Re: [boost] Spurious warning in lexical_cast.hpp

From: Paul A Bristow (pbristow_at_[hidden])
Date: 2006-08-09 12:22:08

Joh Maddock tells me you are concerned that the maxdigits_10 magic formula
doesn't work with base other than 2.

This is obviously entirely true, but decimal based C++ as rare as hens
teeth?

So it is seems hardly worth an extra test of numeric_limits<>::radix in
every invocation of lexical_cast that I fear cannot be optimised away until
C++0X hits the streets (and can be relied upon in every compiler).

(Unless if can be done with a macro - but then there is a problem with it
being standard).

So I'd leave a comment, and put the problem in the 'too difficult' drawer
for now?

Thanks for your work on this nonetheless.

Paul

---
Paul A Bristow
Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
[phone] & SMS, Mobile [phone] & SMS
pbristow_at_[hidden]
 
 
|  -----Original Message-----
|  From: boost-bounces_at_[hidden] 
|  [mailto:boost-bounces_at_[hidden]] On Behalf Of Gennaro Prota
|  Sent: 04 August 2006 18:40
|  To: boost_at_[hidden]
|  Subject: Re: [boost] Spurious warning in lexical_cast.hpp
|  
|  On Fri, 4 Aug 2006 14:33:30 +0100, "Paul A Bristow"
|  <pbristow_at_[hidden]> wrote:
|  
|  >IMO, it does NOT require IEEE754 - it only requires
|  >numeric_limits<T>::digits to be correct for that type T.
|  >
|  >So, it works for NTL quad_float which is NOT IEEE754.
|  
|  That's what I was wishing to hear :-)
|  
|  >|  As to the docs, this is what I would add. Feedback welcome.
|  >|  
|  >|   lexical_cast<> offers the following guarantees: [...]
|  >|
|  >Well in principle yes, but the C++ Standard is not clear if 
|  the second is
|  >REQUIRED, or is just a Good Quality Implementation.
|  
|  Hmm... what about "lexical_cast<> requires a good quality
|  implementation"? ;-) Seriously, I'll take some time for writing good
|  unit tests, so that we can have a clear view of what happens.
|  
|  This looks like a very sound addition to me. If it proves so in
|  practice I guess Beman can add it to the standard proposal.
|  
|  --
|  [ Gennaro Prota, C++ developer for hire ]
|  
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