primitive Bool is Stringable
new create(from: Bool) => from
fun eq(y: Bool): Bool => this == y
fun ne(y: Bool): Bool => this != y
fun op_and(y: Bool): Bool => this and y
fun op_or(y: Bool): Bool => this or y
fun op_xor(y: Bool): Bool => this xor y
fun op_not(): Bool => not this
fun string(): String iso^ =>
(if this then "true" else "false" end).string()