Re: Iterators vs Lambdas
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- Subject: Re: Iterators vs Lambdas
- From: Philipp Janda <siffiejoe@...>
- Date: 2013年9月10日 19:37:05 +0200
Am 10.09.2013 18:27 schröbte David Demelier:
Hi,
Hi!
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.
Guessing doesn't count.
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 prefer the first variant (iterators), but you can easily provide both:
Implement the iterator version and use something like this
do
local function cb_helper( func, iter, st, ... )
local var_1 = ...
if var_1 ~= nil then
func( ... )
return cb_helper( func, iter, st, iter( st, var_1 ) )
end
end
function make_cb_func( gen )
return function( func, ... )
local iter, st, var = gen( ... )
return cb_helper( func, iter, st, iter( st, var ) )
end
end
end
to implement the callback version.
Example:
local foreach = make_cb_func( pairs )
foreach( print, { 1, 2, 3, 4 } )
==>
1 1
2 2
3 3
4 4
Drawback of the implementation above is that the callback function
always comes first. You could use a temporary table or the vararg[1]
library to handle callback functions at the end of the vararg parameter
list (or implement make_cb_func() in C!) ...
[1]: http://luarocks.org/repositories/rocks/#vararg
Warm regards,
Philipp