temp_stats.swift in Swift

A week of temperatures: min/max by closure, a bar chart, zip swings.

// Summarize a week of temperature readings: extremes, mean, swings.

import Foundation

let readings: [(day: String, temp: Double)] = [
    ("Mon", -4.0), ("Tue", -1.5), ("Wed", 2.0), ("Thu", 3.5),
    ("Fri", 1.0), ("Sat", -2.5), ("Sun", -6.0),
]

let temps = readings.map { $0.temp }
let coldest = readings.min { $0.temp < $1.temp }!
let warmest = readings.max { $0.temp < $1.temp }!

print("Coldest: \(coldest.day) at \(coldest.temp) C")
print("Warmest: \(warmest.day) at \(warmest.temp) C")
let mean = temps.reduce(0, +) / Double(temps.count)
print(String(format: "Mean: %.1f C", mean))

// Chart each day against the freezing line.
for (day, temp) in readings {
    let length = max(1, Int(temp + 7))
    let bar = String(repeating: "#", count: length)
    let side = temp > 0 ? "above" : "below"
    let label = String(format: "%5.1f", temp)
    print("\(day)  \(label) \(bar) \(side)")
}

// zip against the dropped-first self gives overnight pairs.
let swings = zip(temps, temps.dropFirst()).map { abs($1 - $0) }
print(String(format: "Sharpest overnight swing: %.1f C", swings.max()!))

How it works

1. min and max with closures find the record days.
2. The loop destructures each labeled tuple and charts it.
3. zip(temps, temps.dropFirst()) pairs the overnight changes.

Keywords and builtins used here

• Double
• Foundation
• Int
• String
• abs
• count
• dropFirst
• for
• import
• in
• let
• map
• max
• min
• print
• reduce

The run, in numbers

Lines

30

Characters to type

1066

Tokens

319

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 294 seconds.

Type this snippet

Step 3 of 3 in Encore, step 27 of 27 in Language basics.

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