From 68cde5be6c77b2da57aea975950e5c481b0b220d Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Thu, 12 May 2016 22:18:57 -0400
Subject: [PATCH] DemandMatcher: overlap not ruled out! Remove it.

---
 js/src/demand-matcher.js            |  9 +++++++++
 racket/syndicate/demand-matcher.rkt | 28 ++++++++++++++++++++++------
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/js/src/demand-matcher.js b/js/src/demand-matcher.js
index c6cdd55..900c285 100644
--- a/js/src/demand-matcher.js
+++ b/js/src/demand-matcher.js
@@ -107,6 +107,15 @@ DemandMatcher.prototype.handlePatch = function (p) {
   var addedSupply = this.extractKeys(p.added, self.supplyProjections, sN, 'supply');
   var removedSupply = this.extractKeys(p.removed, self.supplyProjections, sN, 'supply');
 
+  // Though the added and removed sets of patches are always disjoint,
+  // *after projection* this may not hold. Cancel out any overlaps.
+  var demandOverlap = addedDemand.intersect(removedDemand);
+  var supplyOverlap = addedSupply.intersect(removedSupply);
+  addedDemand = addedDemand.subtract(demandOverlap);
+  removedDemand = removedDemand.subtract(demandOverlap);
+  addedSupply = addedSupply.subtract(supplyOverlap);
+  removedSupply = removedSupply.subtract(supplyOverlap);
+
   self.currentSupply = self.currentSupply.union(addedSupply);
   self.currentDemand = self.currentDemand.subtract(removedDemand);
 
diff --git a/racket/syndicate/demand-matcher.rkt b/racket/syndicate/demand-matcher.rkt
index 2f212c5..71dee26 100644
--- a/racket/syndicate/demand-matcher.rkt
+++ b/racket/syndicate/demand-matcher.rkt
@@ -51,6 +51,15 @@
                   (set)
                   (set)))
 
+(define (ensure-non-wild s kind spec direction t)
+  (when (not s)
+    (error 'demand-matcher
+           "Wildcard ~a of ~v ~a:\n~a"
+           kind
+           spec
+           direction
+           (trie->pretty-string t))))
+
 ;; DemandMatcher (Constreeof Action) Patch -> (Transition DemandMatcher)
 ;; Given a Patch from the environment, projects it into supply and
 ;; demand increase and decrease sets. Calls ChangeHandlers in response
@@ -69,12 +78,19 @@
   (define-values (added-supply removed-supply)
     (patch-project/set #:take supply-arity p supply-spec))
 
-  (when (not added-demand) (error 'demand-matcher "Wildcard demand of ~v:\n~a"
-                                  demand-spec
-                                  (trie->pretty-string (patch-added p))))
-  (when (not added-supply) (error 'demand-matcher "Wildcard supply of ~v:\n~a"
-                                  supply-spec
-                                  (trie->pretty-string (patch-added p))))
+  (ensure-non-wild added-demand 'demand demand-spec 'added (patch-added p))
+  (ensure-non-wild added-supply 'supply supply-spec 'added (patch-added p))
+  (ensure-non-wild removed-demand 'demand demand-spec 'removed (patch-removed p))
+  (ensure-non-wild removed-supply 'supply supply-spec 'removed (patch-removed p))
+
+  ;; Though the added and removed sets of patches are always disjoint,
+  ;; *after projection* this may not hold. Cancel out any overlaps.
+  (let ((overlap (set-intersect added-demand removed-demand)))
+    (set! added-demand (set-subtract added-demand overlap))
+    (set! removed-demand (set-subtract removed-demand overlap)))
+  (let ((overlap (set-intersect added-supply removed-supply)))
+    (set! added-supply (set-subtract added-supply overlap))
+    (set! removed-supply (set-subtract removed-supply overlap)))
 
   (set! supply (set-union supply added-supply))
   (set! demand (set-subtract demand removed-demand))