How to get type info?

Questions / Help
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9

The first element of a keyword list of arbitrary length was proving difficult for me to pattern match against.

Ex:

iex(1)> foo = [ok: :one, ok: :two, ok: :three]       

iex(2)> inspect(foo, structs: false)
"[ok: :one, ok: :two, ok: :three]"

It seems like this is just a list, but:

iex(3)> [ok: _ | bosh] = foo
** (CompileError) iex:3: misplaced operator |/2

i/1 revealed that it’s really a list of two element tuples:

iex(4)> i(foo) 
Term
  [ok: :one, ok: :two, ok: :three]
Data type
  List
Description
  This is what is referred to as a "keyword list". A keyword list is a list
  of two-element tuples where the first element of each tuple is an atom.
Reference modules
  Keyword, List
Implemented protocols
  Collectable, Enumerable, IEx.Info, Inspect, List.Chars, String.Chars

With this crucial clarification:

iex(5)> [{:ok, _} | bosh] = foo               
[ok: :one, ok: :two, ok: :three]

iex(6)> bosh
[ok: :two, ok: :three]

Which brings us full circle by to my original query: