## Stream: new members

### Topic: why not just open classes

#### Kana (Feb 18 2021 at 18:07):

Why in stdlib a lot of custom selector functions from classes instead of just openings of them?

class has_to_string (α : Type u) :=
(to_string : α → string)

def to_string {α : Type u} [has_to_string α] : α → string :=
has_to_string.to_string


class has_to_string (α : Type u) :=
(to_string : α → string)
open has_to_string


#### Yakov Pechersky (Feb 18 2021 at 18:10):

So that to_string is available everywhere without having to do open has_to_string in your file.

#### Yakov Pechersky (Feb 18 2021 at 18:11):

open is local to the file it is in.

#### kana (Feb 18 2021 at 18:14):

I understood, thanks. Are there any ways to include content of one namespace into current?

#### Eric Wieser (Feb 18 2021 at 18:21):

export perhaps?

Last updated: May 11 2021 at 12:15 UTC