Re:Lisp and Haskell (2015)
by rxhernandez on Thursday October 08, 2020 @06:48AM
(#24717864)
Is null even a type though? If not, then it would seem it's not a static type system that's solving it; it's something else entirely solving it (whether or not that something is contained in that specific type system).
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| on HN ]
The issue with null, as commonly implemented, is that null is a value that inhabits all types. So in that sense it is a defect of the type system.
In Common Lisp, T is the "any" type (which makes sense there, as type specifiers can be formed using unions using (or type-A type-B ...) lists), the value NIL is the sole instance of the type NULL.