JuniorTheoryCommon

What does the program print?

SWIFT

let words = ["to", "be", "or", "not", "to", "be"]
var counts: [String: Int] = [:]
for word in words {
    counts[word, default: 0] += 1
}
print(counts["be", default: 0], counts.count)

2 4

Expecting 1 4: reading default: 0 as "set the count to 0". The default is used only while the key is missing; after that += 1 adds to the stored count.
Expecting 2 6: taking count for the number of words added. A dictionary counts pairs, and a repeated word updates its pair instead of adding one.

What does counts["is", default: 0] return here, and does counts.count change after it?
Why does counts[word] += 1 without default: not compile?

Back to questions Open topic in roadmap →Answer it yourself — Quiz

Back to questions

JuniorTheoryCommon

What does the program print?

SWIFT

let words = ["to", "be", "or", "not", "to", "be"]
var counts: [String: Int] = [:]
for word in words {
    counts[word, default: 0] += 1
}
print(counts["be", default: 0], counts.count)

2 4

Expecting 1 4: reading default: 0 as "set the count to 0". The default is used only while the key is missing; after that += 1 adds to the stored count.
Expecting 2 6: taking count for the number of words added. A dictionary counts pairs, and a repeated word updates its pair instead of adding one.

What does counts["is", default: 0] return here, and does counts.count change after it?
Why does counts[word] += 1 without default: not compile?

Back to questions Open topic in roadmap →Answer it yourself — Quiz