>> ...you mean, you can take a string and make a stream that will read from 
>> it? (Or, presumably, write to it, if you desire.)
> 
>   Correct. Or, more precisely, you can write to an ostringstream and then
> get a regular string out of it (with the str() function).

Ah  - because a string is fixed-size once created?

>   Where this becomes fancy is when a function takes an std::istream or an
> std::ostream reference.
>   The functions themselves don't know (and don't need to know) what the
> exact type of stream actually is. All of them are used in the same way.
>   This is, in fact, pure object-oriented programming (all of those things
> are inherited from std::istream or std::ostream, so they can be given to
> those two functions). Beautiful.

OOP as it should be.

>> So what exactly do the good() and fail() functions do?
> 
> http://www.cplusplus.com/reference/iostream/ios/good.html
> http://www.cplusplus.com/reference/iostream/ios/fail.html
> 
>   Basically you can think of good() as "did the last read succeed?"
> (the most common reason for the stream to be not good() is EOF).
> It's an overall "is the stream still good?".
> 
>   And fail() as "did the input contain a value of the correct type?".
> In other words, with the "std::cin >> integer; if(std::cin.fail() ..."
> you are asking "did reading an integer fail?". The most common reason
> for fail() to be true is that input did not contain what was expected
> by the parameter (in this example an integer value).

OK... So good() is a property of the stream, and fail() is a property of 
the last thing read from it?

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