Re: problem with the execution of an array of functions using cps (continuation passing style)

[Daurnimator <quae@...>]

On 26 January 2015 at 15:38, Pablo Botelho <pablo.bcb@gmail.com> wrote:
> local f1 = function(context, continue)
>   context.foo = 'foo'
>   print 'i am function one'
>   continue()
> end
>
>
> local f2 = function(context, continue)
>   context.bar = 'foo'
>   print 'i am function two'
>   continue()
> end
>
> local f3 = function(context, continue)
>   context.breno = 'magro'
>   print 'i am function three'
>   continue()
> end
>
>
> local f4 = function(context, continue)
>   context.cafil = 'ratos'
>   print 'i am function four'
>   print 'ia am the last function of the array'
> end
>
> local context                = {}
> local current_function_index = 0
> local function_array         = { f1, f2, f3, f4 }
>
> local continue = function()
>   -- fetchs the current function of the 'function_array' variable
>   current_function_index = current_function_index + 1
>
>   print('index:' .. current_function_index)
>
>   local current_function = function_array[current_function_index]
>
>   -- tests to see if theres a next function to execute
>   if type(current_function) == 'nil' then
>     return error('can not call "continue" on last function of the chain')
>   end
>
>   -- executes the next function passing the context and the continuation
>   current_function(context, continue)
> end
>
> continue()
>
>
> -----------
>
> The idea is to trigger the execution of the first function of the
> 'function_array' variable
> and then asynchronously trigger the next function in 'function_array' by
> calling the 'continue' argument
>
> I can see why the error is happening but I cant figure a way to get it to
> work.
>
>
>
>

the `continue` function cannot see itself.
instead of `local continue = function()`
you need: `local continue; continue = function()`
or use the sugar: `local function continue()`