0916 编译原理第二次上机实验

#include<stdio.h>
#include<string.h>
void Fenxi(char c,char b);
void word(char a[]);
void number(char a[]);
int i;  //定义全局变量i
int s=1; //用来记录是否存在非法字符
main(){
    char a[50];
    printf("请输入源程序:");
    gets(a);
    printf("您要分析的源程序为:");
    printf("%s",a);
    printf("\n");
    for(i=0;(a[i]!=‘\0‘)&&(i<50)&&s==1;i++)
    {
        if((a[i]>=‘a‘ && a[i]<=‘z‘)||(a[i]>=‘A‘ && a[i]<=‘Z‘))
            word(a);
        else if(a[i]>=‘0‘ && a[i]<=‘9‘)
number(a);
else
            Fenxi(a[i],a[i+1]);
    }
    printf("\n");
}

void number(char a[])  //对数字字符进行扫描分析
{
    char b[50];
    int m,k=0,t;
    m=i;
    while(a[m]>=‘0‘ && a[m]<=‘9‘) 
    {
        b[k]=a[m];   //用数组b存放数组a中的数字
        k++;
        m++;
    }
    i=m-1;
    printf("(11,");
    for(t=0;t<k;t++)
            printf("%c",b[t]);
    printf(")");
}

void word(char a[])   //对字母字符进行扫描分析，并识别保留字
{
    int k=0,m,flag=0,t;
    char b[50];
    char *key[6]={"begin","if","then","while","do","end"};
    m=i;
    while((a[m]>=‘a‘&&a[m]<=‘z‘)||(a[m]>=‘A‘&&a[m]<=‘Z‘))  //用数组b存放数组a中的字母
    {
        b[k]=a[m];  
        k++;
        b[k]=‘\0‘;
        m++;                                                                                                                    
    }
    i=m-1;
    for(t=0;t<6;t++)
    {
        if(strcmp(b,key[t])==0)  //将数组b与关键字进行比较
        {
            printf("(%d,%s)",t+1,key[t]);  //输出关键字
            flag=1;
        }
    }
    if(flag==0)
    {
        printf("(10,%s)",b);   //输出标识符
    }
}
void Fenxi(char c,char b)  //对特殊字符进行扫描分析
{
    switch(c){
        case ‘ ‘:
            break;
        case ‘+‘:
            printf("(13,+)");
            break;
        case ‘-‘:
            printf("(14,-)");
            break;
        case ‘*‘:
            printf("(15,*)");
            break;
        case ‘/‘:
            printf("(16,/)");
            break;
        case ‘:‘:
            if(b==‘=‘)
            {
                i++;
                printf("(18,:=)");
            }
            else
                printf("(17,:)");
            break;
        case ‘<‘:
            if(b==‘>‘)
            {
                i++;
                printf("(21,<>)");
            }
            else if(b==‘=‘)
            {
                i++;
                printf("(22,<=)");
            }
            else
                printf("(20,<)");
            break;
        case ‘>‘:
            if(b==‘=‘)
            {
                printf("(24,>=)");
                i++;
            }
            else
                printf("(23,>)");
            break;
        case ‘=‘:
            printf("(25,=)");
            break;
        case ‘;‘:
            printf("(26,;)");
            break;
        case ‘(‘:
            printf("(27,()");
            break;
        case ‘)‘:
            printf("(28,))");
            break;
        case ‘#‘:
            printf("(20,#)");
            break;
        default:
            {
            printf("\n存在字符 ‘%c‘，无法继续识别!\n",c);
            s=0;    //用s=0记录存在非法字符
            break;
            }
    }