[Haskell] ANN: Haskell bindings for the igraph C library
Nils Schweinsberg
mail at nils.cc
Mon Dec 17 14:38:49 CET 2012
Am 16.12.2012 20:24, schrieb Jason Dagit:
> How does this compare with fgl? http://hackage.haskell.org/package/fgl
FGL is a pure Haskell library while our haskell-igraph package uses the
foreign function interface to run all graph-related calculations in C
the C library igraph (I haven't implemented any graph algorithms). The
runtime performance with our igraph library should be the same as if
you'd be using the native C library (if you ignore the small
Haskell->C->Haskell overhead).
It is also seems to be more of a higher level library. As user you don't
have to worry about node-IDs/labels or whether your graph is "static" or
not (in the FGL context). Using features like GADTs and type
families/associated types it is possible to keep track of informations
like whether or not your graph is directed/weighted or not, while in FGL
all graphs are by default directed and unweighted. Consider for example
edges :: Graph d a -> [Edge d a]
-- directed, unweighted graph
g :: Graph D a
-- undirected, weighted graph
w :: Graph (Weighted U) a
which leads to
edges g :: [Edge D a]
edges w :: [Edge (Weighted U) a]
or even functions like
toUndirected :: (IsDirected d, E (ToUndirected d) a)
=> Graph d a
-> Graph (ToUndirected d) a
toDirected :: (IsUndirected u, E (ToDirected u) a)
=> Graph u a
-> Graph (ToDirected u) a
which evaluate to
toUndirected g :: Graph U a
toDirected w :: Graph (Weighted D) a
This is even revertable, and `toDirected . toUndirected == id` while the
FGL function `undir` simply adds all missing edges and loses track of
what the original/directed graph looked like.
Maybe George has more details on why he wanted to use igraph instead of FGL.
- Nils
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