Deprecate Keyword.get/3 and Keyword.pop/3

[josevalim]

The reason is to avoid the semantic difference between Keyword.get(opts, :foo, :bar) and opts[:foo] || :bar. The latter is preferable because often we don't care about making a distinction between the absence of a value and that value being set to nil.

It is also debatable if we should deprecate similar functions from Enum.

[ericmj]

How are you going to make a distinction between false and nil?

[josevalim]

Possibly Keyword.bool/2 will help with that. That's one of the pending issues to be solved.

[whatyouhide]

Why deprecate Keyword.pop/3 though? You mean turning it into Keyword.pop/2 and using it like

{val, kw} = Keyword.pop(kw, :my_val)
val || :default

?

[josevalim]

@whatyouhide I am not sure on pop yet. It theoretically suffers from the same issue but it cannot be expressed as concisely as get. Let's wait for more feedback before we start working on any of those changes. :)

[josevalim]

We should also look into adding a lazy_put (only puts a value is not there lazily). We need a small overhaul in the Dict API overall.