Re: New EEP draft: Pinning operator ^ in patterns

And exactly the opposite in the following case.

#!/usr/local/bin/escript
%% -*- erlang -*-

-define(SOME_MACRO(Y), X = Y + 1).

main(_Args) ->
    X = 14,
    ?SOME_MACRO(X).

On Thu, Jan 28, 2021 at 4:37 AM Leonard B <[email protected]>
wrote:

>
>
> On Wed, Jan 27, 2021, 16:48 Michael P. <[email protected]> wrote:
>
>> On Thu, 14 Jan 2021 13:13:54 -0500
>> Leonard B <[email protected]> wrote:
>>
>> > IE, if a variable is previously assigned within the outer scope use
>> > that variable within the inner scope.
>> > This, in my addled mind, makes more sense
>> >
>> > EG:
>> > %% X is from outer scope, L is from outer scope, V is local to
>> comprehension
>> > X = 5.
>> > L = [1,2,3,4,5].
>> > [V || {X, V} <- L].
>>
>> Done?
>>
>
> This was a broken example. Excuse formatting, on mobile. Should have been.
>
> > EG:
> > %% X is from outer scope, L is from outer scope, V is local to
> comprehension
> > X = 5.
> > L = [{1, a}, {2,b}, {3,c}, {4,d}, {5,e}].
> > [e] =:= [V || {X,V} <- L].
>
> What I was getting at is that for many newcomers the scoping of X is a
> surprise. I'm totally fine with this, and that possibly injecting variables
> from outer to inner scopes would be more 'logical'.
>
> Changing how scoping worked would probably be a huge change and have worse
> issues. It's just that in my mind I look at the eep and I personally see it
> boiling down to scoping.
>
> ```
>> Eshell V10.2.4  (abort with ^G)
>> 1> X = 5.
>> 5
>> 2> L = [1,2,3,4,5].
>> [1,2,3,4,5]
>> 3> [V || {X, V} <- L].
>> []
>> 4> [{X, V} || V <- L, V /= X].
>> [{5,1},{5,2},{5,3},{5,4}]
>>
>> 5> Lt = [{1, 2}, {2, 3}, {4, 5}, {5, 6}, {6, 7}, {5, 8}].
>> [{1,2},{2,3},{4,5},{5,6},{6,7},{5,8}]
>> 6> [V || {X, V} <- Lt].
>> [2,3,5,6,7,8]
>> 7> [V || {Selector, V} <- Lt, Selector == X].
>> [6,8]
>> ```
>> Names should be swapped (X, Selector).
>>
>> Naming is a burden; but also an opportunity.
>>
>> ~M
>>
>> --
>>
>> Corporation-independent Public Broadcasting is the best innovation
>> since someone said, that the volcano will erupt anyway or not, no
>> matter how many virgins are thrown into it or not.
>>
>> Unternehmensunabhängiger Öffentlich-rechtlicher Rundfunk ist
>> die beste Innovation, seit jemand sagte, dass der Vulkan eh
>> ausbricht oder nicht, egal wieviele Jungfrauen man da reinwirft
>> oder nicht.
>>
>>
>>
>>
>>