Print, unpack, and use tuple keys

Print several values with spaces between them. Unpack an owned list when its length is known; the list must contain exactly as many elements as targets. The statement moves its elements, and _ discards an element.

def main() -> Result[(), AllocError | IoError | OverflowError[i64]]:
    first, second = "north east".split(" ")?
    print(first, second, 2)?
    mut visits = dict[(i64, i64), i64].new()?
    cell = (3, 4)
    *visits.get_or_insert(cell, 0)? += 1
    *visits.get_or_insert(cell, 0)? += 1
    print(visits.get(cell, 0))?
    visited = {(3, 4), (3, 4), (4, 3)}?
    print(len(visited), cell in visited)?
    Ok(())

north east 2
2
2 True

Tuple keys contain integers, booleans, strings, or further tuples of those types. Values compare by their contents; a grid coordinate needs no integer encoding or string allocation. get_or_insert starts a missing count at 0 and returns a reference to the stored count; see dictionaries.

Consume dictionary values directly when the dictionary is finished:

def main() -> Result[(), AllocError | IoError]:
    groups = {"first": [1, 2]?, "second": [3]?}?
    for group in groups.into_values()?:
        print(group)?
    Ok(())

[1, 2]
[3]

into_values() consumes the dictionary and transfers its owned values into an ordered list. Use copy(groups)? first if the original is still needed.