是时候问了？ [英] Time to ask?

问题描述

我还在K& R。


我正在写这个练习并碰壁。

这是代码全..（因为这通常是要求）。我的问题

是;


1）为什么打印4行而不是预期的2行？

2）我是使用X代码编译这个....不确定这是否有任何

与它有关。当我单步执行代码时，我会尽可能地将b $ b写入HANGS HERE。它不会再进一步​​了。我假设这2个
是否相关？或不？ ......但是，我觉得我需要一些更聪明的头脑。


提前谢谢./


#include< stdio.h>

#include< string.h>

#define MAXNUM 10

#define TESTCHAR ''T''


int getops（char s []）;

int main（）{

char s [ MAXNUM]，输入;

while（（type = getops（s））！= EOF）{

开关（类型）{


case''T''：

printf（"％s \ n"，s）;

休息;

}


}


返回0;

}

/ *** ** GETOPS ****** /


int getch（void）;

void ungetch（int c）;

int getops（char s []）{


int c，i;

while（（c = getch（））=='''' || c ==''\t''）;

for（i = 0; i< = 1; i ++）/ ***** HANGS HERE *** /

ungetch（''T''）;

}


/ ***** GETCH& UNGETCH ***** /


#define MAXBUFF 10

char buffer [MAXBUFF];

int buffp = 0;

int j = 1;

int getch（void）{

return（buffp 0）？ buffer [ - buffp]：getchar（）;


}


void ungetch（int c）{

printf（" Printing line％d \ nn"，j ++）;


}

/ ******


输出（输入p）：

>> / begin输出/<<

p

印刷线1

印刷线2

印刷线3

印刷线4

>> /输出结束/<< ;

** /

解决方案

int getops（char s []）{


int c，i;

while（（c = getch （））==''''|| c ==''\ t''）;

for（i = 0; i< = 1; i ++）/ **** * HANGS HERE *** /

ungetch（''T''）;

}

First我注意到的事情是getops没有返回任何东西。

这可能是问题吗？


MQ

mdh写道：

我还在K& R。


我在写这个练习的过程已经碰壁了。

这里是完整的代码..（因为这通常被要求）。我的问题

是;


1）为什么打印4行而不是预期的2行？

2）我是使用X代码编译这个....不确定这是否有任何

与它有关。当我单步执行代码时，我会尽可能地将b $ b写入HANGS HERE。它不会再进一步​​了。我假设这2个
是否相关？或不？ ......但是，我觉得我需要一些聪明的头脑来这个

点。


提前谢谢./

我冒昧地剪掉你的代码。你没有编码

的问题。你有一个理解问题。 getch（）和ungetch（）是

而不是标准C函数。它们可以实现为扩展。 Borland

和DJGPP浮现在脑海中，在conio.h中宣称并且肯定还有其他人。

他们不是标准C.


-

Joe Wright

所有东西都应尽可能简单，但并不简单。

---阿尔伯特爱因斯坦---

你没有编码

问题。你有一个理解问题。 getch（）和ungetch（）是

而不是标准C函数。

OP已实现这些功能。看一下

列表的底部。


MQ

I am still at K&R.

I am in the process of writing this exercise and have run into a wall.
Here is the code in full..( as this is usually asked for). My questions
are;

1) Why does it print 4 lines instead of the expected 2?
2) I am using X-code to compile this....not sure if this has anything
to do with it. When I step through the code, I get as far as where I
have written "HANGS HERE" and it goes no further. I am assuming these 2
are related? or not? ...But, I think I need some smarter minds at this
point.

Thanks in advance./

# include <stdio.h>
# include <string.h>
# define MAXNUM 10
# define TESTCHAR ''T''

int getops(char s[]);
int main (){
char s[MAXNUM], type;
while ( (type=getops(s)) != EOF){
switch (type) {

case ''T'':
printf("%s\n", s);
break;
}

}

return 0;
}
/*****GETOPS******/

int getch(void);
void ungetch(int c);
int getops(char s[]){

int c, i;
while ( (c = getch()) == '' '' || c ==''\t'');
for ( i=0; i <= 1; i++) /*****HANGS HERE***/
ungetch(''T'');
}


/***** GETCH & UNGETCH*****/

# define MAXBUFF 10
char buffer[MAXBUFF];
int buffp=0;
int j=1;
int getch(void){
return (buffp 0) ? buffer[--buffp]: getchar() ;

}

void ungetch(int c){
printf("Printing line %d\n", j++);

}
/******

Output("p" entered):

>>/beginning of output/<<

p
Printing line 1
Printing line 2
Printing line 3
Printing line 4

>>/end of output/<<

**/

解决方案

int getops(char s[]){

int c, i;
while ( (c = getch()) == '' '' || c ==''\t'');
for ( i=0; i <= 1; i++) /*****HANGS HERE***/
ungetch(''T'');
}

First thing I have noticed is that getops does not return anything.
Could this be the problem?

MQ

mdh wrote:

I am still at K&R.

I am in the process of writing this exercise and have run into a wall.
Here is the code in full..( as this is usually asked for). My questions
are;

1) Why does it print 4 lines instead of the expected 2?
2) I am using X-code to compile this....not sure if this has anything
to do with it. When I step through the code, I get as far as where I
have written "HANGS HERE" and it goes no further. I am assuming these 2
are related? or not? ...But, I think I need some smarter minds at this
point.

Thanks in advance./

I have taken the liberty of snipping your code. You don''t have a coding
problem. You have an Understanding problem. getch() and ungetch() are
not Standard C functions. They may be implemented as extensions. Borland
and DJGPP come to mind, declared in conio.h and there are surely others.
They are not Standard C.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

You don''t have a coding

problem. You have an Understanding problem. getch() and ungetch() are
not Standard C functions.

The OP has implemented these functions. Take a look at the bottom of
the listing.

MQ

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