13. Dictionaries

Dictionaries map string keys to values.

13.1 Creating dictionaries

Like vectors, we can create empty dictionaries from type descriptions:

counts: Dict[int]
buckets: Dict[Vec[String]]

Also, we can directly specify the initial key-value pairs:

config := {
    "host": "localhost",
    "port": 8080,
}

commands := {
    "copy": {"overwrite": true, "recursive": false},
    "move": {"overwrite": true, "recursive": true},
}

13.2 Dictionary lookup

Access returns an Option[T], where T is the dictionary value type.

Example:

counts: Dict[int]

counts["apple"] = 3
counts["banana"] = 5

item := counts["apple"]
if item is Some:
    print(item?)
end

missing := counts["orange"]
if missing is None:
    print("no oranges found")
end

Forced lookup is concise with ?:

print(counts["apple"]?)

This throws a runtime error if the key is missing.

13.3 Dictionary iteration

This is achieved using a for loop:

for k, v in counts:
    print("key = ", k, ", value = ", v)
end

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