Re: string.gsub accepting a callable userdata

[Jerome Vuarand <jerome.vuarand@...>]

2012/12/13 steve donovan <steve.j.donovan@gmail.com>:
> That does work - gsub respects __index, which is nice (I had to check this)
>
> Best global solution in such a situation is the following monkey patch:
>
> local gsub,type = string.gsub,type
>
> function string.gsub(s,pat,repl)
>    if type(repl) == 'userdata' then
>       local obj = repl
>       repl = function(...) return obj(...) end
>    end
>    return gsub(s,pat,repl)
> end

To avoid the creation of a closure on each call, you can cache one:

local gsub,type = string.gsub,type
local ref = setmetatable({}, {__weak='v'})
local function unref(...) return ref[1](...) end

function string.gsub(s,pat,repl)
   if type(repl) == 'userdata' then
      ref[1] = repl
      repl = unref
   end
   return gsub(s,pat,repl)
end