to_map

In std/seq.

fn to_map<K, V>(self: Collection<T>, key: T -> K, value: T -> V) : Map<K, V>

A map from the key of each value of self to its value; two values with one key are an evaluation error: ["bb", "a"] | to_map(s => s, s => size(s)) is Map {"bb": 2, "a": 1}.