Comments (4)
If the type class changes as I suggest in #5 then most of these objections change in nature - so I suggest we resolve that before coming back to this.
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The GraphWithFastRemoveVertex
seems a bit grim - you end up with N classes. And note that removeVertex
isn't O(n) - it's only that if you use something with constant time construction for all operations, and only works if you start with a GraphMonad
.
I think there is potential value in putting a small number of carefully chosen operations in the class, which can be implemented 100% generically, but for certain classes of graph are vastly more efficient. The other option is to say they are only implemented in a few choice data types, typically imported qualified, and people are expected to convert.
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The
GraphWithFastRemoveVertex
seems a bit grim - you end up with N classes.
I think there is potential value in putting a small number of carefully chosen operations in the class
@ndmitchell Shall we list the candidates here? I'm starting to think that there are not that many of them. The removeVertex
operation does seem to make sense for all inhabitants of the Graph
type class, because it corresponds to the vertex
method. But removeEdge
on the other hand is already problematic, because some instances, like ToList
would find it awkward to have it, even though they can implement it very efficiently as a no-op. Note, there is no explicit notion of edges in the type class itself.
Is there any other candidate to bring N above 1? :)
P.S.: For various newtype's like GraphFunctor
the requirement to also handle removeVertex
is actually a burden. Presumably, this will become a common theme: the larger the core, the more often one needs to handle cases that may be irrelevant for the task at hand.
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After a lot of refactoring, we ended up with the API where each Graph
instance defines a bunch of custom functions, such as isEmpty
, hasVertex
, vertices
, removeVertex
, and many others, which all have different complexity characteristics.
See: http://hackage.haskell.org/package/algebraic-graphs/docs/Algebra-Graph.html
Making all of them part of the core type class seems to be an overkill.
I guess we can close this issue for now. If there is a proposal to create a more feature-rich type class, with complete graph manipulation API (say, as defined in Algebra.Graph
), we can create a separate issue.
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Related Issues (20)
- Hackage Release HOT 5
- How to handle goodness inherited from other libraries HOT 2
- Bump upper bound for base-compat for version 0.4 on Hackage HOT 4
- Unable to use ghcid HOT 6
- Algorithms should be in terms of typeclasses not data structures HOT 15
- Acyclic graphs with Int labels HOT 5
- Tests failed to build with QuickCheck 2.14.2
- Multitree HOT 3
- Monoid instance HOT 6
- support for GraphViz "HTML strings" for node or edge labels HOT 1
- Add benchmarks to CI HOT 2
- Supporting different node and edge types HOT 7
- v0.6 fails to build with GHC 8.0 and 8.2 HOT 3
- Doubt about decorating a Graph HOT 4
- Compatibility with mtl-2.3 HOT 2
- Smart constructor for Symbol rather than requiring -XOverloadedLists HOT 1
- Proposal : foldgM HOT 2
- Algebra.Graph.Labelled.AdjacencyMap.edges appears to be broken HOT 2
- Semigroup version of Algebra.Graph.Labelled.AdjacencyMap HOT 7
- Bump "deepseq" dependency bounds to 1.5.0.0 HOT 2
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