Re: [boost] [algorithm] to_lower_copy / to_upper_copy with no output param assumes sequence to be same as input

Subject: Re: [boost] [algorithm] to_lower_copy / to_upper_copy with no output param assumes sequence to be same as input
From: Sebastian Karlsson (sairony_at_[hidden])
Date: 2011-06-23 15:47:18

2011/6/23 Sebastian Karlsson <sairony_at_[hidden]>:
> 2011/6/23 Olaf van der Spek <ml_at_[hidden]>:
>> On Thu, Jun 23, 2011 at 1:26 PM, Sebastian Karlsson <sairony_at_[hidden]> wrote:
>>>>>                        OutputSequenceT Output( ::boost::begin( Input ), ::boost::end( Input ) );
>>>>
>>>> Doesn't this also do an unnecessary copy?
>>>>
>>>> Olaf
>>>
>>> It does, but it uses one less which as stated is a prime candidate for
>>> NRVO. The current approach needs one temporary for the return value as
>>> well as a temporary for argument conversion, which is basically only
>>> there to inform about the return type.
>>
>> OutputSequenceT Output( ::boost::begin( Input ), ::boost::end( Input ) );
>>
>> This one copies input to output. Then the function does case conversion.
>> The original (AFAIK) does the case conversion while copying from input
>> to output.
>>
>> Olaf
>
> That appears to be truth, that's only a flaw in my implementation
> though, I'll see if I can fix it :)
>
> Kind regards,
> Sebastian Karlsson
>

Seems to be easier than I anticipated, just add output type as a param
and slap it in as the return type for transform_range_copy, like so:

                template<typename SequenceT, typename OutputT >
                inline SequenceT to_lower_copy(
                        const SequenceT& Input,
                        const std::locale& Loc=std::locale())
                {
                        return ::boost::algorithm::detail::transform_range_copy< OutputT >(
                                Input,
                                ::boost::algorithm::detail::to_lowerF<
                                typename range_value<SequenceT>::type >(Loc));
                }

Seems to work with the little testing I've been able to do so far.

Kind regards,
Sebastian Karlsson