoshifu[6]={"%","$","^","&","_","#"};   //特殊标识符  
char *zhushifu[3]={"//","/*","*/"};          //注释符  
char *luoji[3]={"&&","||","!"};             //逻辑运算符  
char *k="";

void InitQueue()      //初始化一个带节点的空队列 
{
    Q.front=Q.rear=(QueuePtr)malloc(sizeof(QNode));
    if(!Q.front)   
      exit(0);
    Q.front->next=NULL;
}
void Printf()
{
    QueuePtr p;        //定义一个指针变量 
    p=Q.front;
    while(!(p==Q.rear))
    {
        p=p->next;
        printf("%c",p->ch);
    }
    printf("
");
}
void Creat()    //创建队列 
{
    char ch;
    QueuePtr p;
    printf("请输入您要分析的字符串");
    ch=getchar();
    while(ch!='@')
    {
        p=(QueuePtr)malloc(sizeof(QNode));
        p->ch=ch;
        p->next=NULL;
        Q.rear->next=p;
        Q.rear=p;
        ch=getchar();
    }
}


int search(char searchstr[],int wordtype)//符号匹配   
{  
    int i;  
    switch (wordtype)  
    {  
        case 1:  
            for(i=0;i<30;i++)  
            {  
                if(strcmp(keyword[i],searchstr)==0)  
                return i;  
            }  
            break;  
        case 2:  
            for(i=0;i<=5;i++)  
            {  
                if(strcmp(operatornum[i],searchstr)==0)  
                return 30+i;  
            }  
         break;  
              
        case 3:   
            for(i=0;i<=7;i++)  
            {  
             if(strcmp(comparison[i],searchstr)==0)  
                return 36+i;  
            }  
            break;  
     
        case 4:   
            for(i=0;i<=7;i++)  
            {  
                if(strcmp(interpunction[i],searchstr)==0)  
                return 44+i;  
            }  
    
            break;  
        case 5:   
            for(i=0;i<=5;i++)  
            {  
                if(strcmp(biaoshifu[i],searchstr)==0)  
                    return 52+i;  
            }  
            break;  
        case 6:  
             for(i=0;i<=2;i++)  
             {  
                if(strcmp(zhushifu[i],searchstr)==0)  
                    return 58+i;  
            }  
            break;  
        case 7:   
            for(i=0;i<=2;i++)  
            {  
                if(strcmp(luoji[i],searchstr)==0)  
                    return 61+i;  
            }  
        break;  
    }  
  
    return -1;  
}  
void Analyze()
{
    char str;
    char letter[20];  
    char num[20];  
    char other[20];  
    int i;
    do      
    {
        Q.front=Q.front->next;        //获取单个字符 
        str=Q.front->ch;
        if (isalpha(str)!=0)        //如果是字符 
        {
            i=-1;
           while (isalnum(str)!=0)  
          {  
            letter[++i]=str;  
            Q.front=Q.front->next;
            str=Q.front->ch;  
          }  
           letter[i+1]='';  
           if (search(letter,1)!=-1)  
          {  
            printf("( %d,%s )
",search(letter,1),letter);  
            
          }  
          else  
          {  
              printf("( %d,%s )
",64,letter);   
           }  
        }    
        else  
        {  
            if (isdigit(str)!=0)  
            {
                i=-1;
                while (isdigit(str)!=0)  
                {  
                   num[++i]=str;  
                   Q.front=Q.front->next;
                   str=Q.front->ch; 
                }  
                if(isalpha(str)!=0)         //数字后面是字符   
                {  
                    while(isspace(str)==0)  
                   {  
                     num[++i]=str; 
                     Q.front=Q.front->next; 
                     str=Q.front->ch; 
                    }  
                   num[i+1]='';  
                   printf("错误！非法标识符：%s
",num);  
                
                }  
                num[i+1]='';  
                printf("( %d,%s )
",65,num);  
            }
            else  
            {
              i=-1;    
              if (isspace(str)!=0)  
              {  
                 Q.front=Q.front->next;
                 str=Q.front->ch;
                 
              }  
              while ((isspace(str)==0)&&(isalnum(str)==0))  
              {  
                  Q.front=Q.front->next;
                 str=Q.front->ch; 
                 other[++i]=str;  
                
                 
               }  
                  other[i+1]='';  
              if (search(other,2)!=-1)  
                  printf("( %d,%s )
",search(other,2),other);  
              else if (search(other,3)!=-1)  
                  printf("( %d,%s )
",search(other,3),other);  
              else if (search(other,4)!=-1)  
                  printf("( %d,%s )
",search(other,4),other);  
              else if (search(other,5)!=-1)  
                  printf("( %d,%s )
",search(other,5),other);  
              else if (search(other,6)!=-1)  
                  printf("（ %s,注释符号 ）
",other);  
              else if (search(other,7)!=-1)  
                  printf("( %d,%s )
",search(other,7),other);  
              else   
                  printf("错误！非法字符：%s
",other);  
            }
        }  
    }while(Q.front!=Q.rear);  
     printf("词法分析结束，谢谢使用！
"); 
}

int main()
{
    
    InitQueue();    //创建空链队列 
    Creat();        //创建队列 
    Printf();       //输出队列 
    Analyze();      //词法分析 
    return 0;
}