From: John Torjo (john.lists_at_[hidden])
Date: 2004-03-08 11:10:56
David Abrahams wrote:
>John Torjo <john.lists_at_[hidden]> writes:
>
>
>
>>Aleksey Gurtovoy wrote:
>>
>>
>>
>>>David Abrahams wrote:
>>>
>>>
>>>
>>>
>>>>I just tried using the lambda library for the first time. Here's
>>>>what came out of it, after some struggle:
>>>>
>>>> #include <boost/lambda/lambda.hpp>
>>>> #include <vector>
>>>> #include <numeric>
>>>>
>>>> using namespace boost::lambda;
>>>>
>>>> struct X
>>>> {
>>>> X() : count(1) {}
>>>>
>>>> unsigned long count;
>>>> };
>>>>
>>>> std::vector<X> xs(10);
>>>> unsigned long n = std::accumulate(
>>>> xs.begin(), xs.end(), 0UL,
>>>> _1 + (&_2) ->* &X::count);
>>>>
>>>>
>>>>
>>>>
>>>Views make it much cleaner, both conceptually and syntactically:
>>>
>>> unsigned long n = accumulate( transform_view( xs,
>>>mem_fn(&X::count) )
>>> , 0UL
>>> );
>>>
>>>
>>>
>>>
>>Indeed ;)
>>Using views/ranges makes the code much simpler/clearer.
>>
>>In time, I've accepted the fact that there's not much point in using
>>in-place functions (like _1 + _2, etc.), since in real-life they just
>>complicate the code.
>>So I just create a new function (in anonymous namespace), and that's it.
>>
>>And I use boost::bind, which rocks big time :D
>>
>>
>
>What do you suppose boost::bind does other than creating an in-place
>function? I believe you guys are confusing issues. While I think
>
>
Of course, I knew that ;) I did misexplain however. What I should have
said was that I prefer to create a simple and straightforward function
(usually a one-liner) and use it with boost::bind over using
boost::lambda. Makes the code more self-explanatory.
>views have benefits, the problems I mentioned above were not caused by
>the use of iterators or in-place functions:
>
> std::vector<X> xs(10);
> unsigned long n = std::accumulate(
> xs.begin(), xs.end(), 0UL,
> _1 + bind(&X::count, _2));
>
>Is really no worse than the alternative cited above:
>
> unsigned long n = accumulate(
> transform_view(
> xs, mem_fn(&X::count) )
> , 0UL);
>
>
>
what we were trying to say was that if you use views/ranges, problems
like the one you've shown above usually don't appear/ appear very seldom
(at least to me ;) ).
Best,
John