> On Nov 21, 2017, at 6:02 PM, David Hart <da...@hartbit.com> wrote:
>
> Can somebody explain to me what are
> nominal and structural types and why Optional should really be a structural
> type?
Nominal types are structs, enums, protocols and classes. They have declarations
in source and are uniquely identified by their name. Structural types are
functions, meta types, protocol compositions, and tuples.
The distinction is not as clear as you might think because as Chris said, you
can imagine tuple being implemented as ‘struct Tuple<T…>’, similarly functions
and meta types could also be written as such. It is mostly a syntactic
distinction in the language, but it has far-reaching consequences in internal
representations, which is why for now it would be tricky to have structural
types conform to protocols.
Slava
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