From 62dfceb86ba7dfbabb0fabaf89c9cbc8d08afc32 Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adam@chlipala.net>
Date: Tue, 12 Feb 2019 11:05:48 -0500
Subject: List.mapConcat and mapConcatM

---
 lib/ur/list.ur  | 20 ++++++++++++++++++++
 lib/ur/list.urs |  4 ++++
 2 files changed, 24 insertions(+)

(limited to 'lib')

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index b38097b7..848bbd5f 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -101,6 +101,16 @@ fun mp [a] [b] f =
         mp' []
     end
 
+fun mapConcat [a] [b] f =
+    let
+        fun mapConcat' acc ls =
+            case ls of
+                [] => rev acc
+              | x :: ls => mapConcat' (revAppend (f x) acc) ls
+    in
+        mapConcat' []
+    end
+
 fun mapi [a] [b] f =
     let
         fun mp' n acc ls =
@@ -153,6 +163,16 @@ fun mapM [m ::: (Type -> Type)] (_ : monad m) [a] [b] f =
         mapM' []
     end
 
+fun mapConcatM [m] (_ : monad m) [a] [b] f =
+    let
+        fun mapConcatM' acc ls =
+            case ls of
+                [] => return (rev acc)
+              | x :: ls' => ls <- f x; mapConcatM' (revAppend ls acc) ls'
+    in
+        mapConcatM' []
+    end
+
 fun mapMi [m ::: (Type -> Type)] (_ : monad m) [a] [b] f =
     let
         fun mapM' i acc ls =
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index 7e3cf205..6df2d5d9 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -20,6 +20,10 @@ val append : a ::: Type -> t a -> t a -> t a
 
 val mp : a ::: Type -> b ::: Type -> (a -> b) -> t a -> t b
 
+val mapConcat : a ::: Type -> b ::: Type -> (a -> t b) -> t a -> t b
+
+val mapConcatM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type -> (a -> m (t b)) -> t a -> m (t b)
+
 val mapPartial : a ::: Type -> b ::: Type -> (a -> option b) -> t a -> t b
 
 val mapi : a ::: Type -> b ::: Type -> (int -> a -> b) -> t a -> t b
-- 
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