From: notoria <notoria@users.noreply.github.com>
Date: Sun, 25 May 2025 11:39:31 +0000 (+0200)
Subject: Strengthened `(mod)/2` in CLP(Z)
X-Git-Tag: v0.10.0~43^2
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=4b480a7eab68b4e1dc8d07c36ae7b1645ee073bb;p=scryer-prolog.git

Strengthened `(mod)/2` in CLP(Z)

?- 8 #= -1 mod #Y.
   clpz:(Y in 9..sup), clpz:(-1 mod#Y#=8). % unexpected
Expected: Y = 9
?- 8 #= -12 mod #Y.
   clpz:(Y in 9..sup), clpz:(-12 mod#Y#=8). % unexpected
Expected `Y` with finite domain
---

diff --git a/src/lib/clpz.pl b/src/lib/clpz.pl
index 0f383094..89019b4f 100644
--- a/src/lib/clpz.pl
+++ b/src/lib/clpz.pl
@@ -5110,7 +5110,23 @@ run_propagator(pmod(X,Y,Z), MState) -->
                   YU < X, X =< 0 } -> kill(MState), Z =:= X
             ;   { fd_get(Y, _, n(YL), _, _),
                   YL > X, X >= 0 } -> kill(MState), Z =:= X
-            ;   (   Z > 0 ->
+            ;   (   Z > 0, X < 0 ->
+                    { fd_get(Y, YD, YPs),
+                      YMin is Z+1,
+                      YMax is Z-X,
+                      domain_remove_smaller_than(YD, YMin, YD1),
+                      domain_remove_greater_than(YD1, YMax, YD2) },
+                    fd_put(Y, YD2, YPs)
+                    % queue_goal((Y #> Z, Y #=< Z-X))
+                ;   Z < 0, X > 0 ->
+                    { fd_get(Y, YD, YPs),
+                      YMax is Z-1,
+                      YMin is Z-X,
+                      domain_remove_greater_than(YD, YMax, YD1),
+                      domain_remove_smaller_than(YD1, YMin, YD2) },
+                    fd_put(Y, YD2, YPs)
+                    % queue_goal((Y #< Z, Y #>= Z-X))
+                ;   Z > 0 ->
                     { fd_get(Y, YD, YPs),
                       YMin is Z + 1,
                       domain_remove_smaller_than(YD, YMin, YD1) },