Re: Iterators vs Lambdas

[Alexey Melnichuk <mimir@...>]

Hello, David.

> What do you guys prefer between iterators vs lambdas? For example, you
> have a function find("/directory", "pattern") where the function will
> find every entries that matches the pattern.

> Would you rather use like that:

> for entry in find("/directory/", "*bar")
>     -- Play with entry
> end

> Or with a lambda called with the entry as argument

> find("/directory/", "*bar",
>     function (entry)
>         -- Play with entry
>     end
> )

> The second one maybe more performant (I guess, not tested) on huge
> objects. Also the second one may use different function as parameter
> without rewriting the for loop in the first one.

> So I would like what you usually prefer before I'm going further in my
> project because it will require a lot of these kind of calls :-).

I had the same question when i work on my ODBC binding.
I like the first because it is easy to read.
But with second you can:
1) properly clean up after iteration
2) return   error   code   (my  library  return  error  object  with
SQLSTATE,  Message  etc.) With lua 5.1 you can not rise error with non
string. Of course you can pass thrue error from callback function.
3)  return  result  after  iteration.  I  stop iteration when callback
function return any values (even nil) and return them as result.

I provide both variant in my libraries, but I prefer second one.

  -- cnn - ODBC connection

  cnn:each(sql,param,function(f1,f2) ... end)
  -- here there no open statement

  for f1, f2 in cnn:each(sql,param) ... end
  -- we need call gc to ensure that statement is close
  -- but if there error while iteration then we can go to
  -- error handling code in outer block and statement
  -- will be open until gc