Billed by its creators as “a friendly programming language from the future,” the open source Unison language was founded on the core notion that code is immutable and identified by its content ...

For that to be possible, either you had to cast from mutable to immutable (which you shouldn't have) or the mutable string derives from the immutable string (which it shouldn't have). The latter ...

Extent-local variables would provide a way to share data both within a thread and with child threads in Java, making it easier to reason about data flow.