Re: [Adobe-source-devel] Problems with narrow

[Sean P. <sp...@ad...>]

>>>
>>>
>>>> std::istream::int_type    c_int(stream_m->get());
>>>> char                    c(0);
>>>>
>>>> c = std::use_facet<std::ctype<wchar_t> >(std::locale()).narrow 
>>>> (c_int, '?');
>>>>
>>>>
>>>>
>>>>
>>>
>>> In the cygwin gcc that I have (gcc 3.4.4) I get the following  
>>> error in the above line of code:
>>>
>>>
>>>
>>
>> I'm not sure where wchar_t is coming into play given that c is of  
>> type char.
>>
>>
>
> The reason I have to use wchar_t is because narrow's argument is of  
> type char_type, which in every case but the wchar_t one is just a  
> char, so narrow is a no-op (it would require a static_cast to fit  
> the parameter to the argument, at which point narrow is moot).
>

I understand - this is simply some confusion about how istream::get()  
works -

It returns either a character c or traits::eof() - the reason it  
returns an int_type is because traits::eof is always out-of-band for  
the character type (int_type is always larger than char_type). To  
recover the character use traits::to_char_type().

Sean



>
>
>
>>
>>
>>
>>>
>>>
>>>
>>>
>>>
>>>> Exception: St8bad_cast
>>>>
>>>>
>>>>
>>>>
>>>
>>> Has anyone seen this before? Any ideas of a possible workaround?  
>>> Anyone know of an easier (yet equally portable) means of  
>>> narrowing an int_type value from a stream::get()?
>>>
>>>
>>>
>>
>> char c (stream_m->narrow(c_int, '?'));
>>
>>
>
> See above.
>
>
>
>> Sean
>>
>>
>>
>>
>>
>>>
>>> Blessings,
>>> Foster
>>>
>>> --
>>> Foster T. Brereton              <}}}><              Romans 3:21-26
>>> A d o b e   S o f t w a r e   T e c h n o l o g y   L a b
>>> "What 99 percent of programmers need to know is not how to build
>>> components but how to use them." -- Alexander Stepanov
>>>
>>>
>>>
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>>>
>>
>>
>>
>>
>>
> --
> Foster T. Brereton              <}}}><              Romans 3:21-26
> A d o b e   S o f t w a r e   T e c h n o l o g y   L a b
> "What 99 percent of programmers need to know is not how to build
> components but how to use them." -- Alexander Stepanov
>
>
>
> -------------------------------------------------------
> SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
> from IBM. Find simple to follow Roadmaps, straightforward articles,
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