词法分析器//此程序读取infile.txt文件的信息进行词法分析，相应分析结果写入到自动生成的outfile.txt文件中#include
#include #include #define MAX 50void main(){FILE *in,*out;/*存放输入字符串和输出单词串的文件*/char arr[MAX];/*arr数组存放单词符号*/char currentchar;/*currentchar存放当前输入字符*/int i=0;/*arr数组的一个指针*//*以读方式打开输入文件*/if((in=fopen("infile.txt","r"))==NULL){ printf("can not open file\n"); exit(0);}/*以写方式打开输出文件*/if((out=fopen("outfile.txt","w"))==NULL){ printf("cannout open outfile\n"); exit(1);}//去掉开头空格currentchar=fgetc(in);while(currentchar==' '){ currentchar=fgetc(in);}int ch;
while(currentchar!='@'){/*常数部分判断*/if((currentchar>='a'&¤tchar<='z')||(currentchar>='A'&¤tchar<='Z')||(currentchar>='0'&¤tchar<='9')||currentchar=='>'||currentchar=='<'||currentchar==';'||currentchar==':'||currentchar=='+'||currentchar=='-'||currentchar=='*'||currentchar=='/'||currentchar=='='||(ch=currentchar)=='\n'||currentchar==' '){i=0;//清空arr字符数组if(currentchar>='0'&¤tchar<='9'){ arr[i++]=currentchar; currentchar=fgetc(in);//再读入下一个字符 while(currentchar>='0'&¤tchar<='9') { arr[i++]=currentchar; currentchar=fgetc(in); } if(currentchar!='.')//如果当前读入的符号不为小数点，则常数读完毕，输出此常数 { arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",11,'"',arr,'"',")");//格式化输出到目标文件,11代表种别码， arr为内码值，规定用数字本身代表 } else//当前字符为小数点则继续向下读入 { arr[i++]=currentchar; currentchar=fgetc(in); while(currentchar>='0'&¤tchar<='9') { arr[i++]=currentchar; currentchar=fgetc(in); } arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",11,'"',arr,'"',")"); } while(currentchar==' ') { currentchar=fgetc(in); }}/*判断标识符和关键字部分*/if((currentchar>='a'&¤tchar<='z')||(currentchar>='A'&¤tchar<='Z')){i=0;//清空arr字符数组 while((currentchar>='a'&¤tchar<='z')||(currentchar>='0'&¤tchar<='9')||(currentchar>='A'&¤tchar<='Z')) { arr[i++]=currentchar; currentchar=fgetc(in); }//把字符数组arr和关键字表比较，判断单词串是关键字还是标识符 arr[i++]='\0'; if(strcmp(arr,"begin")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",1,'"',arr,'"',")"); else if(strcmp(arr,"end")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",2,'"',arr,'"',")"); else if(strcmp(arr,"if")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",3,'"',arr,'"',")");
else if(strcmp(arr,"then")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",4,'"',arr,'"',")"); else if(strcmp(arr,"else")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",5,'"',arr,'"',")"); else if(strcmp(arr,"while")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",6,'"',arr,'"',")"); else if(strcmp(arr,"do")==0) fprintf(out,"%s%d,%c%s%c%s\n","(",7,'"',arr,'"',")"); else fprintf(out,"%s%d,%c%s%c%s\n","(",10,'"',arr,'"',")");}while(currentchar==' '){ currentchar=fgetc(in);}//判断标识符包括：+, -, *, /, (, ), {, }, <, >, ;, :, !=, >=, <=, ==, =.if(currentchar=='+'){ fprintf(out,"%s%d,%c%c%c%s\n","(",13,'"',currentchar,'"',")"); currentchar=fgetc(in);}while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar=='-'){ fprintf(out,"%s%d,%c%c%c%s\n","(",14,'"',currentchar,'"',")"); currentchar=fgetc(in);}while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar=='*'){ fprintf(out,"%s%d,%c%c%c%s\n","(",15,'"',currentchar,'"',")"); currentchar=fgetc(in);}while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar=='/'){ fprintf(out,"%s%d,%c%c%c%s\n","(",16,'"',currentchar,'"',")"); currentchar=fgetc(in);}
while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar=='<'){ i=0; arr[i++]=currentchar; currentchar=fgetc(in); if(currentchar=='=') { arr[i++]=currentchar; arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",17,'"',arr,'"',")"); currentchar=fgetc(in); } else if(currentchar=='>') { arr[i++]=currentchar; arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",18,'"',arr,'"',")"); currentchar=fgetc(in); } else { arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",19,'"',arr,'"',")"); }}
while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar==':'){ i=0; arr[i++]=currentchar; currentchar=fgetc(in); if(currentchar=='=') { arr[i++]=currentchar; arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",22,'"',arr,'"',")"); currentchar=fgetc(in); } else { arr[i++]='\0'; fprintf(out,"%s%d,%c%s%c%s\n","(",21,'"',arr,'"',")"); }}
while(currentchar==' '){ currentchar=fgetc(in);}if(currentchar==';'){ fprintf(out,"%s%d,%c%c%c%s\n","(",23,'"',currentchar,'"',")"); currentchar=fgetc(in);}
while(currentchar==' '){ {需要全部代码请联系QQ3710167 currentchar=fgetc(in);} while(currentchar==' '){ currentchar=fgetc(in);}}else{ fprintf(out,"%s,%c%c%c\n","error",'"',currentchar,'"'); currentchar=fgetc(in);}
}//结束开头while语句/*关闭文件退出*/fclose(in);fclose(out);printf("相应的词法分析结果在自动生成的outfile.txt文件中\n");}输出结果：infile:avgfgvf+b;<=@
outfile:(10,"avgfgvf")(13,"+")(10,"b")(23,";")(17,"<=")
