Re: Map and filter without intermediate tables

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

On Thu, Jun 7, 2012 at 1:06 PM, Geoff Leyland <geoff_leyland@fastmail.fm> wrote:
> Yes, but if you have a function generating a sequence and a series of sequence processors that might do things like map or filter that sequence, then you might consider avoiding intermediate tables, since there was never a table in the first place.

That was the idea behind pl.seq

https://github.com/stevedonovan/Penlight/blob/master/lua/pl/seq.lua

E.g,

> f = stringio.open 'one\n\ntwo\nthree'
> seq(f:lines()):filter('~','^t'):upper():printall()
TWO THREE

But I've never bothered to check the speed - I suppose the thing about
iterators is that they are 'lazy lists', potentially infinite.

> seq(function() return math.random(1,10) end):take(5):printall()
4 9 9 8 2

Personally, I prefer method chaining to functional application, since
my brain tends to work best left-to-right.

steve d.