[ base ] Data.SortedSet.leftMost and .rightMost (#3260)

* [ base ] Data.SortedSet.leftMost and .rightMost Implement `leftMost` and `rightMost` for `SortedSet` in terms of the functions with the same name in `Data.SortedMap`. * contributors --------- Co-authored-by: G. Allais <guillaume.allais@ens-lyon.org>
idris-lang · Jun 5, 2024 · f83ad9c · f83ad9c
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diff --git a/CHANGELOG_NEXT.md b/CHANGELOG_NEXT.md
@@ -139,6 +139,8 @@ This CHANGELOG describes the merged but unreleased changes. Please see [CHANGELO
 
 * Removed need for the runtime value of the implicit argument in `succNotLTEpred`.
 
+* Implemented `leftMost` and `rightMost` for `SortedSet`.
+
 * Added `funExt0` and `funExt1`, functions analogous to `funExt` but for functions
   with quantities 0 and 1 respectively.
 

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
@@ -57,6 +57,7 @@ Nicolas Biri
 Niklas Larsson
 Ohad Kammar
 Peter Hajdu
+Ricardo Prado Cunha
 Robert Walter
 rhiannon morris
 Rodrigo Oliveira

diff --git a/libs/base/Data/SortedSet.idr b/libs/base/Data/SortedSet.idr
@@ -62,6 +62,16 @@ export
 intersection : (x, y : SortedSet k) -> SortedSet k
 intersection x y = difference x (difference x y)
 
+||| Returns the leftmost (least) value
+export
+leftMost : SortedSet k -> Maybe k
+leftMost (SetWrapper m) = fst <$> leftMost m
+
+||| Returns the rightmost (greatest) value
+export
+rightMost : SortedSet k -> Maybe k
+rightMost (SetWrapper m) = fst <$> rightMost m
+
 export
 Ord k => Semigroup (SortedSet k) where
   (<+>) = union