postfix operator++(int) with const

[Chris Forone]

hello group,

why i cant make the InputIterator of the following func-temp const?

template<typename InputIterator, typename OutputIterator>
OutputIterator Types::Copy(InputIterator source,
OutputIterator first, OutputIterator last)
{
while (first != last)
*first++ = *source++;

return last;
}

thanks & hand, chris

[Road.Tang]

On Jun 20, 4:01 pm, Chris Forone <[e-mail]:

hello group,

why i cant make the InputIterator of the following func-temp const?

template<typename InputIterator, typename OutputIterator>
OutputIterator Types::Copy(InputIterator source,
OutputIterator first, OutputIterator last)
{
while (first != last)
*first++ = *source++;

return last;

}

thanks & hand, chris

Not very understand what you mean.

and, note one of the standard copy declaration is
template<typename In, typename Out>
Out copy(In first, In last, Out res)

-road

[Federico Zenith]

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Chris Forone wrote:

hello group,

why i cant make the InputIterator of the following func-temp const?

[...]
*first++ = *source++;

^^

[...]

You are post-incrementing the "source" variable, so it obviously cannot
be constant. If you need it to be const for whatever reason (eg. someone
else wrote the header and you cannot change it), just make a copy of it
(assuming the InputIterator::operator= is defined and works as expected):

InputIterator sourceCopy = source;
while (first != last)
*first++ = *sourceCopy++;

Otherwise, passing by value as in your current implementation is just fine.

I suppose, though, that you meant "const" as "iterator cannot be used to
change pointed value". I'm afraid you have to define a
ConstInputIterator for that.

Cheers,
- -Federico
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[Chris Forone]

Federico Zenith schrieb:

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Chris Forone wrote:

>hello group,

why i cant make the InputIterator of the following func-temp const?

[...]
*first++ = *source++;

^^

>[...]

You are post-incrementing the "source" variable, so it obviously cannot
be constant. If you need it to be const for whatever reason (eg. someone
else wrote the header and you cannot change it), just make a copy of it
(assuming the InputIterator::operator= is defined and works as expected):

InputIterator sourceCopy = source;
while (first != last)
*first++ = *sourceCopy++;

Otherwise, passing by value as in your current implementation is just fine.

I suppose, though, that you meant "const" as "iterator cannot be used to
change pointed value". I'm afraid you have to define a
ConstInputIterator for that.

Cheers,
- -Federico
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thanks a lot, thats it!

cheers, chris

[Chris Forone]

Road.Tang schrieb:

On Jun 20, 4:01 pm, Chris Forone <[e-mail]:

>hello group,

why i cant make the InputIterator of the following func-temp const?

template<typename InputIterator, typename OutputIterator>
OutputIterator Types::Copy(InputIterator source,
OutputIterator first, OutputIterator last)
{
while (first != last)
*first++ = *source++;

return last;

}

thanks & hand, chris

Not very understand what you mean.

and, note one of the standard copy declaration is
template<typename In, typename Out>
Out copy(In first, In last, Out res)

-road

i know the std::copy in std::algorithm. i need a target-limited version
to copy with streambuf_iterator to std::valarray in multiple steps...

cheers, chris

[James Kanze]

On Jun 20, 10:01 am, Chris Forone <[e-mail]:

why i cant make the InputIterator of the following func-temp
const?

template<typename InputIterator, typename OutputIterator>
OutputIterator Types::Copy(InputIterator source,
OutputIterator first, OutputIterator last)
{
while (first != last)
*first++ = *source++;
return last;
}

Because you modify it in the function. You can instantiate the
algorithm with const_iterator, however, if that's what you want.

--
James Kanze (GABI Software) email:ja*********@gmail.com
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