Null Pointer Pattern

[Carter Schonwald]

That’s a really nice idea !

On Tue, Aug 18, 2020 at 2:54 AM Henning Thielemann <
lemming at henning-thielemann.de> wrote:

>
>
> On Mon, 17 Aug 2020, Carter Schonwald wrote:
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>
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> > There’s an interesting idea or two in here.  Like, should we support
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> > having non-nullable pointers?
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>
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> That was my first idea, too.
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> newtype NonNullPtr a = NonNullPtr (Ptr a)
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>
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> maybeNonNull :: Ptr a -> Maybe (NonNullPtr a)
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> Using NonNullPtr in FFI declarations would make the interfaces safer.
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>
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> E.g.
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>     dst <- mallocArray n
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>     for (maybeNonNull dst) $ \dstNonNull ->
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>        copyArray dstNonNull srcNonNull n
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>
>
> That seems better than testing for nullPtr and then forgeting this
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> information in the type, again.
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