Re: iterator sequences (was: Standard libraries)

[steve donovan <steve.j.donovan@...>]

On Fri, Jan 1, 2010 at 5:42 PM, Wim Couwenberg <wim.couwenberg@gmail.com> wrote:
> for i, x in seq(ipairs(list)) (map, square) (filter, is_odd) do
>    print(i, x)
> end

That reads well, not noisy at all.

But your map functions do have to follow the (i,val) convention

> local function square(i, x)
>    return i, x^2
> end

Although an adapter can be written for single-valued functions:

function adapt_fun(fun)
  return function(i,x)
    return i,fun(x)
  end
end

and the iterator known in Python as enumerate() can convert
single-valued iterators to the ipairs form.

steve d.

PS Sequence chains like this have a big advantage over repeated
map/filter array operations, in that there are no potentially large
temporary arrays created.  (I tend to prefer single-valued iterator
operation chains)