Re: C++ Primer ex 9.14
On Sep 17, 3:42 am, Barry <dhb2...@gmail.com> wrote:
James Kanze wrote:
On Sep 16, 1:02 pm, Erik Wikstr=F6m <Erik-wikst...@telia.com> wrote:
[...]
It runs fine. Is there any way I can replace what while loop with
std::copy ?
Might be, you would have to use std::istream_iterators and a back inse=
rt
iterator to add the elements to the vector, something like (untested):
std::copy(
std::istream_iterator<std::string>(std::cin),
std::istream_iterator<std::string>() // The same as end() for a str=
eam
std::back_insert_iterator<std::vector>(vec)
);
Even simpler would be to use the istream_iterators to initialize
the container. Something like:
std::vector< std::string > vec(
(std::istream_iterator< std::string >( std::cin )),
^ ^
if it's not for formatting, then it's
not necessary as std::cin is not a type,
I'm not sure. You may be right, because I don't think that
std::cin is a legal variable name in this context. But the more
frequent:
(std::istream_iterator< std::string >( input )),
does require them.
(std::istream_iterator< std::string >()) ) ;
(Note that the outermost parentheses around the arguments are
necessary to prevent the compiler from interpreting the
statement as a function declaration.)
and it's not a function declaration I think. As "TypeA ()" is
a function type who returns "TypeA". So if the compiler
wrongly interpret this way, then it will report that "passing
a type is illegal" (I just made this wording :-) )
it only happens to those with none parameter like the latter
one you wrote.
std::istream_iterator< std::string >()
would be a declaration---in the context of a function parameter,
it's the equivalent of:
std::istream_iterator< std::string >(*ptrToFnc)()
And while I think you're right for
std::istream_iterator< std::string >( std::cin ),
something like:
std::istream_iterator< std::string >( someFile ),
is definitely a declaration.
Technically, too, it should be sufficient to disambiguate any
one of the parameters; adding the parentheses to just one of the
parameters should suffice. But I've had problems with this in
the past, and have gotten into the habit of adding them more or
less systematically, whenever there might be an ambiguity.
(This is really something that needs fixing, although I don't
have a good solution. Imagine the poor beginner, who originally
writes the code without the extra parentheses, using std::cin,
and it works fine. He then replaces std::cin with a file, and
suddenly gets compiler errors when he tries to use vec, further
down in his code.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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