That's interesting. I wonder if a future Elixir version could have a way of defining macros which sould emit these optimizations. Is this a likely direction for future developments?
> "with" needs to be implemented as a special form as it has different lexical properties than a bunch of nested cases.
Could you expand on this a little? What are those different lexical properties?
To do so, we would need to compile to core, and that means tools like Cover and the Erlang debugger would no longer work with Elixir. It is unlikely we will go to this direction.
> Could you expand on this a little? What are those different lexical properties?
If you compile a "with" to a bunch of cases, a variable from the outer case would be available to both success and failure cases. Take this code:
a = true
with true <- a = false do
a
else
_ -> a
end
a = true
case a = false do
true -> a
_ -> a
end
This is not true.
We have only two variadic special forms: "for" and "with".
"for" needs to be implemented as a special form as it emits some optimizations that are only available at the Core Erlang level.
"with" needs to be implemented as a special form as it has different lexical properties than a bunch of nested cases.
None of those could be implemented with macros.
Regarding whitespace sensitiveness, most languages have subtle issues, to varying degrees but especially if you have optional line terminators. Although it is true one or two extra cases appear in Elixir due to optional parentheses.