These functions and predicates implement the standard library for working with option types. Note that option type support is still incomplete.
Declarations in this section:
Test if x is absent (always returns false)
Test if x is absent
Return value of x if x is not absent. Aborts when evaluated on absent value.
Return value x unchanged (since x is guaranteed to be non-optional).
Test if x is not absent (always returns true)
Test if x is not absent