Re: A question about '=='' in C++!

On 21 Sep 2007 05:15:35 GMT, Guofu Chen wrote:
> Can anyone tell me the different between
> (1)
> int i, j;
> i = j ==1;
> cout << i << ' ' << j;
> and
> (2)
> int i, j;
> i = j = 1;
> cout << i << ' ' << j;
>
> Why the result of  (1) is
> 0 0
>
> while the result of (2) is
> 1 1

You are asking about C++, but yet you are posting in a C group.
You should post in a C++ group if you have C++ questions.
I set the followups.

Anyway, the difference between
 i = j == 1;
and
 i = j = 1;
is that in the first case, you are evaluating the expression
 j == 1, and assigning the result of that expression to i,
and in the second case, you are evaluating the expression
 j = 1, and assigning the result of that expression to i.

j == 1 compares whether j equals to 1, and yields 0 or 1 depending
whether it equaled or not. j is not modified.

j = 1 assigns the value 1 into j.

That is the difference. This is definitely covered in
your C++ study book, you should read it more carefully.

Incidentally, in your first exerpt, the code can actually output
anything for the value of j, because j is never initialized.
It can contain any arbitrary value.

-- 
Joel Yliluoma - http://bisqwit.iki.fi/
: comprehension = 1 / (2 ^ precision)
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