Re: [boost] [review] Convert library

Subject: Re: [boost] [review] Convert library
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2014-05-26 03:24:24

On 26/05/2014 02:59, quoth Thijs (M.A.) van den Berg:
> The value of convert to me seems to be more in the context of
> generic programming for a wide range of types with a uniform
> interface than for a simple interface for specific types for
> which there are already simple & standard alternatives.

This comment in the context of strings made me think of stateful 
converters.  I haven't really looked at the proposed library too 
closely, but is it supported/expected to have mutable converters?

An example of this in another conversion library was one that provided 
for conversion from std::wstring to const char *.  This was handled by 
having a local instance of a "context" object (possibly analogous to the 
converter) that internally stored any memory allocated during the course 
of the conversion, such that the returned pointer remained valid as long 
as the context object was in scope, and no memory was leaked.

Furthermore, the way the templates were defined made it a compile error 
to try to perform that type of conversion without supplying a context 
object (whereas converting from std::wstring to std::string could be 
done with or without one, as it did not require intermediate storage).

The same context object could be used in multiple conversions and each 
would be kept distinct (so no conflicts between returned pointers), but 
all freed at the end.