Re: A die(reason) or exit function is missing, isn't it?

[Rici Lake <lua@...>]

On 25-Jan-07, at 5:21 PM, Jan Schütze wrote:

> Correct.
> But only for error and exception handling.
>
> I don't need it to handle an failure or an exception, its normal case 
> - so there should be a normal function to do this, without such a big 
> (and good working!) workaround, which Romulo posted.

Surely if you call a function "die", you're implying that it's a 
response to a failure or exceptional condition :) In which case, using 
an error() based exception system seems entirely appropriate.

If you want to do a "compressed return" from a nested recursion, you 
should think seriously about coroutines, which make that convenient, as 
well as being more flexible because they give the option of accepting a 
result or continuing a search.

For example:

trythis = coroutine.yield

function find()
  for value in some_query(database) do
    find2(database, value)
  end
end

function find2(database, value)
  for value2 in some_other_query(database, value) do
    find3(database, value, value2)
  end
end

function find3(database, v1, v2)
  for result in yet_another_query(database, v1, v2) do
    trythis(result)
  end
end

-- main search

local function search()
  local finder = coroutine.wrap(find)
  local result
  repeat
    result = finder()
    if checks_out(result) then return result end
    until not result
  end
  error "Not found"
end




> Just posted mainly to help improving lua with what is often needed in 
> developing web. applications. But you are correct, depends on the 
> point of view, and where(/how often)  you need such functionality.