About me:
I've been learning Elixir intensively for a few months and hope to get a
job as an Elixir/Phoenix developer soon.
I don't have too much experience developing languages myself, I just
made a YAML
templating language
<https://taonexus.com/publicfiles/playground/yaml-var/yaml-var-converter>
so take what I have to say with a grain of salt!
This is my personal experience with Elixir, if there are any mistakes or I
am misusing the language let me know!
As a user of Elixir, it seems to me that I can *write ternary expressions
in Elixir by treating the if statement as an expression* and it remains
highly readable.
Other languages don't do this and it is a "quirk" of Elixir. In Python, C,
and C++, a regular if statement itself does not become a value and can't be
used as an rvalue; it would be a syntax error to assign the if statement
itself. Only Elixir allows this, and as a result if can be used as a
ternary expression!
The "Ternary" Expressions in C/C++, Python, Elixir
Here's my evidence:
This is a ternary construct:
avariable = true ? 42 : 43
avariable is set to 42 if true is true. If you can set avariable to one of
two values based on a boolean test, using an expression, then that is a
ternary expression. Here's a language that has a ternary expression:
JavaScript.
avariable = true ? 42 : 43 //javascript
[image: image.png]
as you can see, it gets set to 42.
Now let's try it in Python. Well, the straightforward way doesn't work:
# Python:
[image: image.png]
Instead Python does it this way:
avariable = 42 if True else 43
#Python:
[image: image.png]
This is special syntax that differs from a normal if expression, it was
specifically introduced to be Python's equivalent of the ternary operator. As
I recall, Python picked this since frequently one of the values is more
common. *(As an aside, in the history of language development, Perl also
has an if that can come after an expression as a "statement modifiier", but
in Perl that version didn't have an else clause; Perl instead used the
ternary expression with ? for this purpose.)*
Instead of "a? b : c" it just reads "b if a else c" in Python.
Here's Elixir's version:
iex(1)> avariable = if true do 42 else 43 end
42
[image: image.png]
if we set it to false instead we would get 43.
[image: image.png]
It's still just like a ternary operator. Instead of "a ? b : c" it just
reads "if a do b else c end".
Naturally the short form also works:
[image: image.png]
If you tried to do this in C++ or Python you would get an error. (You can't
assign = if () ... in those languages.)
# Can't do it in the Elixir order in Python. In Python this would be an
error:
# Python:
[image: image.png]
Because as mentioned earlier, *if *statements can't be treated like an
expression the way the whole if can be treated as an expression in Elixir.
For comparison, you can't do that in C++ either. This is broken code in
C++:
// C++
#include <iostream>
int main() {
int value = if (true) 42 else 43; // This line will cause a compilation
error in C++
std::cout << "Value is: " << value << std::endl;
return 0;
}
[image: image.png]
Instead it works like this:
#include <iostream>
int main() {
int value = true ? 42 : 43; // value is 43
std::cout << "Value is: " << value << std::endl;
return 0;
}
[image: image.png]
>From this comparison, Elixir is the only language among these three
languages that uses if exactly in this way. Using if the same way in any
of the other languages would be a syntax error, since the if expresssion in
the other languages doesn't itself have a value and can't be used as an
rvalue.
In summary then, we have this language comparison guide:
[image: image.png]
I think it works perfectly well for this purpose. Let me know if I've
misunderstood the syntax or I'm abusing the language by doing it this way!
On Fri, Jan 26, 2024 at 11:07 PM Brandon Gillespie <bran...@cold.org> wrote:
> I'm sure there's a reason, so I figured I'd ask why there isn't a ternary
> expression?
>
> It seems like ternary would help with the functional paradigm of Elixir.
>
> I realize one can use the `if...` as a construct, but it just isn't very
> readable (imho of course).
>
> Consider:
>
> some_function(
> log_id,
> if(type == :before, do: action.order, else: action.order + 1)
> )
>
> vs:
>
> some_function(log_id, type == :before ? action.order : action.order + 1)
>
> Invariably when I come upon a use case for a single-line if, I end up
> never liking its readability. So instead of the above, I end up with:
>
> new_order = if type == :before, do: action.order, else: action.order + 1
> some_function(log_id, new_order)
>
> While this works, it's also not great, because I try to avoid assignments
> wherever possible (being a functional language and all).
>
> Anyway, just a question more than anything. Thanks!
>
> -Brandon
>
>
> A few other things to address suggestions I know may come:
>
> 1. "It's too cryptic" — I just need to point to the `&(&1)` type shortcut
> to show precedence for smaller syntax sugar in elixir.
>
> 2. Just make a `ternary()` function — but I don't think it really helps
> any with the visual readability, and in fact is probably LESS so since it's
> a less known function/name in the general programming world, where ternary
> ?: is pretty ubiquitous.
>
> 3. use pipes in the above last example — not what I want, because that
> requires re-ordering the function's arguments. That's a bizarre requirement
> just because we can't handle ternary's.
>
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