Help With K&Rs Counting Chars Example

问题

I'm working my way through K&R's 2nd edition, and I've been stumped with this seemingly simple example:

#include <stdio.h>

main(){
    double c;
    for(c = 0; ((getchar() != EOF) && (getchar() != '\n')); ++c)
        ;
    printf("%.0f\n",c);
}

It simply isn't working correctly. I added in the (getchar() != '\n') portion to end the program when I press enter, but that doesn't really help either.

Here's some sample output, using the gcc that comes with Mac OSX 10.6 dev tools.

pool-000:Desktop user$ ./a.out 
a
0
pool-000:Desktop user$ ./a.out 
asdf

2
pool-000:Desktop user$ ./a.out 
asfasf

3

So something is obviously wrong. I'm on page 18, if that helps. This isn't homework, this is for fun!

Thanks :)

回答1:

Each call to getchar() will wait for a character to be read, so you're reading more than you think per iteration of the loop.

Also, at least in my opinion, a counter is (almost) never a double, you should use an integer type such as plain old int.

回答2:

The problem with doing two "getchar()" operations is that you will read TWO get chars in the conditional test... before you get to the ++c.

Ditch the "EOF" comparison and it should work as you expect.

来源：https://stackoverflow.com/questions/1658436/help-with-krs-counting-chars-example