yes, i know. but there is nothing that stops you from writing pure functions, and quite a lot of features that encourage it, even if they are not checked by the compiler. i'd probably like a c++ compiler that warned me about lack of purity, but as the article says, sometimes you have to bite the bullet.
> there is nothing that stops you from writing pure functions
If they are not checked, they will be forgotten. When reading a function, if I do not have the guarantee that it is pure, it means the same as an old comment (not much).
If the only way to enforce it is convention and force of will it will not be enforced.
As an exaggerated illustration: we might add a "without-bugs" annotation to a function, to indicate it has no bugs. After all, nothing stops you from writing bug-free functions :)
