Re: How to read a 8-bit grayscale JPEG image using C++?

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 20 Jul 2007 15:07:41 -0000
Message-ID:
<1184944061.109647.277340@n60g2000hse.googlegroups.com>
On Jul 20, 3:16 am, "BobR" <removeBadB...@worldnet.att.net> wrote:

Kai-Uwe Bux <jkherci...@gmx.net> wrote in message...


    [...]

  buffer the_buf ( std::istreambuf_iterator<char>( infile ),
                   (std::istreambuf_iterator<char>() ) );
                  ^^^ ^^^

What you wrote is parsed as a function declaration.


Not after the correct *_iterator got 'called' with '.rdbuf()'.


Not a question of the "correct" iterator: istreambuf_iterator
has a constructor which takes an istream, as well as one which
takes a streambuf. The problem is that:

    std::istreambuf_iterator< char >( infile )

can be interpreted as a declaration, and when something can be
interpreted as a declaration, it is. And if what looks like
arguments to us are in fact declarations, then the above
declares a function. Putting in the extra pair of parentheses
creates a context where a declaration (of a function parameter)
is not legal, so it isn't interpreted as a declaration, but as
an expression to be passed to the constructor, and we have a
data definition, rather than a function declaration.

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James Kanze (GABI Software) email:james.kanze@gmail.com
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