Elixir Curiosities

  • Ever been curious about why something is the way it is in Elixir?
  • Or perhaps the way something works the way it does?
  • If so then this thread is just for you :003:

Perhaps you’ve had similar queries in the past which have since been answered, if so please add them to this thread to help others who might be wondering the same :101:

This thread is also a great way to test your own understanding - if you think you know an answer to a query please share it :023: (and if you think you can improve on an answer someone else has provided, please do).

We may also use the thread to propose changes or additions to the official Elixir FAQ, so please help us by taking part. :slight_smile:


One of the first things I was curious about was why we had to do this in Elixir:

name = "elixir"

and couldn’t just do this:

name = "elixir"

The answer was provided by PragDave in his book Programming Elixir; that the syntax is a reminder that we are working with immutable data and that functions don’t modify data, they return completely new versions of it.


Actually you can. Google “tuple modules”. But that code smells :048:


/me is saddened by the demise of tuple modules in recent erlang’s, great for passing around data and functions that was not just anonymous functions. ^.^


There’s a discussion about it here that you might find interesting: https://github.com/elixir-lang/elixir/issues/3254


Ok here’s another curiosity…

Why do we use \\ for default parameters and not just =

I’m guessing because this is how it is in Erlang and perhaps because of the wiring of the match operator, but still, am curious! :101:


Nope! ^.^

I’d imagine it is these:

  • Erlang does not have a concept of optional arguments, so nothing to pull from there.
  • = is already used in matchspec’s for function definitions, so cannot use it or it would be ambiguous (def blah(i = 1) would mean is default arg of 1 or only ‘matches’ on a 1, ambiguous).
  • Ruby has no such construct that I’ve ever seen as \\ either, so my guess is that it is just an unused operator so it was taken for this purpose, especially as it does not require hitting the Shift key to access.

I’m curious about its history as well. :slight_smile:


I think it’s inspired on Perl’s default argument operator: https://perlmaven.com/how-to-set-default-values-in-perl


That’s interesting - I didn’t know Erlang doesn’t allow default arguments in functions. That makes me more curious why it’s not the = (as per Ruby) but \\ (as it is in Perl) :101:


Well, I guess the fact that = is used for matching is the reason it’s not used for default parameters, it would. But why \\, I’m just as curious as you are! Maybe it’s inspered from Perl like @vidalraphael said, thank you for that, I didn’t know!

But I catch me doing a lot of this:

def add(a), do: add(a, 1)
def add(a, b), do: a + b

Instead of:

def add(a, b \\ 1), do: a + b

The \\ operator was very confusing to me in the start (I keep doing // instead of \\). I guess that’s why I go with the first option so many times.


Ahh! I forgot about Perl! That makes it click more for me now. :slight_smile:

I’d probably have made it := or so myself, even if it involves hitting Shift. :slight_smile:


Same here :joy:

Whenever I use a default arg I keep waiting for the compile error. I think it’s because // means comment in a lot of languages, so \\ just feels wrong at the beginning (unless you have a background in Perl :smiley:).


PS.: in Perl they use // and not \\, so it’s just a vague inspiration. So the question why \\ still pertinent I guess, it’s just more specific maybe:

  • Why \\ instead of // if it was inspired in Perl? And if not, why \\ at all?

:= - Pascal style!!!


Exactly! ^.^