WIP: add prerequisites to practice exercises

[cmcaine]

Closes #314.

I've done the first few and welcome feedback on whether they're okay.

As I'm sure you know, we don't have enough concepts in config.json to do this at the moment.

Even including all the ones in the concepts dir, we're still missing a concepts for:

• loops
• exceptions
• common data structures (dicts, vectors, sets, tuples) (I wonder if there should be a parent concept of "common data structures" to avoid revealing which ones to use?)
• structs
• bitwise operators

I've just picked likely names and put them in prerequisites without adding them elsewhere.

There's also the issue of multiple solutions to problems. Should I add a concept as a prereq if it is commonly used in correct solutions, or only if it is required?

And I'm assuming I should avoid adding concepts that are parents of concepts that are required.

[SaschaMann]

Thanks!

Overall this looks good but I don't have good answers to all the questions you raised yet.

I've just picked likely names and put them in prerequisites without adding them elsewhere.

Yep, we can create those later. Knowing which ones we need is quite helpful.

(I wonder if there should be a parent concept of "common data structures" to avoid revealing which ones to use?)

I think if there's one clearly preferable structure to use, it's fine to add that as a pre-req. But it might be useful to have a less-specific container for more advanced exercises so that students learn when to use which structure. @iHiD do you have thoughts on this?

There's also the issue of multiple solutions to problems. Should I add a concept as a prereq if it is commonly used in correct solutions, or only if it is required?

This was discussed on the call today but unfortunately I forgot what the conclusion was (there were a few suggestions)... I'll have to check the VoD once it's up :D

I think any concept that's required to understand the "top" exemplar solution, i.e. the one we currently recommended first in mentoring notes and not one of the performance-optimised solutions, should definitely be a pre-req.

And I'm assuming I should avoid adding concepts that are parents of concepts that are required.

Yes. I don't think it would break anything but there's no need to have them.

[SaschaMann]

Suggested change

	"boolean-logic", "loops",
	"boolean-logic", "loops", "sets"

This gives away the solution but I guess it may still make sense to have it as pre-req?

[cmcaine]

That's the question, I guess. You don't need to use sets to solve this (and many students solve it without sets). Sets are just the most elegant solution.

But this one is perfectly fine, so I don't think I'd want to discourage solutions like this:

ispangram2(input) = all(in(lowercase(input)), 'a':'z')

This is why I think a data-structures or iterables concept might be a good idea?

[cmcaine]

I've resolved the merge conflicts.

I don't know how all of this interacts with us not having concept exercises turned on. Maybe we should move all of these prerequisites to practices or something instead?