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by ratorx 89 days ago
Making it explicit wouldn’t be particularly problematic no? Option<&Spouse> in Rust terms. Or for this specific case, a GADT (Single | Married<&Spouse>)?

It could even use a special “NULL” address. Just don’t pollute every type with it.
1 comments
adrian_b 89 days ago
Polluting every type with it is just a very bad implementation which has nothing in common with the concept of NULL as proposed by Tony Hoare in the paper "Record Handling".

The concept as proposed by Hoare is strictly necessary for things like partial relations, which are encountered very frequently in practice.

It is true however that a large number of programming languages have misused the concept of a NULL reference proposed by Hoare.

As you say, there must be distinct types that may have or may not have a "nothing" value.

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mrkeen 89 days ago
> The concept as proposed by Hoare is strictly necessary for things like partial relations

I read the 'Partial Functional Relationships' section. There's nothing special there. It's just structs with nulls.

> Polluting every type with it I think you're reacting to the pollution of the syntax. Hoare already polluted the semantics: Every type can be null. You can't even model a NonNull<Spouse> because NonNull itself can be null.

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