15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.
A collection stores related values. The loop visits 1, 2, and 3, updating the total from 0 to 1, then 3, then 6. Record this trace rather than guessing. Identify the first and last valid positions in this language: Pascal can declare a 1-based array, while many other examples use zero-based containers. Add another value and update the bounds correctly. Explain what an empty collection should produce.
let introduces an immutable binding and var a mutable one. Converting text with Int(raw) may produce nil. if let unwraps a present value without force-unwrapping missing data.
let minutes = [1, 2, 3]
var total = 0
for value in minutes { total += value }
print(total)
Expected result: 6
Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.