Typed lists and hashes

For those cases where you want to ensure all values in a list conform to a type, you can construct it like this.

$list = List<Num>()

And use it normally...

$list.push(1, 2, "three")

The last element there is quietly ignored since it doesn't fit the type. And since you know the list allows only numbers, you can now safely do this.

$list.sum   # 3

For hashes, you can specify types for both the keys and values.

$hash = Hash<Str, Num>()
$hash["one"] = 1
$hash["two"] = 2
$hash[3]     = "three"  # ignored

Of course, this works for ordered hashes too.