Re: [boost] [endian] Comments on Endian 0.5

From: David Bergman (davidb_at_[hidden])
Date: 2006-07-21 17:14:59

> On Jul 20, 2006, at 4:17 PM, loufoque wrote:

[snip]

> What's ugly?  The ::init()?  It's not *that* ugly.  And it 
> makes the library more useful.  What's the use case for 
> requiring elegant initializers?  I don't see many people 
> doing something like:
> 
>    big4_t x = 42;

What about the use of endian objects where one would expect raw integral
objects? Such use includes

        template<typename DestT, typename SourceT>
        DestT make_double(SourceT val) { return 2 * val; }

        big4_t doubleVal = make_double<big4_t>(21);

The generic code need not even deal with arithmetic at all, such as in

        vector<int> int_vect;
        ...
        vector<big4_t> big4_vect(int_vect.begin(), int_vect.end());

Since we do not have the luxury of two user-defined conversions in the chain
from 'int' to 'endian<...>', which would allow us to write an intermediate
type with both an 'int' constructor and an 'endian' operator, we have to
choose: unions (and other pure POD scenarios) or conversion from raw
integral objects. I think a wise decision was made in the choosing the
latter.

> What good is a single big-endian variable on the stack?  I 
> see far more use cases for these classes in structs and 
> unions, and then writing them out a file descriptor.

But we also want it to be interchangeable - as far as possible - with
integers in generic code (whether templates or "copy-and-pasting".)

/David