[siebenschlaefer]

Currently school::roster() and school::grade() can be implemented as
non-const methods. Logically it makes sense to be able to call those two
methods on a const instance because they should not modify that
instance.

[siebenschlaefer]

I accidentally deleted my previous (identical) PR.

[arcuru]

The CI is failing because of this. We test against Clang 3.8 since last I checked it was still the default in something (probably an Ubuntu LTS build, 16.XX?). For now we should support that until we update the compilers, so you'd need to add a default constructor to the example.

I would suggest actually adding a brief comment to the added constructor to explain why there is otherwise unnecessary code.

This is a good change though :)

[siebenschlaefer]

Good catch!
I could add a defaulted default constructor (as you suggested) or I could could use value initialization for those three const grade_school::school instances (see https://godbolt.org/z/Mrx2uh).
Which do you prefer?

[arcuru]

Wow that's...interesting. Let's do value initialization as you suggested so we don't force the students to deal with that.