From 7f65d9e452986fd81b695781dbf482bc65c4a480 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Sun, 8 Apr 2018 07:01:39 +0100
Subject: [PATCH] Fine-tune skeleton-accumulator representations for
 persistency/reuse and for potential speed benefit

---
 syndicate/skeleton.rkt | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/syndicate/skeleton.rkt b/syndicate/skeleton.rkt
index 2723096..0dcf77d 100644
--- a/syndicate/skeleton.rkt
+++ b/syndicate/skeleton.rkt
@@ -50,12 +50,12 @@
 ;;                 (MutableSet Assertion)
 ;;                 (MutableHash SkProj SkAcc))
 ;;       SkAcc = (skeleton-accumulator
-;;                 (MutableSet SkKey)
-;;                 (MutableSet (... -> Any)))
+;;                 (Set SkKey)
+;;                 (MutableSeteq (... -> Any)))
 ;;
 (struct skeleton-continuation (cache table) #:transparent)
 (struct skeleton-matched-constant (cache table) #:transparent)
-(struct skeleton-accumulator (cache handlers) #:transparent)
+(struct skeleton-accumulator ([cache #:mutable] handlers) #:transparent)
 ;;
 ;; A `SkProj` is a *skeleton projection*, a specification of loci
 ;; within a tree-shaped assertion to collect into a flat list.
@@ -111,9 +111,9 @@
   (define cvt (hash-ref! (skeleton-continuation-table c) cs make-hash))
   (define sc (hash-ref! cvt cv make-matched-constant))
   (define (make-accumulator)
-    (skeleton-accumulator (for/mutable-set [(a (skeleton-matched-constant-cache sc))]
+    (skeleton-accumulator (for/set [(a (skeleton-matched-constant-cache sc))]
                             (apply-projection a vs))
-                          (mutable-set)))
+                          (mutable-seteq)))
   (define acc (hash-ref! (skeleton-matched-constant-table sc) vs make-accumulator))
   (set-add! (skeleton-accumulator-handlers acc) h)
   (for [(vars (skeleton-accumulator-cache acc))] (apply-handler! h vars)))
@@ -229,8 +229,7 @@
 (define (add-term-to-skconst! skconst term)
   (set-add! (skeleton-matched-constant-cache skconst) term))
 (define (add-term-to-skacc! skacc vars _term)
-  (define cache (skeleton-accumulator-cache skacc))
-  (set-add! cache vars)
+  (set-skeleton-accumulator-cache! skacc (set-add (skeleton-accumulator-cache skacc) vars))
   (for [(handler (skeleton-accumulator-handlers skacc))]
     (apply handler '+ vars)))
 
@@ -246,8 +245,7 @@
 (define (remove-term-from-skconst! skconst term)
   (set-remove! (skeleton-matched-constant-cache skconst) term))
 (define (remove-term-from-skacc! skacc vars _term)
-  (define cache (skeleton-accumulator-cache skacc))
-  (set-remove! cache vars)
+  (set-skeleton-accumulator-cache! skacc (set-remove (skeleton-accumulator-cache skacc) vars))
   (for [(handler (skeleton-accumulator-handlers skacc))]
     (apply handler '- vars)))