Still some bugs in rules generated from rule-language source. However,

a great deal does work.

src/mw_engine/core.clj

@@ -39,8 +39,15 @@
    exception is thrown, cache its message on the cell and set state to error"
   [cell world rules]
   (try
-    (apply-rules cell world rules)
+    (merge 
-    (catch Exception e (merge {:state :error :error (.getMessage e)} cell)))) 
+      (apply-rules cell world rules) 
+      {:generation (+ (or (:generation cell) 0) 1)})
+    (catch Exception e 
+      (merge cell {:error 
+                   (format "%s at generation %d when in state %s"
+                           (.getMessage e)
+                           (:generation cell)
+                           (:state cell))})))) 
  
 (defn- transform-world-row
   "Return a row derived from this row of this world by applying these rules to each cell."

src/mw_engine/natural_rules.clj

@@ -147,7 +147,7 @@
      (fn [cell world]
        (cond (and (= (:state cell) :new) (> (get-int cell :altitude) snowline)) (merge cell {:state :snow})))
      ;; in between, we have a wasteland.
-     (fn [cell world] (cond (= (:state cell) :new) (merge cell {:state :waste}))
+     (fn [cell world] (cond (= (:state cell) :new) (merge cell {:state :grassland}))
      )))
 
 (def natural-rules (flatten

src/mw_engine/utils.clj

@@ -88,10 +88,13 @@
     * `cell` a cell within that world;
     * `depth` an integer representing the distance from [x,y] that
       should be searched;
-    * `property` a keyword representing a property of the neighbours.
+    * `property` a keyword representing a property of the neighbours;
-    * `value` a value of that property"
+    * `value` a value of that property;
-  ([world x y depth property value comparator]
+    * `op` a comparator function to use in place of `=`.
-    (filter #(apply comparator (list (get % property) value)) (get-neighbours world x y depth)))
+
+   It gets messy."
+  ([world x y depth property value op]
+    (filter #(eval (list op (get % property) value)) (get-neighbours world x y depth)))
   ([world x y depth property value]
     (get-neighbours-with-property-value world x y depth property value =))
   ([world cell depth property value]