daima.txt

自己编写的一个算法

词法分析器程序源代码


include <stdio.h>#include <string.h>#include <process.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 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("追查ZhuiCha.com网络技术 版权所有\n");
 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=="+"||currentchar=="-"||currentchar=="*"||currentchar=="/"||currentchar=="="||currentchar=="!"||currentchar=="&"||(ch=currentchar)=="\n"||currentchar==" "||currentchar=="["||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
 {printf("追查ZhuiCha.com网络技术 版权所有\n");

    arr[i++]="\0";
    fprintf(out,"%s%d,%c%s%c%s\n","(",15,""",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++]=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","(",15,""",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,"if")==0)
    fprintf(out,"%s%d,%c%s%c%s\n","(",0,""",arr,""",")");
    else if(strcmp(arr,"else")==0)
    fprintf(out,"%s%d,%c%s%c%s\n","(",1,""",arr,""",")");
    else if(strcmp(arr,"while")==0)
    fprintf(out,"%s%d,%c%s%c%s\n","(",2,""",arr,""",")");
    else if(strcmp(arr,"do")==0)
    fprintf(out,"%s%d,%c%s%c%s\n","(",3,""",arr,""",")");
 else
 fprintf(out,"%s%d,%c%s%c%s\n","(",14,""",arr,""",")");
}
while(currentchar==" ")
{ 
 currentchar=fgetc(in);
}
//判断标识符包括：+, -, *, /, (, ), {, }, <, >, ;, :, !=, >=, <=, ==, =.
if(currentchar=="+")
{
    fprintf(out,"%s%d,%c%c%c%s\n","(",9,""",currentchar,""",")");
    currentchar=fgetc(in);
}
while(currentchar==" ")
{ 
 currentchar=fgetc(in);
}
if(currentchar=="-")
{
 fprintf(out,"%s%d,%c%c%c%s\n","(",10,""",currentchar,""",")");
    currentchar=fgetc(in);
}
while(currentchar==" ")
{ 
 currentchar=fgetc(in);
}
if(currentchar=="*")
{
 fprintf(out,"%s%d,%c%c%c%s\n","(",11,""",currentchar,""",")");
    currentchar=fgetc(in);
}
while(currentchar==" ")
{ 
 currentchar=fgetc(in);
}