From 55f277e77428d7423ae906a8e1f1324d35b07a7d Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Fri, 4 Mar 2022 12:32:20 -0500
Subject: import Miranda 2.066 from upstream

---
 miralib/ex/set.m | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 miralib/ex/set.m

(limited to 'miralib/ex/set.m')

diff --git a/miralib/ex/set.m b/miralib/ex/set.m
new file mode 100644
index 0000000..c6a52f9
--- /dev/null
+++ b/miralib/ex/set.m
@@ -0,0 +1,64 @@
+||definition of finite sets as an abstract data type, say
+||	%include <ex/set>
+||to include this in one of your own scripts.
+
+abstype set *
+with  makeset::[*]->set * ||converts list to set
+      enum::set *->[*] ||converts set to list
+      empty::set * ||empty set
+      mem::set *->*->bool ||does set contain element?
+      pincludes,includes::set *->set *->bool ||(proper) set inclusion
+      union::[set *]->set * ||union of a list of sets
+      intersect::[set *]->set * ||intersection of a list of sets
+      setdiff::set *->set *->set * ||set difference of two sets
+      union2::set *->set *->set * ||union of two sets
+      intersect2::set *->set *->set * ||intersection of two sets
+      add1::*->set *->set * ||add a single element to a set
+      sub1::*->set *->set * ||remove an element from a set (if present)
+      pick::set *->* ||pick some element from a set
+      rest::set *->set * ||remainder of set, without element got by pick
+      showset::(*->[char])->set *->[char]  ||to make sets printable
+
+set * == [*]        ||a set is represented as a list without duplicates
+makeset = uniq.sort ||for efficiency the lists are kept sorted
+enum = id
+empty = []
+mem (a:x) b = a=b \/ a<b & mem x b
+mem [] b = False
+includes x y = (setdiff y x = [])
+pincludes x y = x~=y & (setdiff y x = [])
+union2 x y = uniq(merge x y)
+union = foldr union2 empty
+setdiff (a:x) (b:y) = a:setdiff x (b:y), if a<b
+                    = setdiff (a:x) y, if a>b
+		    = setdiff x y, otherwise
+setdiff x y = x
+intersect2 (a:x) (b:y) = intersect2 x (b:y), if a<b
+                       = intersect2 (a:x) y, if a>b
+                       = a : intersect2 x y, otherwise
+intersect2 x y = []
+intersect = foldl1 intersect2
+add1 a (b:x) = a:b:x, if a<b
+             = b:x, if a=b
+             = b:add1 a x, otherwise
+add1 a [] = [a]
+sub1 a (b:x) = b:x, if a<b
+             = x, if a=b
+             = b:sub1 a x, otherwise
+sub1 a [] = []
+pick (a:x) = a
+pick [] = error "pick empty"
+rest (a:x) = x
+rest [] = error "pick empty"
+showset f [] = "{}"
+showset f (a:x) = "{"++f a++concat(map g x)++"}"
+                  where
+                  g a = ',':f a
+
+%export -uniq
+||we have used the following auxiliary function, which removes adjacent
+||duplicates from a list  (this is not exported from the script)
+uniq::[*]->[*]
+uniq (a:b:x) = uniq (a:x), if a=b
+             = a:uniq (b:x), otherwise
+uniq x = x
-- 
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