Concept exercise suggestions

Some first thoughts on matching exercises to concepts.
Languages in parentheses are tracks we could perhaps port from.

| **Concept** | **Possible exercises** |
| ------------------ | ------------------------------------------ |
| basics | lasagna (PR #1079) |
| booleans | pacman-rules (draft PR #1081) |
| numbers (_wip: Colin_) | freelancer-rates? (C++, Elixir, JS, Swift)
assembly-line? (jq, Ruby)
currency-exchange (Python, Julia) |
| includes-headers (draft PR #1084) | doctor-data? (C++) |
| conditionals | vehicle-purchase? (C++, Go, JS, jq, Swift)
cars-assemble? (Clojure, C#, F#, Go, Java, Lua, Julia) |
| loops | interest-is-interesting? (C++, Clojure, Crystal, C#, F#, Go)
mixed-juices? (JS, Julia) |
| pointers | election-day? (Go)
speedywagon-foundation? (C++) |
| arrays | making-the-grade? (C++, Python)
bird-watcher? (Clojure, C#, F#, Go, Java, JS, Julia) |
| strings | log-levels? (C++, Elixir, Clojure, CLisp, C#, F#, Gleam, Java, Python, Julia) |
| blocks | task-handler? (Crystal) |
| bits | secrets? (Crystal, Elixir, Gleam, Java, Julia) |
| enums | boutique-inventory? (Elixir, Gleam, Ruby) |
| scope | ???? |

I already started `pacman-rules`.

I haven't yet had time to go through Bob's concept docs in detail, and review all the potential exercises on other tracks to see how well they match.

If anyone gets enthusiastic about this, maybe pick an exercise you like, let us know (to avoid duplication), then port it to C?

Figuring out how to sequence the concepts in a syllabus is another challenge... (and I suppose I should call it a DAG when talking to CS experts)