Re: blocks in Lua (was Re: [PROPOSAL] [PATCH] simple method call)

[Coda Highland <chighland@...>]

On Tue, Jun 16, 2015 at 8:37 AM, Rodrigo Azevedo <rodrigoams@gmail.com> wrote:
>
>> >> > command = input:urldecode():lower():trim():split(' ')
>> >
>> >
>> > You can do this:
>> > command = filter.urldecode.lower.trim.split(' ')(input)
>> >
>> > One of the nice things about this is that the filter chain can be cached
>> > easily:
>> >
>> > f = filter.urldecode.lower.trim.split(' ')
>> > command = f(input)
>> > command2 = f(input2)
>
>
> I'm sorry, I would want to know if the patch I've proposed (the one in the
> subject) can also solve this problem:
>
> f = function(str) -- do something with str
>         return str:upper:lower .. "one"
> end
>
> str = "Testing This "
> str = f(str)
>
> f2 = function(str) -- example given
>        return str:urldecode:lower:trim:split(' ')
> end
>
> command2 = f2(input2)
>
> that also solves the problem?
>
> because with this you can easily understand that ":" are function calls, and
> not confuse with "." syntactic sugar.
>

It should be noted that these chained filters are NOT function calls!
They are not in fact operating on the value of their parameter.
They're not invoked until you pass a parameter to the end result of
the chain.

Every filter is an object that possesses properties that are the
result of certain transformations being performed upon the filter
itself. These could be precomputed at time of construction except for
the recursion, so they're constructed lazily, but they're not function
calls in any practical high-level sense.

It should also be noted that Boris Nagaev's implementation that
requires the use of : for split can actually be fixed to not need it
with a little bit of cleverness. (Specifically, it just needs to
return a closure with the current filter as an upvalue, so the current
filter doesn't have to be passed in as a parameter.)

/s/ Adam