Re: [boost] [review] string convert

Subject: Re: [boost] [review] string convert
From: Vladimir Batov (vbatov_at_[hidden])
Date: 2011-05-05 19:58:44

> Matthew Chambers <matt.chambers42 <at> gmail.com> writes:
> 
> Did you ever use boost.convert on a non-defaultable type? I've never needed
> that.

It might come a surprise but non-defaultable types are the overwhelming majority
of our classes. Easily 9:1. And I'd like to stress *our* classes and not just
wacko-Vladimir's. And, yes, 'convert' is used well beyond ints and the like. The
direction class in 'convert' documentation is a real class and we have plenty of
similar ones not to mention considerably more complex. An enumerator as simple as

enum hamlet_problem { to_be, not_to_be }; 

has no default. I am not sure if extending the above to

enum hamlet_problem { to_be, not_to_be, i_dont_know }; 

will be helpful for poor Hamlet. From the design perspectives adding elements
not relevant to the domain (i_dont_know) is pollution.

I won't be surprised if you find a lot of non-defaultable types if you look
closely around without pre-disposition that any class is supposed to have the
default constructor. One needs to remember that the default constructor was
introduced in C++ (if my memory serves me) so that objects would not be in an
invalid state like 'int i;' can be. If one introduces the default constructor
which does not, in fact, construct a valid object, then it seems to defeat the
purpose. 

V.