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authorGravatar Adam Chlipala <adam@chlipala.net>2018-12-14 15:26:21 -0500
committerGravatar Adam Chlipala <adam@chlipala.net>2018-12-14 15:26:21 -0500
commit720e1cb2c84dfd274fcbfd7bf4974a1c110501cb (patch)
tree643890450a4a2231e7aa2971fa73f776943bdc33
parent6d87f78102bba77bc090ca3fb105597d3ce3748f (diff)
List.assocAddSorted
-rw-r--r--lib/ur/list.ur16
-rw-r--r--lib/ur/list.urs3
2 files changed, 19 insertions, 0 deletions
diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 0da9316e..10877420 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -479,6 +479,22 @@ fun assocAdd [a] [b] (_ : eq a) (x : a) (y : b) (ls : t (a * b)) =
None => (x, y) :: ls
| Some _ => ls
+fun assocAddSorted [a] [b] (_ : eq a) (_ : ord a) (x : a) (y : b) (ls : t (a * b)) =
+ let
+ fun aas (ls : t (a * b)) (acc : t (a * b)) =
+ case ls of
+ [] => rev ((x, y) :: acc)
+ | (x', y') :: ls' =>
+ if x' = x then
+ revAppend ((x, y) :: acc) ls'
+ else if x < x' then
+ revAppend ((x, y) :: acc) ls
+ else
+ aas ls' ((x', y') :: acc)
+ in
+ aas ls []
+ end
+
fun recToList [a ::: Type] [r ::: {Unit}] (fl : folder r)
= @foldUR [a] [fn _ => list a] (fn [nm ::_] [rest ::_] [[nm] ~ rest] x xs =>
x :: xs) [] fl
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index c5c279b7..c1d46022 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -109,6 +109,9 @@ val assoc : a ::: Type -> b ::: Type -> eq a -> a -> t (a * b) -> option b
val assocAdd : a ::: Type -> b ::: Type -> eq a -> a -> b -> t (a * b) -> t (a * b)
+val assocAddSorted : a ::: Type -> b ::: Type -> eq a -> ord a -> a -> b -> t (a * b) -> t (a * b)
+(* Assume the list is already sorted in ascending order and maintain that ordering. *)
+
(** Converting records to lists *)
val recToList : a ::: Type -> r ::: {Unit} -> folder r -> $(mapU a r) -> t a