Re: [boost] a safe integer library

Subject: Re: [boost] a safe integer library
From: Brook Milligan (brook_at_[hidden])
Date: 2016-01-12 21:57:53

On Jan 12, 2016, at 7:30 PM, Robert Ramey <ramey_at_[hidden]> wrote:
> I don't remember what I was thinking when I wrote that.  But it might be that I didn't want users to use the function without checking the return value.

Perhaps that is a more useful statement for the documentation.  It is certainly more informative.

>> This solution suggests that wrapping this particular construct in something that is unambiguously safe would be a good idea:
>> 
>> 	template < typename R, typename T >
>> 	bool is_convertible<R>(T const& t)
>> 	{ return checked_cast<R>(t).no_exception(); }
>> 
>> Does that make sense?
> 
> I'd have to think about it. but it looks OK.
> 
> BTW there is a function in mpl "is_convertible" which implements this behvaior at compiler time - not runtime as here.  So you might want to change the name

Oops.  I forgot the constexpr part.  That makes it work at compile time just fine.

It seems to me that the appropriate place for such a function like this is in your safe numeric library, not elsewhere.  It is closely allied to the semantics of what a safe numeric type means.  Additionally, if nothing else, it serves as an example of the proper use of the checked_result type.

Cheers,
Brook