Re: [ANN] Lua 5.2.0 (work4) now available

[Petite Abeille <petite_abeille@...>]

On Aug 7, 2010, at 12:47 AM, Javier Guerra Giraldez wrote:

> my 2 centavos (S/.):

And I raise you with my 2 centimes :)

> 
> the require() function hasn't changed (AFAIK), so there's no
> difference for users of libraries.  that also means that what a
> library must provide to its users hasn't changed either.   if your
> libraries did advanced package managing, you can still do the same; so
> i don't think it's a 'real' loss of functionality, just (maybe) a loss
> of convenience

True, but now I will need to re-implement it by myself instead of using a standard, well defined module function.

> for 'advanced' packages, you can always replicate what module() did.
> it's not difficult; 

Sure, one can write its own [1], for example:

local debug = require( 'debug' )

local function UpValues( aFunction )
    local anIndex = 0
    
    return function()
        anIndex = anIndex + 1
        local aName, aValue = debug.getupvalue( aFunction, anIndex ) 
        
        if aName then
            return anIndex, aName, aValue
        end
    end
end

local function GetEnvironment( aFunction )
    local aFunction = ( type( aFunction ) == 'function' and aFunction or debug.getinfo( aFunction + 1, 'f' ).func )

    for anIndex, aName, aValue in UpValues( aFunction ) do
        if aName == '_ENV' then
            return aValue
        end
    end
end

local function SetEnvironment( aFunction, anEnvironment )
    local aFunction = ( type( aFunction ) == 'function' and aFunction or debug.getinfo( aFunction + 1, 'f' ).func )
    
    for anIndex, aName, aValue in UpValues( aFunction ) do
        if aName == '_ENV' then
            return debug.upvaluejoin( aFunction, anIndex, function() return anEnvironment end, 1 )
        end
    end
end

local function Module( aName )
    local aModule = package.loaded[ aName ] or { }
    
    aModule[ '_M' ] = aModule
    aModule[ '_NAME' ] = aName
    
    package.loaded[ aName ] = aModule
    
    SetEnvironment( 2, aModule )
end

local print = print
local require = require

Module( 'DWIM' )

function dwim()
    print( 'dwim', _M, _NAME )
end


dwim()

print( GetEnvironment( dwim ) )

print( require( 'DWIM' ).dwim )


Module( 'DWIM2' )

function dwim()
    print( 'dwim', _M, _NAME )
end


dwim()

print( GetEnvironment( dwim ) )

print( require( 'DWIM2' ).dwim )


% lua -v TestModule.lua
Lua 5.2.0 (work4)  Copyright (C) 1994-2010 Lua.org, PUC-Rio
dwim	table: 0x100106d10	DWIM
table: 0x100106d10
function: 0x100106ff0
dwim	table: 0x100107290	DWIM2
table: 0x100107290
function: 0x100107460

But, as Everett mentioned somewhere else in this thread [2], this will lead to chaos as everybody and their dog will, one way or another, re-implement such functionality, in slightly incompatible ways :/ 

Oh, well...

[1] http://lua-users.org/lists/lua-l/2010-06/msg00313.html
[2] http://lua-users.org/lists/lua-l/2010-08/msg00143.html