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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Reduction expressions
Date: Tue, 20 Aug 2024 16:41:55 -0700
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Lawrence D'Oliveiro <ldo@nz.invalid> writes:
[...]
> I thought the difference was obvious. “subtype” is the C equivalent of 
> “typedef”, just giving a new name to an existing type. So
>
>     subtype A is B;
>
> (where A and B are simple identifiers) is valid, whereas
>
>     type A is B;
>
> is not: a “type” declaration always creates a new type: you have to write 
> at least
>
>     type A is new B;
>
> and now you have two types with different names that are structurally the 
> same, but not compatible.

A subtype with no added constraint is similar to a C typedef, but given

    subtype Digit is Integer range 0..9;

Digit is distinct from Integer (though they're both the same type).

C doesn't have anything directly corresponding to Ada subtypes.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */