Re: [boost] [Boost.Local] Review

Subject: Re: [boost] [Boost.Local] Review
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2011-11-23 07:04:17

On Wed, Nov 23, 2011 at 6:54 AM, Joel de Guzman
<joel_at_[hidden]> wrote:
> On 11/23/2011 7:06 PM, Lorenzo Caminiti wrote:
>>> just using phoenix and/or lambda :
>>> >
>>> > int max = 0;
>>> > auto small = _1 < max; // (2)
>> Or even better:
>>
>> int max = 0;
>> auto small = [max](int x) { return x < max; } // (3)
>>
>> IMO (and others have second this point), (3) is better than (2)
>> because at some point (3+ years from now?) everyone will be
>> comfortable with C++11 lambda syntax (3) because it's part of the
>> standard while there will still be people on your team that will have
>> no idea what you meant in writing (2). By the same token, the syntax
>> of (1) (statement syntax for the body) can be considered better than
>> the one of (2) even if (1) is more verbose and than (2) (verbosity
>> which might be a plus in the context to make the syntax more clear--
>> in fact (3) is more verbose than (2) but it is the new standard). All
>> of that said, if the a syntax is more or less understandable is a
>> subjective matter so I recognize that you and/or Hartmut feel
>> differently on this topic.
>
> No it's not better. First: (3) is not polymorphic! (2) can be reused
> regardless of the type of _1. To make it clear:
>
>   auto less = _1 < _2;
>
> The above can be reused in any expression as long as they
> have the less-than relation. E.g. less(i, 123), less(str, "hello),
> etc. It's these simple 1-2-3 liners where Phx/Lambda shine.
> You'd have to be absurdly dumb to get those expressions wrong!
>
> Second: (2) is more succinct.

For some of our users/problems polymorphism might not be relevant
while using statement syntax for the body might. For those
users/problems (3) might be worst than (2) because is does not use
statement syntax in its body (worst error messages + less readable by
others). We leave that decision up to our library users and we are all
content.

--Lorenzo