[boost] [Conversion] Practical applications

Subject: [boost] [Conversion] Practical applications
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-08-21 12:18:21

Dear Vicente & others,

Would anyone like to share any practical or motivating applications for 
the proposed Boost.Conversion library?

It seems to me that there are practical applications for particular 
types of conversion, e.g. T-to-string and string-to-T, and numeric 
casts, and serialisation.  Apart from that, I am having trouble seeing 
practical reasons for generic conversion.  A motivating case would be 
if a generic algorithm required conversion, but in the cases that I can 
think of either (a) the generic algorithm takes a functor, so the 
caller can pass the currently-required conversion as part of a lambda 
expression, or (b) you might need to select one of several possible 
conversions between a pair of types, which this library can't do, or 
(c) the algorithms are std:: ones which won't work with this library anyway.

Example:

struct person {
   string firstname;
   string surname;
};

vector<person> people;  // sorted by firstname

// Try to find everyone with firstname "John":
std::equal_range(people.begin(),people.end(),"John");

That doesn't work.  Making it work has always struck me as more 
difficult than it should be.  Can this library make it easier?  If not, 
what similar problems can it help with?

Regards,  Phil.