[CodeMage]

> Most often it is not necessary, and not wanted, to enforce a and b having the same type.

That really depends on what you're trying to do. Presenting these two different declarations as somehow equivalent is very misleading and I'm glad that the author didn't do that.

[ncmncm]

They are not presented as equivalent, but as a choice.

The author's failing was in presenting neither of them until long after they were due, and presenting thoroughly inferior alternatives in the meantime.