Re: [ANN] lua-Coat 0.5.0 : Yet Another Lua Object-Oriented Model

[François Perrad <francois.perrad@...>]

2009/8/26 David Manura <dm.lua@math2.org>:
> On Mon, Aug 24, 2009 at 1:14 PM, François Perrad wrote:
>> lua-Coat is a Lua 5.1 port of Coat (http://www.sukria.net/perl/coat/), ...
>> Comment, bug report, patch are welcome.
>
> So if Moose is the ultimate class library for Perl, and Coat is a
> quasi-subset Moose, and lua-Coat is a port of Coat to Lua, then does
> that imply that lua-Coat is a quasi-subset of the ultimate class
> library for Lua?
>
> We can try it on the benchmark [3]
>
>  -- added code
>  function makeob5()
>    require "Coat"
>    class "ob5"
>    has.data = {is='number',default=0}
>    function method:test() self:data(self:data() + 1) end
>    return _M()
>  end
>  addbenchmark("Object using lua-Coat", "ob:test()", makeob5())
>
> Results:
>
>  $ lua bench.lua            # using count = 10000000
>  2.969   Standard (solid)
>  3.406   Standard (metatable)
>  3.64    Object using closures (PiL 16.4)
>  2.25    Object using closures (noself)
>  16.735  Object using lua-Coat
>  1.469   Direct Access
>  0.484   Local Variable
>

A benchmark makes sense only if it's representative of your usage.

>> basic_type = type
>> local basic_type = basic_type
>> local function object_type (obj)
>>     local t = basic_type(obj)
>>     if t == 'table' then
>>         pcall(function () t = obj._CLASS or t end)
>>     end
>>     return t
>> end
>> _G.type = object_type
>
> The above code implies that type {_CLASS='x'} == 'x', which is
> inconsistent with the Lua specification [1].  This might not seem
> important, but consider the case of some code that operates on a table
> whose key names are generated from user input.  The above would
> introduce subtle edge cases (or security holes).  The above also
> implies that type(t) will now have the overhead of a pcall when t is a
> table.  I recommend against redefining type().
>
>> function before (class, name, func) .....
>>     class[name] = function (...)
>>         local result = func(...)
>>         super(...)
>>         return result
>>     end
>
> To handle multiple return values, you can use the CPS style [2].
> However, I question whether before and after modifiers should alter
> return values.  It appears Coat (in $modified_method_code) only does
> so for around modifiers.
>
> [1] http://www.lua.org/manual/5.1/manual.html#pdf-type
> [2] http://lua-users.org/wiki/VarargTheSecondClassCitizen
> [3] http://lua-users.org/wiki/ObjectBenchmarkTests
>
>