Three stupid questions

[Dmitrii Dimandt]

Hi all

I have three potentially stupid questions totally unrelated to each other.

1. Macro names

I did ask this question a while back: https://groups.google.com/forum/#!searchin/elixir-lang-talk/defmacro/elixir-lang-talk/oKoLVm2nTQ4/drk-Bsus7zQJ

So, the questions still stand: what can we set as macro names, and how to define operators? :)

2. Syntax inconsistency

I realize that "I should've read the docs and the source and understood metaprogramming better", but still...

I've learned to live with the fact that

    f(a, b), do: function_body

but

    f(a, b) do

      function_body

    end

(no comma, no colon in the second case) What I still don't understand is why, for instance, some stuff breaks the convention:

quote do: one_liner

quote do

  multiple_lines

end

to show it together:

    defmacro zz(a), do: quote do: unquote a

This makes me consistently keep track of commas, colons and keep in mind what I'm dealing with: one-liners? multi-liners? macros? any combination of those?

3. Filename extension inconsistency

All files are *.ex, and mix compile will only compile *.ex

mix test requires files to have a .exs extension, and won't even look at *.ex

Why? This caused me a couple of grey hairs when I couldn't understand why mix test wouldn't pick up my newly written tests. mix test path/to/file works perfectly though.

Please, don't kill me :)

[Jason M Barnes]

I don’t know the answer to the first one, but I’ll try to answer the other two inline:

On Tue, Aug 18, 2015 at 2:48 PM, Dmitrii Dimandt <dmi...@dmitriid.com> wrote:

2. Syntax inconsistency

The “do:” part is part of a Keyword list so the comma separates the arguments from the beginning of the Keyword list.

def f(a, b), do: stuff

The comma and colon can be removed due to syntactic sugar:

def f(a, b) do

  stuff

end

“do” is just a special keyword that allows this.  “else” is the same:

if (foo), do: bar, else: baz

if (foo) do

  bar

else

  baz

end

Notice in this example, you can see both keywords used in the Keyword list.

In the case of “quote” notice that there are no arguments, so the Keyword list is the first item:

quote do: stuff

No need for a comma.  But the syntactic sugar still applies — removing the colon:

quote do

  stuff

end

 

3. Filename extension inconsistency

It is just a convention that mix follows.  *.ex is for files that are intended to be compiled.  *.exs is for files that are intended to be run without being compiled.

Jason 

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[Dmitrii Dimandt]

The “do:” part is part of a Keyword list so the comma separates the arguments from the beginning of the Keyword list.

def f(a, b), do: stuff

Aha. Now it makes sense :)

 

3. Filename extension inconsistency

It is just a convention that mix follows.  *.ex is for files that are intended to be compiled.  *.exs is for files that are intended to be run without being compiled.

Aha, now it also makes sense. Kinda :)

Thank you! 

[Onorio Catenacci]

I had an old friend--an older developer.  He was fond of calling things "Conscious Design Decisions"--that is, when a developer could take one path or another (e. g. pick up all .ex* files or just pick up .exs files) and the developer took a path that seemed somehow inappropriate to later developers he'd say "CDD".  

I mean to say that it's true that upon reflection one might decide that we'd rather have it pick up all files in the test directory regardless of extension.  But when it was being built someone had to decide that issue and he decided to pick that convention.  

I feel confident that if we changed mix to pick up both .ex and .exs in the test directory, someone would come along and say "why does the directory have to be called 'test'"?  :)

--

Onorio

[eksperimental]

I don't know the real reason behind it, but to me its a feature that
allows us to run the test really quick without the need to wait for the
compilation.
Test are mean to run only once, just when you need to see if you code
passes all the test and that's it.

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[Dmitrii Dimandt]

I feel confident that if we changed mix to pick up both .ex and .exs in the test directory, someone would come along and say "why does the directory have to be called 'test'"?  :)

Sorry, but that is so wrong. 

[Dmitrii Dimandt]

On Wed, Aug 19, 2015 at 8:54 AM eksperimental <eksper...@autistici.org> wrote:

I don't know the real reason behind it, but to me its a feature that
allows us to run the test really quick without the need to wait for the
compilation.
Test are mean to run only once, just when you need to see if you code
passes all the test and that's it.

Then it's enough for mix to skip the test directory in the `mix compile` target . It would make much more sense than "hey, here we have Elixir code. It looks exactly the same as this other Elixir code, but it has to have a different file extension for some reason" ;)

[Chris McGrath]

.exs files are compiled, just in memory and no beam file is output. So I see .ex files as containing code that needs to ship with your application for it to work, and .exs files as containing code that doesn’t.

.exs files are also handy when you’re trying something out and don’t want to have to clean up a load of beam files afterwards.

Chris

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