Here is some code that typechecks:
implement add_heads(a,b) =
case (a,b) of
| (~None_vt(),g) => g
| (l, ~None_vt()) => l
| (~Some_vt(~nested(~Some_vt(~list_vt_cons(x,xs)))),
~Some_vt(~nested(~Some_vt(~list_vt_cons(y,ys))))) =>
(free(xs); Some_vt(nested(Some_vt(list_vt_cons(x+y,ys)))))
Some warnings are issued due to non-exhaustiveness of pattern matching
involved.
On Tue, May 15, 2018 at 10:27 PM, aditya siram <aditya.si...@gmail.com>
wrote:
>
> #include "share/atspre_staload.hats"
>
> datavtype nested = nested of (Option_vt(List_vt(int)))
>
> extern fun add_heads(
> a : Option_vt(nested),
> b : Option_vt(nested)
> ): Option_vt(nested)
>
> implement add_heads(a,b) =
> case (a,b) of
> | (~None_vt(),g) => g
> | (l, ~None_vt()) => l
> | (Some_vt(nested(Some_vt(list_vt_cons(x,_)))),
> Some_vt(nested(Some_vt(list_vt_cons(y,ys))))) =>
> Some_vt(nested(Some_vt(list_vt_cons(x+y,ys))))
>
> implement main0(argc,argv) = ()
>
>
> The above is a minimal non-compiling example from a larger program. I even
> tried adding '@' to the pattern match with 'fold@' in the body but it
> didn't work.
>
> Thanks!
>
> On Tuesday, May 15, 2018 at 8:28:33 PM UTC-5, gmhwxi wrote:
>>
>> Oops. I am NOT so clear ...
>>
>> On Tue, May 15, 2018 at 9:27 PM, Hongwei Xi <gmh...@gmail.com> wrote:
>>
>>> I am so clear as to what you need precisely.
>>>
>>> Could you show me how to do it using pattern matching repeatly?
>>> Then I may be able to do it using a nested pattern.
>>>
>>> Here is an example that may be useful:
>>>
>>> | ~Some_vt(~Some_vt(xs as list_vt_cons _)) => // using xs here
>>>
>>> The two Some_vt constructors are freed but list_vt_cons is not.
>>>
>>> On Tue, May 15, 2018 at 9:04 PM, aditya siram <aditya...@gmail.com>
>>> wrote:
>>>
>>>> Hi all,
>>>> I'm sure there's an easy answer to this but I'm not having much luck.
>>>> How do I destructure into a view type that nested in another viewtype? For
>>>> example, I'd to pattern match on something of type
>>>> 'Option_vt(Option_vt(list_vt int))'. I'm not having much luck doing it in
>>>> one fell swoop like: ' | Some_vt(Some_vt(list_vt_cons(x, xs))) => ...'
>>>> especially when the linear proof of some inner value (like 'x') needs to be
>>>> preserved.
>>>>
>>>> Thanks!
>>>>
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>>>>
>>>
>>>
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