feat(transient-vector): adds initial support for transient vector

[Samy-33]

No description provided.

[Samy-33]

I noticed that we don't have a call in persistent_vector. Any reason for that?

In clojure

([1 2 3] 5)

throws and IndexOutOfBoundException, we should have the same behaviour or we can prefer nil punning here? Any reason why clojure can't just return nil instead of throwing exception?
I prefer nil punning personally, but is it valuable enough to divert from clojure's behaviour?

Also, vector is not a 2-arity fn in clojure, but we have declared it in jank. It makes sense to me to have it, but again diverting from clojure's behaviour.

Let me know your thoughts on this, @jeaye

[jeaye]

I noticed that we don't have a call in persistent_vector. Any reason for that?

In clojure

([1 2 3] 5)

throws and IndexOutOfBoundException, we should have the same behaviour or we can prefer nil punning here? Any reason why clojure can't just return nil instead of throwing exception? I prefer nil punning personally, but is it valuable enough to divert from clojure's behaviour?

Also, vector is not a 2-arity fn in clojure, but we have declared it in jank. It makes sense to me to have it, but again diverting from clojure's behaviour.

Let me know your thoughts on this, @jeaye

Yeah, we just haven't implemented that behavior on persistent_vector yet. However, the way that it's done is a little tricky, since we actually are hard-coding this right now, in dynamic_call. It's a huge performance win to do this, compared to implementing callable for those types, since that will result in vtable ptrs and virtual dispatch. If you'd like to add support for persistent_vector in there, take a look at callable.cpp:70, as well as evaluate.cpp:260.

As a rule, if Clojure throws, jank throws. We're in the business of hitting parity, not changing semantics (even when we don't necessarily like those semantics).

[jeaye]

Some comments for things to improve, but overall this is great! Be sure to test it all in ./build/jank repl, since we don't yet have a test suite for these things.

[Samy-33]

Tests:

➜  jank git:(transient-vector) ✗ ./build/jank repl
Bottom of clojure.core
> (def a (transient [1 2 3]))
#'clojure.core/a
> (count a)
3
> (get a 1)
2
> (a 1)
2
> (get a -1)
nil
> (a -1)
Exception: Index out of bound; index = -1, count = 3
> (persistent! a)
[1 2 3]
> (count a)
libc++abi: terminating due to uncaught exception of type std::runtime_error: transient used after it's been made persistent
[1]    94093 abort      ./build/jank repl
➜  jank git:(transient-vector) ✗ git status

[Samy-33]

This, because of LSP warning about d not getting moved.