Ages 15–18 · Grades 9–12 · Computer Science

KindForge

A red type error isn’t the compiler being difficult — it’s the compiler catching a bug before your code ever runs. Here you read a short program and predict what the compiler will say: will it compile? If it does, what will it print? If it doesn’t, fix it — without changing what it was meant to do. Some fixes compile but do the wrong thing; the goal is the one that does both.

The code is a teaching subset of the Swift language; the programs are original teaching examples. Runs on your device — nothing leaves it.

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