Experiment with different pointer primitives

[buggymcbugfix]

Mainly ideas from L³ [0] and Fractional Permissions [1]

0: Ahmed, Fluet & Morrisett; 2007; L³: A linear language with locations
1: Makwana & Krishnaswami; 2019; NumLin: Linear Types for Linear Algebra

[buggymcbugfix]

Reminder to self

Prelude> import Foreign.Marshal.Alloc
Prelude Foreign.Marshal.Alloc> :t malloc
malloc :: Foreign.Storable.Storable a => IO (GHC.Ptr.Ptr a)
Prelude Foreign.Marshal.Alloc> p <- malloc @Int
Prelude Foreign.Marshal.Alloc> import Foreign.Ptr
Prelude Foreign.Marshal.Alloc Foreign.Ptr> import Foreign.Storable
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> poke p 0
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> peek p
0
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> let p2 = castPtr @Int @Bool p
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> peek p2
False
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> poke p 1
Prelude Foreign.Marshal.Alloc Foreign.Ptr Foreign.Storable> peek p2
True

[dorchard]

Okay this is now up to date with dev-minor and I started on the evaluator implementation, however I quickly realised that we really need Ben's interfaces/type-classes merged as well so that we can restrict the types of things that can go inside pointers. We don't want to allow arbitrary things (like functions or suspended effectful computations!) Another alternative is that we restrict the pointers just to integers at the moment.
So this remains in flux.