Re: Microlight

[Philipp Janda <siffiejoe@...>]

Hi!

Am 18.12.2012 13:29, schrieb Peter Aronoff:
> On Tue Dec 18 2012 @ 12:42, Dirk Laurie wrote:
> > I've analyzed to myself why I felt much more enthusiastic
> > about Microlight in February than I do now.  It's simple: I've
> > been off Python for ten months longer.  I don't  feel a need
> > for e.g. `class`, `callable`, `map` and `filter` any more. I find it
> > more readable to write the equivalent in plain Lua.  The jury
> > is still out on `range`.
>
> I'm curious about the end: "I find it more readable to write the equivalent
> in plain Lua." I've been using Lua more and more lately (instead of Ruby or
> Bash or previously Perl), and I already have my own general-purpose utility
> module that includes `map`, `filter`, `partition`, etc. I understand the
> idea that they are simple to write in plain Lua, but why would you ever
> want to write them *twice* in plain Lua? (Just curious, not trolling.)

Everything IMHO, of course:
map and filter are good examples. Every possible map- or filter-function 
(I can imagine) is not as flexible (and not as clear) as using Lua's 
built-in language features. For example, does your map function take an 
array (w/o holes?), a general table, or an iterator as input? Does it 
return an array, a general table, an iterator, or nothing at all 
(typically called each instead of map)? What if I need one of the other 
possibilities? Does the modification function only influence the values 
or the keys too (or in case of the iterator version: How many values can 
be modified by the function)? Named modification or predicate functions 
are not as general as you would like, because they might have to handle 
that extra useless parameter passed by map/filter. And you can't break 
(you could throw and catch an error for that, though).
Then there are performance reasons: You always need a modification 
function -- possibly a closure -- for map, even if the modification is 
trivial. If you combine map and filter, you will get temporary tables 
(or closures in the iterator case).
And last but not least you add a dependency to your utility module to 
your code although it would be trivial to avoid it.
And everything because you want to write:

    map( filter( t, is_odd ), function( _, v ) print( v ) end )

instead of:

    for i,v in ipairs( t ) do
      if is_odd( i ) then
        print( v )
      end
    end

(And of course I could write it on one line, but try to wrap/indent the 
line above in a meaningful way ...)

Can't say anything about partition, though, since I don't know what it's 
supposed to do.

> P

Philipp