Dictionaries

Dictionaries (dicts) are key-value stores. Keys are always strings; values can be any type.

Creating dictionaries

let person = {"name": "Alice", "age": 30, "active": true}
let empty = {}

Accessing values

Use bracket notation with a string key:

let name = person["name"]     // "Alice"
let age = person["age"]       // 30

Accessing a missing key returns none (no error):

let email = person["email"]
print(email)    // none

Modifying values

person["age"] = 31             // update existing key
person["email"] = "a@b.com"   // add new entry

Methods

Practical examples

Counting occurrences

let words = ["apple", "banana", "apple", "cherry", "banana", "apple"]
let counts = {}
for word in words {
  if counts.has(word) {
    counts[word] += 1
  } else {
    counts[word] = 1
  }
}

for key in counts {
  print(key + ": " + str(counts[key]))
}

Storing structured data

let point = {"x": 10, "y": 20}
let x = str(point["x"])
let y = str(point["y"])
print("Position: ({x}, {y})")

Iterating over entries

let config = {"width": 800, "height": 600, "title": "My App"}
for key in config {
  let val = str(config[key])
  print(key + ": " + val)
}

Checking for a key before using it

let settings = {"volume": 80}

if settings.has("volume") {
  let v = str(settings["volume"])
  print("Volume is {v}")
} else {
  print("Using default volume")
}