more #H9375 - Rider bargethrough

I think the previous expression would allow moving (via swapping
places) from a pool to solid rock or closed door which was not what
was intended (but moot since there aren't any pools on the Astral
level).  This revised expression does what is intended:  can only
swap to a pool location if already located in/over (the Riders fly?
they should probably be non-breathing) another pool.

diff --git a/src/monmove.c b/src/monmove.c
index c4833c1313815e6f1c64858ccc8d9c6c5dd9efce..35a57e504d045cb7f877f9e3b1c0a494844e0294 100644 (file)
--- a/src/monmove.c
+++ b/src/monmove.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6 monmove.c       $NHDT-Date: 1574475416 2019/11/23 02:16:56 $  $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.114 $ */
+/* NetHack 3.6 monmove.c       $NHDT-Date: 1574530078 2019/11/23 17:27:58 $  $NHDT-Branch: NetHack-3.6 $:$NHDT-Revision: 1.115 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Michael Allison, 2006. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -1625,15 +1625,16 @@ xchar x, y; /* spot 'mtmp' is considering moving to */
         return TRUE;
     }
 
-    /* oversimplification:  creatures that bargethrough can't do so when
-       target monster is in rock or closed door or water (in particular,
-       avoid moving to spots where mondied() won't leave a corpse) */
+    /* oversimplification:  creatures that bargethrough can't swap places
+       when target monster is in rock or closed door or water (in particular,
+       avoid moving to spots where mondied() won't leave a corpse; doesn't
+       matter whether barger is capable of moving to such a target spot if
+       it were unoccupied) */
     if (!accessible(x, y)
-        /* mondied() allows ispool() as an exception to !accessible(),
-           but we'll only do that if both or neither of mtmp's spot and
-           destination spot are water so that we don't swap a water
-           critter onto land or the inverse */
-        && (!is_pool(x, y) ^ !is_pool(mtmp->mx, mtmp->my)))
+        /* mondied() allows is_pool() as an exception to !accessible(),
+           but we'll only do that if 'mtmp' is already at a water location
+           so that we don't swap a water critter onto land */
+        && !(is_pool(x, y) && is_pool(mtmp->mx, mtmp->my)))
         return TRUE;
 
     return FALSE;