Perform an operation on every item of a list, e.g.
for the list ["ox", "cat", "deer", "whale"] calculate
the list of sizes of the strings, e.g. [2, 3, 4, 5]
fsharp1.9.9.9
let lengths = List.map String.length ["ox"; "cat"; "deer"; "whale"]
let lengths = List.map String.length ["ox"; "cat"; "deer"; "whale"]