Re: [proposal] infix function syntax sugar

[Philipp Janda <siffiejoe@...>]

On 18.12.2011 10:09, Dimiter "malkia" Stanev wrote:
> -- Here is a very poor attempt :)
> 
> local function infix(...)
>     local args = {...}
>     local nargs = #args
>     local r = args[1]
>     for k=2,nargs,2 do
>        r = args[k](r, args[k+1])
>     end
>     return r
> end

This is a very nice idea, one of those gems one sometimes finds on this
mailing list. I would write it differently, though, to avoid unnecessary
garbage as requested by the OP (although I still can't see how infix
functions would help him solve his userdata allocation problem):

local function infix( o1, ... )
  -- if type( o1 ) == "table" then o1 = infix( unpack( o1 ) ) end
  for i = 1, select( '#', ... ), 2 do
    local f, o2 = select( i, ... )
    -- if type( o2 ) == "table" then o2 = infix( unpack( o2 ) ) end
    o1 = f( o1, o2 )
  end
  return o1
end


> 
> local function add(a,b)
>     return a + b
> end
> 
> print( infix( 12 ,add, 3 ,add, 10 ) )
> 
> 

Philipp


> 
> On 12/17/11 9:23 PM, Xavier Wang wrote:
>> hi robero and list,
>>
>> i'm inspired by the post about implement c enum. somebody said the
>> getflags function shoud return a userdata to implement a contains
>> function. i think its a good idea, excerpt a details: thus will allocate
>> memory.
>>
>> i'm run lua on a embedded system， embedded systemembedded system, nokia
>> n73 cellphone. my game will lag if i allocate memory in draw function
>> since the garbage collection. so we avoid any memory in event loop. but
>> i really miss the contains function, so i think a syntax allow use
>> function as infix operator will be great.
>>
>> e.g. if i have a function add(a, b), i can call it with a ｀add｀ b, its
>> a syntax sugar of add(a,b)
>>
>> its very simple and can used in many situations, e.g. bitop calls, and
>> flags contains test.
>>
>> has anybody agree me? i hope this feature can appear on lua5.3 :)
>>
>> thanks everybody~
>>
>