txt文件最后一位是什么？
（词法分析）源程序：
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <alloc.h>
#include <conio.h>
int IsLetter(char ch)
{/*判断是否是字母，是则返回 1，否则返回 0 */
if(isalpha(ch)) return 1;
return 0;
}
int IsDigit(char ch)
{/*判断是否为数字或字母，是则返回 1，否则返回 0 */
if(isalnum(ch)) return 1;
return 0;
}
int IsSpace(char ch)
{/*判断是否为空白符（空格、换行、制表符等）,是则返回 1，否则返回 0*/
if(isspace(ch)) return 1;
return 0;
}
void GetChar(FILE *fp,char *ch)
{/*读取字符送ch*/
*ch = fgetc(fp);
}
void GetBC(FILE *fp,char *ch)
{/*如果是空白则继续读下一个，直到不是空白*/
do {
GetChar(fp,ch);
}while(IsSpace(*ch)&&(*ch != EOF));
}
void Retract(FILE *fp,char *ch)
{/*光标回退一位,并使 ch 为空*/
fseek(fp,-1,1);
*ch = ' ';
}
char Reserve(char *strToken)
{/*返回关键字的编码*/
if(strcmp(strToken, "main ") == 0) return '2 ';
if(strcmp(strToken, "int ") == 0) return '1 ';
if(strcmp(strToken, "char ") == 0) return '3 ';
if(strcmp(strToken, "if ") == 0) return '4 ';
if(strcmp(strToken, "else ") == 0) return '5 ';
if(strcmp(strToken, "for ") == 0) return '6 ';
if(strcmp(strToken, "while ") == 0) return '7 ';
return '0 ';
}
void Concat(char *strToken, char *ch)
{/*将ch中的字符连接到strToken后面*/
int i;
for(i=0;i <80;i++) {
if(*strToken == NULL) {
*strToken = *ch;
break;
}
strToken++;
}
}
int lexSubFunc(FILE *fp1,FILE *fp2)
{/*词法分析子程序*/
char ch,code;
int i;
char strToken[80];
while(1) {
GetBC(fp1,&ch);
for(i=0;i <80;i++) strToken[i]=NULL;
if(ch == EOF) return 0;
if (IsLetter(ch)) {
while (IsLetter(ch) || IsDigit(ch)) {
Concat(strToken,&ch);
GetChar(fp1,&ch);
}
Retract(fp1,&ch);
code = Reserve(strToken);
if (code == '0 ') {
printf( "(10,%-6s)\n ",strToken);
fputs( "(10,\ " ",fp2); fputs(strToken,fp2); fputs( "\ ")\n ",fp2);
}
else {
printf( "(%2c,%-6s)\n ",code,strToken);
fputs( "( ",fp2); fputc(code,fp2);fputs( ",\ " ",fp2);fputs(strToken,fp2); fputs( "\ ")\n ",fp2);
}
}
else if (IsDigit(ch)) {
while (IsDigit(ch)) {
Concat(strToken,&ch);
GetChar(fp1,&ch);
}
Retract(fp1,&ch);
printf( "(20,%-6s> \n ",strToken);
fputs( "(20,\ " ",fp2); fputs(strToken,fp2); fputs( "\ ")\n ",fp2);
}
else if (ch == '= ') {
GetChar(fp1,&ch);
if(ch == '= '){
printf( "(39,==%3c)\n ", ' ');
fputs( "(39,\ "==\ ")\n ",fp2);
}
else{
Retract(fp1,&ch);
printf( "(21,=%5c)\n ", ' ');
fputs( "(21,\ "=\ ")\n ",fp2);
}
}
else if (ch == '+ ') {
printf( "(22,+%5c)\n ", ' ');
fputs( "(22,\ "+\ ")\n ",fp2);
}
else if (ch == '- ') {
printf( "(23,-%5c)\n ", ' ');
fputs( "(23,\ "-\ ")\n ",fp2);
}
else if (ch == '* ') {
printf( "(24,*%5c)\n ", ' ');
fputs( "(24,\ "*\ ")\n ",fp2);
}
else if (ch == '/ ') {
printf( "(25,/%5c)\n ", ' ');
fputs( "(25,\ "/\ ")\n ",fp2);
}
else if (ch == '( ') {
printf( "(26,(%5c)\n ", ' ');
fputs( "(26,\ "(\ ")\n ",fp2);
}
else if (ch == ') ') {
printf( "(27,)%5c)\n ", ' ');
fputs( "(27,\ ")\ ")\n ",fp2);
}
else if (ch == '[ ') {
printf( "(28,[%5c)\n ", ' ');
fputs( "(28,\ "[\ ")\n ",fp2);
}
else if (ch == ']} ') {
printf( "(29,]%5c)\n ", ' ');
fputs( "(29,\ "]\ ")\n ",fp2);
}
else if (ch == '{ ') {
printf( "(30,{%5c)\n ", ' ');
fputs( "(30,\ "{\ ")\n ",fp2);
}
else if (ch == '} ') {
printf( "(31,}%5c)\n ", ' ');
fputs( "(31,\ "}\ ")\n ",fp2);
}
else if (ch == ', ') {
printf( "(32,,%5c)\n ", ' ');
fputs( "(32,\ ",\ ")\n ",fp2);
}
else if (ch == ': ') {
printf( "(33,:%5c)\n ", ' ');
fputs( "(33,\ ":\ ")\n ",fp2);
}
else if (ch == '; ') {
printf( "(34,;%5c)\n ", ' ');
fputs( "(34,\ ";\ ")\n ",fp2);
}
else if (ch == '> ') {
GetChar(fp1,&ch);
if(ch == '= '){
printf( "(37,> =%4c)\n ", ' ');
fputs( "(37,\ "> =\ ")\n ",fp2);
}
else{
Retract(fp1,&ch);
printf( "(35,> %5c)\n ", ' ');
fputs( "(35,\ "> \ ")\n ",fp2);
}
}
else if (ch == ' < ') {
GetChar(fp1,&ch);
if(ch == '= '){
printf( "(38, <=%4c)\n ", ' ');
fputs( "(38,\ " <=\ ")\n ",fp2);
}
else{
Retract(fp1,&ch);
printf( "(36, <%5c)\n ", ' ');
fputs( "(36,\ " <\ ")\n ",fp2);
}
}
else if (ch == '! ') {
GetChar(fp1,&ch);
if(ch == '= '){
printf( "(40,!=%3c)\n ", ' ');
fputs( "(40,\ "!=\ ")\n ",fp2);
}
else
Retract(fp1,&ch);
}
else if (ch == '\0 ') {
printf( "(1000,\0%3c)\n ", ' ');
fputs( "(1000,\ "\0\ ")\n ",fp2);
}
}
}
void main()
{/*主程序*/
FILE *fp1,*fp2;
if((fp1=fopen( "input.txt ", "rt "))==NULL)
{
printf( "Cannot open input.txt\n ");
getch(); exit(1);
}
if((fp2=fopen( "out.txt ", "wt+ "))==NULL)
{
printf( "Cannot create out.txt FILE.strike any key exit ");
getch(); exit(1);
}
lexSubFunc(fp1,fp2);
fclose(fp1);
fclose(fp2);
getch();
}
如果input.txt文件内容为:{9*a
运行后进入死循环（注意a后面没有空格）
如果input.txt文件内容为:{9*a}
运行后程序可以正常结束。
同样是当ch==EOF是退出的，为什么第一种就退不了呢?
各位GGJJ帮我看看啊
谢谢了
[解决办法]
char类型的一个标志
char buf;
buf = fgetc(fp);
if(buf == EOF)
{
文件结束
}
[解决办法]
fopen( "input.txt ", "rt ")改成fopen( "input.txt ", "rb ")试试，你那是以文本方式打开的。
[解决办法]
txt有最后一位吗?
应该没有
判断文件结束用 EOF 但是它不是文件的字符,只是一个错误标识,是读过最后一个字符,再读下一个字符时返回的错误
