cifa.c

词法分析器

#include <stdio.h>
#include <string.h>
#define MAX 50
void 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 shuruchar;/*shuruchar存放当前输入字符*/
int i=0;/*arr数组的一个指针*/
char ch;
/*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
shuruchar=fgetc(in);
while(shuruchar==' ')
{ shuruchar=fgetc(in);}
while(shuruchar!='#')
{
/*常数部分判断*/
if((shuruchar>='a'&&shuruchar<='z')||(shuruchar>='A'&&shuruchar<='Z')||(shuruchar>='0'&&shuruchar<='9')||shuruchar=='('||shuruchar==')'||shuruchar=='{'||shuruchar=='}'||shuruchar=='>'||shuruchar=='<'||shuruchar==';'||shuruchar==':'||shuruchar=='+'||shuruchar=='-'||shuruchar=='*'||shuruchar=='/'||shuruchar=='='||shuruchar=='!'||shuruchar=='&'||(ch=shuruchar)=='\n'||shuruchar==' '||shuruchar=='['||shuruchar==']')
{
i=0;//清空arr字符数组
if(shuruchar>='0'&&shuruchar<='9')
{
 arr[i++]=shuruchar;
    shuruchar=fgetc(in);//再读入下一个字符
    while(shuruchar>='0'&& shuruchar<='9')
 {
    arr[i++]=shuruchar;
    shuruchar=fgetc(in);
 }
    if(shuruchar!='.')//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%c%s%c\n","数字输出:",'"',arr,'"');//格式化输出到目标文件，15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++]=shuruchar;
    shuruchar=fgetc(in);
    while(shuruchar>='0'&&shuruchar<='9')
 {
    arr[i++]=shuruchar;
    shuruchar=fgetc(in);
 }
    arr[i++]='\0';
    fprintf(out,"%s%d,%c%s%c%s\n","(",15,'"',arr,'"',")");
 }
    while(shuruchar==' ')
 { 
 shuruchar=fgetc(in);
 }
}
/*判断标识符和关键字部分*/
if((shuruchar>='a'&&shuruchar<='z')||(shuruchar>='A'&&shuruchar<='Z'))
{
  i=0;//清空arr字符数组
    while((shuruchar>='a'&&shuruchar<='z')||(shuruchar>='0'&&shuruchar<='9')||(shuruchar>='A'&&shuruchar<='Z'))
 {
    arr[i++]=shuruchar;
    shuruchar=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,"if")==0||strcmp(arr,"int")==0||strcmp(arr,"while")==0||strcmp(arr,"do")==0||strcmp(arr,"else")==0||strcmp(arr,"do")==0||strcmp(arr,"main")==0||strcmp(arr,"void")==0||strcmp(arr,"float")==0||strcmp(arr,"char")==0
		||strcmp(arr,"double")==0||strcmp(arr,"break")==0||strcmp(arr,"long")==0||strcmp(arr,"case")==0||strcmp(arr,"default")==0||strcmp(arr,"goto")==0||strcmp(arr,"for")==0||strcmp(arr,"continue")==0||strcmp(arr,"switch")==0
		||strcmp(arr,"return")==0||strcmp(arr,"short")==0||strcmp(arr,"union")==0||strcmp(arr,"typedef")==0)
    fprintf(out,"%s%c%s%c\n","关键字：",'"',arr,'"');
 else
 fprintf(out,"%s%c%s%c\n","变量：",'"',arr,'"');
 if(arr[i]==arr[i+1])
 {/*j=arr[i];
  arr[i]=arr[i+1];*/
  arr[i+1]==' ';
 }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
//判断标识符包括：+, -, *, /, (, ), {, }, <, >, ;, :, !=, >=, <=, ==, =.
if(shuruchar=='+'||shuruchar=='-'||shuruchar=='*'||shuruchar=='/'||shuruchar==';'||shuruchar=='{'||shuruchar=='}'||shuruchar=='['||shuruchar==']'||shuruchar=='('||shuruchar==')'||shuruchar=='&')
{
 fprintf(out,"%s%c%c%c\n","标识符：",'"',shuruchar,'"');
    shuruchar=fgetc(in);
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
if(shuruchar=='=')
{
 i=0;
 arr[i++]=shuruchar;
 shuruchar=fgetc(in);
 if(shuruchar=='=')
 {
  arr[i++]=shuruchar;
  arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","等于：",'"',arr,'"');
     shuruchar=fgetc(in);
 }
 else
 { arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","赋值：",'"',arr,'"');
    }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
if(shuruchar==':')
{
 i=0;
 arr[i++]=shuruchar;
 shuruchar=fgetc(in);
 if(shuruchar==':')
 {
  arr[i++]=shuruchar;
  arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","冒号：",'"',arr,'"');
     shuruchar=fgetc(in);
 }
 else
 { arr[i++]='\0';
  fprintf(out,"%s%d,%c%s%c%s\n","(",16,'"',arr,'"',")");
    }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
if(shuruchar=='>')
{
 i=0;
 arr[i++]=shuruchar;
 shuruchar=fgetc(in);
 if(shuruchar=='=')
 {
  arr[i++]=shuruchar;
  arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","大于等于：",'"',arr,'"');
     shuruchar=fgetc(in);
 }
 else
 { arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","小于",'"',arr,'"');
    }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
if(shuruchar=='<')
{
 i=0;
 arr[i++]=shuruchar;
 shuruchar=fgetc(in);
 if(shuruchar=='=')
 {
  arr[i++]=shuruchar;
  arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","小于等于：",'"',arr,'"');
     shuruchar=fgetc(in);
 }
 else
 { arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","小于：",'"',arr,'"');
    }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
if(shuruchar=='!')
{
 i=0;
 arr[i++]=shuruchar;
 shuruchar=fgetc(in);
 if(shuruchar=='=')
 {
  arr[i++]=shuruchar;
  arr[i++]='\0';
  fprintf(out,"%s%c%s%c\n","不等于：",'"',arr,'"');
     shuruchar=fgetc(in);
 }
}
while(shuruchar==' ')
{ 
 shuruchar=fgetc(in);
}
while((ch=shuruchar)=='\n')
{
 shuruchar=fgetc(in);
}
 while(shuruchar==' ')
{
 shuruchar=fgetc(in);
}
}
else
{
 fprintf(out,"%s,%c%c%c\n","error",'"',shuruchar,'"');
    shuruchar=fgetc(in);
}
}//结束开头while语句
/*关闭文件退出*/
fclose(in);
fclose(out);
}