Re: [boost] Assign V2 - first impression

Subject: Re: [boost] Assign V2 - first impression
From: Christian Holmquist (c.holmquist_at_[hidden])
Date: 2011-06-24 01:28:02

>
>
>>
> Indeed, it's readable. But I talked about 100 unit tests that vary a bit.
> Let's settle for 5. The STL way:
>
> array<int, 1> log_constants = { a1 };
> vector<int> cont;
> int n = n1;
> foreach(i, log_constants)
>  int x = f1(i);
>
>  for(int  j = 0; j < n;++j)
>  {
>    cont.push_front(x);
>  }
> }
> array<int, 2> log_constants = { a2, b2 };
> vector<int> cont;
> int n = n2;
> foreach(i, log_constants)
>  int x = f2(i);
>
>  for(int  j = 0; j < n;++j)
>  {
>    cont.push_front(x);
>  }
> }
> array<int, 3> log_constants = { a3, b3, c3 };
> vector<int> cont;
> int n = n3;
> foreach(i, log_constants)
>  int x = f3(i);
>
>  for(int  j = 0; j < n;++j)
>  {
>    cont.push_front(x);
>  }
> }
> array<int, 4> log_constants = { a4, b4, c4, d4 };
> vector<int> cont;
> int n = n4;
> foreach(i, log_constants)
>  int x = f4(i);
>
>  for(int  j = 0; j < n;++j)
>  {
>    cont.push_front(x);
>  }
> }
> array<int, 5> log_constants = { a5, b5, c5, d5, e5 };
> vector<int> cont;
> int n = n5;
> foreach(i, log_constants)
>  int x = f5(i);
>
>  for(int  j = 0; j < n;++j)
>  {
>    cont.push_front(x);
>  }
> }
>
> Assign v2 way:
>
> csv( // 1
>    deque<int, push_front_>( _nil ) % ( _data = f1 ) % ( _repeat = n1 ),
>    a1
> );
> csv( // 2
>    deque<int, push_front_>( _nil ) % ( _data = f2 ) % ( _repeat = n2 ),
>    a2, b2
> );
> csv( // 3
>    deque<int, push_front_>( _nil ) % ( _data = f3 ) % ( _repeat = n3 ),
>    a3, b3, c3
> );
> csv( // 4
>    deque<int, push_front_>( _nil ) % ( _data = f4 ) % ( _repeat = n4 ),
>    a4, b4, c4, d4
> );
> csv( // 5
>    deque<int, push_front_>( _nil ) % ( _data = f5 ) % ( _repeat = n5 ),
>    a5, b5, c5, d5, e5
> );
>
>
> Isn't this more clear, and less error prone? It is not that much, and not
> "crucial", but the claim of the library is just as modest:
>
>
Quick answer, I'll try to me give more feedback tomorrow:
I don't work a lot with copy'n'paste.  There's always a structure to be find
somewhere, and this structure can be identified and formalized into a
shorter program.
Anyway, my main problem is that I cannot understand your code.
If you were using standard facilities, like std::generate/transform/copy, I
wouldn't need to start from scratch. I would need to study your
documentation quite a lot to figure out what values your code generates.

Thinking out loud, this would be easier to me (made up example):
vector<int> v;
std::generate_n(std::back_inserter(v), 10,
assign::v2::fancy_generator(......));
or
std::copy_n(assign::v2::fancy_iterator(...), 10, std::back_inseter(v));

It seems like your library can build complex generators/converters of some
kind, but it's integration with the containers appears ad-hoc. The above
would allow me to only focus on how to configure the generators, and use my
old-time knowledge on how to use these with std::containers.

- Christian