[Prelude] listToCombi(naisons), thanks to Quentin, authors of this nice function.

src/Gargantext/Database/Metrics/NgramsByNode.hs

@@ -147,9 +147,7 @@ getCoocByNgramsOnly cId nt ngs = do
                                          <$> Map.lookup t1 ngs'
                                          <*> Map.lookup t2 ngs'
                        )
-                      | (t1,t2) <- list2combi $ Map.keys ngs']
-                        where
-                          list2combi = undefined
+                      | (t1,t2) <- listToCombi identity $ Map.keys ngs']
 
 getNodesByNgramsOnlyUser :: CorpusId -> NgramsType -> [Text] -> Cmd err (Map Text (Set NodeId))
 getNodesByNgramsOnlyUser cId nt ngs = fromListWith (<>) <$> map (\(n,t) -> (t, Set.singleton n))

src/Gargantext/Prelude.hs

@@ -258,3 +258,8 @@ zipSnd f xs = zip xs (f xs)
 maximumWith :: (Ord a1, Foldable t) => (a2 -> a1) -> t a2 -> a2
 maximumWith f = L.maximumBy (compare `on` f)
 
+
+-- | To get all combinations of a list with no repetition and apply a function to the resulting list of pairs
+listToCombi :: forall a b. (a -> b) -> [a] -> [(b,b)]
+listToCombi f l = [ (f x, f y) | (x:rest) <- L.tails l,  y <- rest ]
+