Re: Unnecessary New Closures

[David Manura <dm.lua@...>]

Patrick Donnelly <batrick.donnelly <at> gmail.com> writes:
> Perhaps an inline function addition...I just find
> these constructs inelegant:
> 
> local x = function(a, b) end
> function sort()
>   table.sort(sometable, x)
> end

The following adds only the overhead of a comparison test and provides the
advantage that the object is only constructed if sort is run at least once:

local x; function sort()
  x = x or function(a, b) end
  table.sort(sometable, x)
end

This applies similarly for tables or any other resource:

local is_valid
function test(x)
  is_valid = is_valid or {a=true,b=true,d=true}
  return is_valid[x]
end

Still, there could be advantages if it were allowed for a variable to be
syntactically declared inside a block but lexically scoped in a parent block:

function test()
  return (scope 2: {a=true,b=true,d=true})[x] -- only construct once
end

That's probably something for Metalua.