【编译】词法分析器【阴漾吧】

主程序 yang95.c 如下：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define null 0

int i,j,flag,status,count,id,row=1;
char ch,*tmpStr='\0';
char words[10] = {" "};
char program[1000];
FILE *input,*output,*fpReserver,*fpCal,*fpSep;

int Scan(char program[]){
  flag=-1;
  j=0;
  ch=program[i++];

  if((ch==' ')||(ch=='\n'||(ch=='\t'))&&ch!=EOF) {
    if(ch=='\n')
        row++;
    Scan(program);
  }
  else{
    /*判断是否保留字*/
    if((ch>='a')&&(ch<='z')){
        while(((ch>='a')&&(ch<='z'))||((ch>='0')&&(ch<='9'))){
            words[j++]=ch;
            ch=program[i++];
        }
        i--;
        words[j++]='\0';

        /*打开关键字文件*/
        if((fpReserver=fopen("keywords.txt","r"))==NULL){
            printf("file open in readonly mode,but an error generate!\n");
            exit(0);
        }
        while(fscanf(fpReserver,"%s",tmpStr)!=EOF)
          if(strcmp(words,tmpStr)==0){
            fclose(fpReserver);
            id++;
            flag=1;
            break;
          }
        fclose(fpReserver);
        if(flag==-1){
            id++;
            flag=2;
        }
    }/*end:判断是否保留字*/

    /*识别数字*/
    else if(isdigit(ch)){
        while(isdigit(ch)){/*都为数字时*/
            words[j++]=ch;
            ch=program[i++];
        }
        if(ch=='.'){ /*第一个小数点时  加入  且读取下一个字符*/
            words[j++]=ch;
            ch=program[i++];
            if(isdigit(ch)){
                while(isdigit(ch)){/*小数点后是数字则加入，读取下一个*/
                    words[j++]=ch;
                    ch=program[i++];
                }
                if(isalpha(ch)||(ch=='.')){/*如：22.2后面又出现小数点或字母*/
                    words[j++]=ch;
                    ch=program[i++];
                    while(isalpha(ch)||isdigit(ch)||ch=='.'){
                        words[j++]=ch;
                        ch=program[i++];
                    }
                    words[j]='\0';
                    id++;
                    flag=0;
                }
                else{/*数字、其他字符或结束符时，则为数据*/
                    words[j]='\0';
                    id++;
                    flag=3;
                }
            }
            else{/*小数点后不是数字*/
                while((ch!=' '&&ch!='\t'&&ch!='\n')&&ch!=EOF){
                    words[j++]=ch;
                    ch=program[i++];
                }
                words[j]='\0';
                id++;
                flag=0;
            }
        }
        else if(isalpha(ch)){ /*数字后是字母*/
            while(isdigit(ch)||isalpha(ch)||ch=='.'){
                words[j++]=ch;
                ch=program[i++];
            }
            words[j]='\0';
            id++;
            flag=0;
        }
        else if(!isalpha(ch)||ch!='.'){/*都为数字*/
            words[j]='\0';
            id++;
            flag=3;
        }
        i--;
    }/*end判断是否数字*/

    /*判断是否运算符*/

送TA礼物

1楼2008-05-21 18:37回复

    else switch(ch){
        case '=':{
            if (ch == '=')
                words[j++] = ch;
            words[j] = '\0';
            ch = program[i++];
            if (ch == '='){
                words[j++] = ch;
                words[j] = '\0';
            }
            else {
                i--;
            }
            id++;
            flag=4;
            break;
        }
        case'+':{
            if (ch == '+')
                words[j++] = ch;
            words[j] = '\0';
            ch = program[i++];
            if (ch == '='){
                words[j++] = ch;
                words[j] = '\0';
            }
            else if (ch == '+'){
                words[j++] = ch;
                words[j] = '\0';
            }
            else{
                i--;
            }
            id++;
            flag=4;
            break;
        }
        case'-':{
            if (ch == '-')
                words[j++] = ch;
            words[j] = '\0';
            ch = program[i++];
            if (ch == '='){
                words[j++] = ch;
                words[j] = '\0';
            }
            else if( ch == '-'){
                words[j++] = ch;
                words[j] = '\0';
            }
            else{
                i--;
            }
            id++;
            flag=4;
            break;
        }
        case'*':{
            if (ch == '*')
                words[j++] = ch;
            words[j] = '\0';
            ch = program[i++];
            if (ch == '='){
                words[j++] = ch;
                words[j] = '\0';
                flag=4;
            }
            else if (ch == '/'){
                words[j++] = ch;
                words[j] = '\0';
                flag=5 ;
            }
            else{
                i--;
                flag=4;
            }
            id++;
            break;
        }
        case'/':{
            /*if (ch == '/')*/
                words[j++] = ch;
            words[j] = '\0';
            ch = program[i++];
            if (ch == '='){
                words[j++] = ch;
                words[j] = '\0';
                flag=4;
            }
            else if (ch == '*'){
                words[j++] = ch;
                words[j] = '\0';
                ch=program[i++];
                flag=5;
                while(ch!='*')
                    ch=program[i++];
                i--;
            }
            else if(ch=='/'){
                words[j++] = ch;
                words[j] = '\0';
                flag=0;
            }
            else{
                i--;
                flag=4;
            }
            id++;
            break;
        }
        case '>': case '<':{
            if((ch=='<')||(ch=='>')){
                words[j++]=ch;
            }
            words[j]='\0';
            ch=program[i++];
            if(ch=='='){
                words[j++]=ch;
                words[j]='\0';
            }
            else
                i--;
            id++;
            flag=4;
            break;
        } /*end:运算符 < > <= >=*/
        case '!':{
            if(ch=='!'){
                words[j++]=ch;
            }
            words[j]='\0';
            ch=program[i++];
            if(ch=='='){
                words[j++]=ch;
                words[j]='\0';
                id++;
                flag=4;
            }/*!=*/
            else{
                i--;/*没有这句，'!='不会出现*/
                id++;
                flag=0;
            }
            break;
        } /*end:运算符 != */
        case ',':case ';':case '{':case '}':case '(':case ')':{
            words[j++]=ch;
            words[j]='\0';
            ch=program[i];
            id++;
            flag=5;
            break;
        }/*end:分隔符 */
        case -1:{
            flag=-1;
            break;
        }/*一定要加这句否则死循环*/
        default:{
            words[j++]=ch;
            words[j]='\0';
            id++;
            flag=0;
            break;
        }/* 其他符号*/
    }/*end:switch*/
  }/*end:else*/
  return flag;/*注意要放对位子*/
}

main()
{
    i=0;
    if((input=fopen("myInput.txt","r"))==null){
        printf("不能读取文件！");
        exit(0);
    }
    if((output=fopen("myOutput.txt","w+"))==null){
        printf("输出文件建立错误!");
        exit(0);
    }
    ch=fgetc(input);

    if((ch==' '||ch=='\n'||ch=='\t')&&ch!=EOF){
        if(ch=='\n')
            row++;
        ch=fgetc(input);
    }
    program[i++]=ch;

    do{
        ch=fgetc(input);
        program[i++]=ch;
    }while(ch!=EOF);
    program[i--]='\0';
    i=0;
    do{
        flag=Scan(program);
        if(flag==0)
            fprintf(output," %d  \t%d \t( error,\t' %s '\t)\n",row,id,words);
        else if(flag!=-1)
            fprintf(output," \t %d \t( %d,\t' %s '\t)\n",id,flag,words);
    }while (flag != -1) ;
    fclose(input);
    fclose(output);
}

2楼2008-05-21 18:37

存放保留字的文件 keywords.txt的内容如下：

auto double int struct break else long switch case enum register typedef char extern return union const float short unsigned continue for signed void default goto sizeof volatile do if while static

3楼2008-05-21 18:38

假设输入文件 myInput.txt 内容如下：

void main()/*yang*/
{

int a1,a2;
a1+=22.2;@
}

4楼2008-05-21 18:39

则输出文件 MYOUTPUT.txt内容如下：

1 ( 1, ' void ' )
2 ( 2, ' main ' )
3 ( 5, ' ( ' )
4 ( 5, ' ) ' )
5 ( 5, ' /* ' )
6 ( 5, ' */ ' )
7 ( 5, ' { ' )
8 ( 1, ' int ' )
9 ( 2, ' a1 ' )
10 ( 5, ' , ' )
11 ( 2, ' a2 ' )
12 ( 5, ' ; ' )
13 ( 2, ' a1 ' )
14 ( 4, ' += ' )
15 ( 3, ' 22.2 ' )
16 ( 5, ' ; ' )
6 17 ( error, ' @ ' )
18 ( 5, ' } ' )

5楼2008-05-21 18:40

提示：yang95.c、keywords.txt、myInput.txt三个文件必须在同一个文件夹中，且最好不要置于桌面上�

6楼2008-05-21 18:41

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