in binary operator (Python-like)

[emil14]

See #721

The idea is to have in operator that emits bool and works for lists, dicts and maybe even streams (should probably be overloaded)

Before

lists.Has
---
collection -> has:lst
msg -> has:el
has -> println

After

(msg in collection) -> println

For dict it checks key and for lists it checks value

Questions

• If it works with streams, maybe it should only work with them and for collections we need to explicitly cast them (e.g. via ... (streaming operator) #732) (msg in collection...)
• How well it plays with the HOC that does the same but for more complex cases?
• Is this collide with Dict and List reading syntax #746?