get_set_var.lua

#!/bin/lua

local lib = {}

function lib.pair(init)
  local variable = init
  return function()
    return variable
  end, function(value)
    variable = value
    return true
  end
end

function lib.typed(value)
  return function()
    return value
  end, function(new)
    if type(value) == type(new) then
      value = new
      return true
    else
      return nil, ("Got %s, expected %s"):format(type(new), type(value))
    end
  end
end

function lib.static(init)
  local variable = init
  return function()
    return variable
  end, function()
    return nil, "Static variables cannot be set"
  end
end

function lib.wrap(pair)
  return function(value)
    if value then
      return pair[2](value)
    else
      return pair[1]()
    end
  end
end

return lib