Re: IO problem
On 2/19/2014 9:29 AM, nvangogh wrote:
I have come to a question in C++ Primer (p 314 , exercise 8.1) that is
not clear to me.
"Write a function that takes and returns an istream&. The function
should read the stream until it hits end-of-file. The function should
print what it reads to the standard output. Reset the stream so that it
is valid before returning the stream."
Breaking this down, the function has to do three things:
1. Read a stream until it hits end-of-file
So the >> operator reads input from an istream object - cin.
This stream's end of file can be interrogated by
cin.eof(). This returns true if the end of file bit is set which can be
tested with a bool variable
bool on = false;
on = cin.eof();
if(on == true)
// end of file is reached, else
if(on ==false)
// keep reading cin
I don't believe that this is completely correct so can someone show me
how this code should be presented?
There has to be something after the 'if' and its condition to designate
the action that shall be taken when the condition is met. So, instead
of the comments ("// end of file is reached") put something there so
that the program takes the action you want it to take. Same for the
other condition.
Usually, if you only have a "either-or" situation (like in your case,
it's either the end of file or not), then there is no need for the
second 'if', a simple 'else' ought to do. Something *like*
if (on)
...
else
...
(put the proper action instead of the ellipsis)
2. Print what is read to the standard output
I can only imagine this to be cout << ? But am lost from here
Yes, that's pretty much what you need to do.
3. Reset the stream so it is valid before returning the stream
This section of the problem again defeats me.
std::cin.clear();
resets the error condition on the 'std::cin' stream.
Can anyone help with this function?
Part of the answer can also be found in the FAQ, section 5, question 2,
if memory serves.
V
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