[ new ] added util functions for SortedMap (#3254)

Co-authored-by: G. Allais <guillaume.allais@ens-lyon.org>

CHANGELOG_NEXT.md

@@ -145,6 +145,9 @@ This CHANGELOG describes the merged but unreleased changes. Please see [CHANGELO
 
 * Removed need for the runtime value of the implicit argument in `succNotLTEpred`.
 
+* Added utility functions `insertWith`, `insertFromWith` and `fromListWith` for
+  `SortedMap`.
+
 * Implemented `leftMost` and `rightMost` for `SortedSet`.
 
 * Added `funExt0` and `funExt1`, functions analogous to `funExt` but for functions

CONTRIBUTORS

@@ -80,6 +80,7 @@ troiganto
 Wen Kokke
 Wind Wong
 Zoe Stafford
+Claudio Etterli
 
 Apologies to anyone we've missed - let us know and we'll correct it (or just
 send a PR with the correction).

libs/base/Data/SortedMap.idr

@@ -30,6 +30,15 @@ export
 insert : k -> v -> SortedMap k v -> SortedMap k v
 insert k v = M . insert k v . unM
 
+||| Inserts a key value pair into a map and merges duplicated values
+||| with the given function.
+export
+insertWith : (v -> v -> v) -> k -> v -> SortedMap k v -> SortedMap k v
+insertWith f k v xs =
+  case lookup k xs of
+    Just x  => insert k (f v x) xs
+    Nothing => insert k v xs
+
 public export %inline
 insert' : SortedMap k v -> (k, v) -> SortedMap k v
 insert' = flip $ uncurry insert
@@ -46,6 +55,12 @@ public export %inline
 insertFrom' : Foldable f => SortedMap k v -> f (k, v) -> SortedMap k v
 insertFrom' = flip insertFrom
 
+||| Inserts any foldable of a key value pair into a map and merges duplicated
+||| values with the given function.
+export
+insertFromWith : Foldable f => (v -> v -> v) -> f (k, v) -> SortedMap k v -> SortedMap k v
+insertFromWith f = flip $ foldl $ flip $ uncurry $ insertWith f
+
 export
 delete : k -> SortedMap k v -> SortedMap k v
 delete k = M . delete k . unM
@@ -88,6 +103,12 @@ export
 fromList : Ord k => List (k, v) -> SortedMap k v
 fromList = insertFrom' empty
 
+||| Converts a list of key-value pairs into a map and merges duplicated
+||| values with the given function.
+export
+fromListWith : Ord k => (v -> v -> v) -> List (k, v) -> SortedMap k v
+fromListWith f = flip (insertFromWith f) empty
+
 export
 toList : SortedMap k v -> List (k, v)
 toList = map unDPair . toList . unM