well-typed/visualize-cbn

visualize-cbn's Issues

Can it support complex expression like the following?

https://stackoverflow.com/questions/61123307/how-to-print-intermediate-result-in-functor-and-applicative-in-haskell

Indirections

Indirections like on the left can be eliminated. However they can also have circles like on right, so not sure what should be done.

Improving Graph

One of the issues I mentioned at #12
Function applications are indeed unevaluated thunks, however they can have their own layout, like here https://ghc.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/HeapObjects#Genericapplication

For the example above we could have two additional nodes, one for the function and one for 1.

Add graph visualization

An option to create a graph visualization would be tremendously useful.

Confusing error message: "deref: invalid pointer"

$ cat t.hs
span = (\p -> \xs ->
  case xs of {
   Nil -> Pair xs xs ;
   Cons x xs' ->
     if p x then
      let res = @span p xs'
      in Pair (case @res of { Pair ys zs -> Cons x ys})
              (case @res of { Pair ys zs -> zs })
     else Pair Nil xs
  }
)

main = case (@span (\x -> True) (Cons 1 (Cons 2 (Cons 3 Nil)))) of {
  Pair ys zs -> case ys of {
    Cons y ys2 -> ys ;
    Nil -> ys
    }
  }

$ git log -1
commit d8a1ebc0a29d68b5dde8d8fbadd6c85bc47c6a7b
Author: Edsko de Vries <[email protected]>
Date:   Fri Sep 15 17:27:40 2017 +0200

    Add README
$ .cabal-sandbox/bin/visualize-cbn -i t.hs --show-trace --hide-prelude
...
visualize-cbn: deref: invalid pointer Ptr Nothing (Just "res")
CallStack (from HasCallStack):
  error, called at src/CBN/Heap.hs:78:26 in main:CBN.Heap

Show the rule/equation it will use for the next step

For example, in this example from the blog post

Prev Next (step 1, next step: apply enumFromTo)

case enumFromTo 1 3 of { 
      []    -> 0
      x:xs' -> length (1 + 0) xs'
}

It would be very neat to also see the definition of enumFromTo and a note of what the values are. Something like this:

Will apply enumFromTo, with n = 1 and m = 3:
enumFromTo = (\n -> \m ->
  if le n m then Cons n (@enumFromTo (add n 1) m)
            else Nil
)

---

This should probably be a separate feature request but it would also be very helpful to highlight the parts of the code where the rule will be applied. In particular when the next step is selecting a branch of a case expression. To be extra clear, we could highlight the parameters of the rule with different colours.