Highlighting unused parameters?

[kfisler]

I'm seeing several cases of teachers getting confused when going from examples to functions, and not actually using their parameters in their code (the code refers to the constant on which they developed the example).

When they hit run, it might help to flag/highlight parameters that aren't used. Is that a useful general addition to CPO?

[blerner]

This can't be a CPO issue -- it's a semantic issue that requires compiler support to detect which names are unused. And it's a subtle idea: more generally, should we flag names that aren't ever used? Just function parameters? Some other heuristic?

Or, is this confusion a useful teaching moment, "Why aren't my Foo flags displaying differently from Bar flags?"

[kfisler]

I figured it was at least partly a CPO issue from the perspective of potential visual-clutter.

It is of course a teaching moment while we are in the room. I'm trying to help them for the times when we are not in the room.

[blerner]

(I'm imagining this to be similar to the "Halloween highlighting" in drracket for non-executed code, that appears once you hit Run and disappears when you edit the code.) A counterargument for this, after seeing various BS:* functions: Sam the butterfly, some physics functions, etc, deliberately take in x and y parameters and use only one of them. It would be decidedly annoying for students to be unable to eliminate the "this parameter isn't used" warning highlighting without making their program incorrect.