The name of the function, not_eof, is confusing beacuse it suggests being a
test.  It is not a test and the proper usage pattern is

if(traits_type::not_eof(c) == c)

instead of

if(traits_type::not_eof(c))

It is a mistake easy to commit and it can cause runtime errors.

Chris


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Christopher Yeleighton wrote:
> It is not a test and the proper usage pattern is
>
> if(traits_type::not_eof(c) == c)

Nope. If you want to use 'not_eof()' to test for "EOF" you would do
it like this:

  if (traits_type::eq_int_type(traits_type::not_eof(c), c))
    ...

However, this is not the intention of 'not_eof()'. The use of this
function is to signal success on return, i.e. it is used like this:

  int_type overflow(int_type c)
  {
     // whatever overfow() has to do
     return traits_type::not_eof(c);
  }

That is, 'not_eof()' is intended to conjure up a character, i.e. an
'int_type' value different from 'traits_type::eof()', even if the
argument 'c' is actually 'traits_type::eof()'. If you want to test
for "EOF" you would use

  if (traits_type::eq_int_type(traits_type::eof(), c))
    ...

. or a corresponding negation of the above expression.
--
<mailto:dietmar_kuehl@yahoo.com> <http://www.dietmar-kuehl.de/>
<http://www.eai-systems.com> - Efficient Artificial Intelligence

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