diff --git a/project.clj b/project.clj
index b0f37c9..c966484 100644
--- a/project.clj
+++ b/project.clj
@@ -1,5 +1,5 @@
 (defproject mw-parser "0.1.0-SNAPSHOT"
-  :description "FIXME: write description"
+  :description "Parser for production rules for MicroWorld engine"
   :url "http://example.com/FIXME"
   :license {:name "Eclipse Public License"
             :url "http://www.eclipse.org/legal/epl-v10.html"}
diff --git a/src/mw_parser/core.clj b/src/mw_parser/core.clj
index 6680125..48f27ae 100644
--- a/src/mw_parser/core.clj
+++ b/src/mw_parser/core.clj
@@ -1,15 +1,18 @@
 ;; A very simple parser which parses production rules of the following forms:
 ;;
-;; "if altitude is less than 100 and state is forest then state should be climax and deer should be 3"
-;; "if altitude is 100 or fertility is 25 then state should be heath and fertility should be 24.3"
-;; "if altitude is 100 or fertility is 25 then state should be heath"
-;; "if deer is more than 2 and wolves is 0 and fertility is more than 20 then deer should be deer + 2"
-;; "if deer is more than 1 and wolves is more than 1 then deer should be deer - wolves"
+;; * "if altitude is less than 100 and state is forest then state should be climax and deer should be 3"
+;; * "if altitude is 100 or fertility is 25 then state should be heath and fertility should be 24.3"
+;; * "if altitude is 100 or fertility is 25 then state should be heath"
+;; * "if deer is more than 2 and wolves is 0 and fertility is more than 20 then deer should be deer + 2"
+;; * "if deer is more than 1 and wolves is more than 1 then deer should be deer - wolves"
+;; * "if state is grassland and 4 neighbours have state equal to water then state should be village"
 ;;
-;; It should also but does not yet parse rules of the form
-;; "if 6 neighbours have state is water then state should be fishery"
-;; "if state is forest or state is climax and some neighbours have state is fire then 3 in 5 chance that state should be fire"
-;; "if state is pasture and more than 3 neighbours have state is scrub then state should be scrub"
+;; It should also but does not yet parse rules of the form:
+
+;; * "if 6 neighbours have state is water then state should be fishery"
+;; * "if state is forest or state is climax and some neighbours have state is fire then 3 in 5 chance that state should be fire"
+;; * "if state is pasture and more than 3 neighbours have state is scrub then state should be scrub"
+;; * "if state is forest and fertility is between 55 and 75 then state should be climax"
 ;;
 ;; it generates rules in the form expected by mw-engine.core
 
@@ -21,99 +24,239 @@
 (declare parse-not-condition)
 (declare parse-simple-condition)
 
+;; a regular expression which matches string representation of numbers
+(def re-number #"^[0-9.]*$")
+
+(defn keyword-or-numeric
+  "If this token appears to represent an explicit number, return that number;
+   otherwise, make a keyword of it and return that."
+  [token]
+  (cond 
+    (re-matches re-number token) (read-string token)
+    (keyword? token) token
+    true (keyword token)))
+
+;; Generally all functions in this file with names beginning 'parse-' take a 
+;; sequence of tokens (and in some cases other optional arguments) and return a
+;; vector comprising
+;;
+;; # A code fragment parsed from the front of the sequence of tokens, and
+;; # the remaining tokens which were not consumed in constructing that sequence.
+;;
+;; In every case if the function cannot parse the desired construct from the
+;; front of the sequence of tokens it returns nil.
+
+(defn parse-numeric-value
+  "Parse a number."
+  [[value & remainder]]
+  (if (re-matches re-number value) [(read-string value) remainder]))
+
+(defn parse-property-int
+  "Parse a token assumed to be the name of a property of the current cell, 
+  whose value is assumed to be an integer."
+  [[value & remainder]]
+  (if value [(list 'get-int 'cell (keyword value)) remainder]))
+
+(defn parse-property-value
+  "Parse a token assumed to be the name of a property of the current cell."
+  [[value & remainder]]
+  (if value [(list (keyword value) 'cell) remainder]))
+
+(defn parse-simple-value
+  "Parse a value from the first of these `tokens`. If `expect-int` is true, return
+   an integer or something which will evaluate to an integer."
+  ([tokens expect-int]
+    (or
+        (parse-numeric-value tokens)
+        (cond expect-int
+          (parse-property-int tokens)
+          true (parse-property-value tokens))))
+  ([tokens]
+    (parse-simple-value tokens false)))
+
+(defn parse-disjunct-value
+  "Parse a list of values from among these `tokens`. If `expect-int` is true, return
+   an integer or something which will evaluate to an integer.
+
+   NOTE: contrary to the general behaviour of `parse-` functions, this one
+   returns a vector [nil unconsumed-tokens] when it cannot find any further
+   disjuncts. TODO: doesn't work."
+  [[OR & tokens] expect-int]
+  (cond 
+    (member? OR '("in" "or"))
+    (cond expect-int
+      (let [[member r] (parse-simple-value tokens)
+            [others remainder] (parse-disjunct-value r expect-int)]
+        (cond member [(cons member others) remainder])
+        true
+        (let [[member r] tokens
+              [others remainder] (parse-disjunct-value r expect-int)]
+          (cond member [(cons (keyword member) others) remainder]
+            true [(list member) r]))))
+    true [nil (cons OR tokens)]))
+    
+(defn parse-value 
+  "Parse a value from among these `tokens`. If `expect-int` is true, return
+   an integer or something which will evaluate to an integer."
+  ([tokens expect-int]
+    (or 
+      (parse-disjunct-value tokens expect-int)
+      (parse-simple-value tokens)))
+  ([tokens]
+    (parse-value tokens false)))
+
+(defn parse-member-condition
+  [[property IN & rest]]
+  (if (= IN "in")
+    (let [[l & remainder] (parse-disjunct-value (cons "in" rest) false)]
+      [(list 'member? (keyword property) l) remainder])))
+
 (defn parse-less-condition
-  "Parse '[property] is less than [value]."
-  [[property is less than value & rest]]
-  (cond (and (member? is '("is" "are")) (= less "less") (= than "than"))
+  "Parse '[property] less than [value]'."
+  [[property LESS THAN value & rest]]
+  (cond (and (= LESS "less") (= THAN "than"))
         [(list '< (list 'get-int 'cell (keyword property)) (read-string value)) rest]))
 
 (defn parse-more-condition
-  "Parse '[property] is more than [value]."
-  [[property is more than value & rest]]
-  (cond (and (member? is '("is" "are")) (= more "more") (= than "than"))
+  "Parse '[property] more than [value]'."
+  [[property MORE THAN value & rest]]
+  (cond (and (= MORE "more") (= THAN "than"))
         [(list '> (list 'get-int 'cell (keyword property)) (read-string value)) rest]))
 
-(defn parse-is-condition
-  "Parse clauses of the form 'x is y', but not 'x is more than y' or 'x is less than y'.
-   It is necessary to disambiguate whether value is a numeric or keyword."
-  [[property is value & rest]]
-  (cond (and (member? is '("is" "are"))
-             (not (member? value '("more" "less" "exactly" "not"))))
-        [(cond
-          (re-matches #"^[0-9.]*$" value)(list '= (list 'get-int 'cell (keyword property)) (read-string value))
-          true (list '= (list (keyword property) 'cell) (keyword value)))
-         rest]))
+(defn parse-between-condition
+  [[p BETWEEN v1 AND v2 & rest]]
+  (cond (and (= BETWEEN "between") (= AND "and") (not (nil? v2)))
+    (let [property (first (parse-simple-value (list p) true))
+          value1 (first (parse-simple-value (list v1) true))
+          value2 (first (parse-simple-value (list v2) true))]
+      [(list 'or
+            (list '< value1 property value2)
+            (list '> value1 property value2)) rest])))
 
-(defn parse-not-condition [[property is not & rest]]
-  (cond (and (member? is '("is" "are")) (= not "not"))
-        (let [partial (parse-simple-condition (cons property (cons is rest)))]
-          (cond partial
-                (let [[condition remainder] partial]
-                  [(list 'not condition) remainder])))))
+(defn parse-is-condition
+  "Parse clauses of the form 'x is y', 'x is in y or z...', 
+   'x is between y and z', 'x is more than y' or 'x is less than y'.
+   It is necessary to disambiguate whether value is a numeric or keyword."
+  [[property IS value & rest]]
+  (cond 
+    (member? IS '("is" "are"))
+    (let [tokens (cons property (cons value rest))]
+      (cond 
+        (= value "in") (parse-member-condition tokens)
+        (= value "between") (parse-between-condition tokens)
+        (= value "more") (parse-more-condition tokens)
+        (= value "less") (parse-less-condition tokens)
+        (re-matches re-number value) [(list '= (list 'get-int 'cell (keyword property)) (read-string value)) rest]
+        value [(list '= (list (keyword property) 'cell) (keyword value)) rest]))))
+
+(defn parse-not-condition 
+  "Parse the negation of a simple condition."
+  [[property IS NOT & rest]]
+  (cond (and (member? IS '("is" "are")) (= NOT "not"))
+    (let [partial (parse-simple-condition (cons property (cons "is" rest)))]
+      (cond partial
+        (let [[condition remainder] partial]
+          [(list 'not condition) remainder])))))
+
+(defn gen-neighbours-condition
+  [comparator quantity property value remainder] 
+  [(list comparator quantity 
+         (list 'count
+               (list 'get-neighbours-with-property-value 'world 'cell 
+                     (keyword property) (keyword-or-numeric value))))
+           remainder])
+
+(defn parse-simple-neighbours-condition
+  [[n NEIGHBOURS have-or-are & rest]]
+  (let [quantity (first (parse-numeric-value (list n)))]       
+    (cond
+      (and quantity (= NEIGHBOURS "neighbours"))
+      (cond
+        (= have-or-are "are") 
+        (let [[value & remainder] rest]
+          (gen-neighbours-condition '= quantity :state value remainder))
+        (= have-or-are "have")
+        (let [[property EQUAL TO value & remainder] rest]
+          (cond (and (= EQUAL "equal") (= TO "to"))
+            (gen-neighbours-condition '= quantity property value remainder)))))))
+  
+(defn parse-neighbours-condition
+  "Parse conditions referring to neighbours"
+  [tokens]
+  (or
+    (parse-simple-neighbours-condition tokens)
+;;    (parse-more-than-neighbours-condition tokens)
+;;    (parse-fewer-than-neighbours-condition tokens)
+    ))
 
 (defn parse-simple-condition
   "Parse conditions of the form '[property] [comparison] [value]'."
   [tokens]
-  (or (parse-is-condition tokens)
-      (parse-not-condition tokens)
-      (parse-less-condition tokens)
-      (parse-more-condition tokens)))
+  (or
+    (parse-simple-neighbours-condition tokens)
+    (parse-member-condition tokens)
+    (parse-not-condition tokens)
+    (parse-is-condition tokens)
+    (parse-less-condition tokens)
+    (parse-more-condition tokens)))
 
 (defn parse-disjunction-condition
-  "Parse '... or [condition]' from `tokens`, there `left` is the already parsed first disjunct."
-  [left tokens]
-  (let [partial (parse-conditions tokens)]
-    (if
-       partial
-           (let [[right remainder] partial]
-             [(list 'or left right) remainder]))))
-
-(defn parse-conjunction-condition
-  "Parse '... and [condition]' from `tokens`, there `left` is the already parsed first conjunct."
+  "Parse '... or [condition]' from `tokens`, where `left` is the already parsed first disjunct."
   [left tokens]
   (let [partial (parse-conditions tokens)]
     (if partial
-           (let [[right remainder] partial]
-             [(list 'and left right) remainder]
-           ))))
+      (let [[right remainder] partial]
+        [(list 'or left right) remainder]))))
+
+(defn parse-conjunction-condition
+  "Parse '... and [condition]' from `tokens`, where `left` is the already parsed first conjunct."
+  [left tokens]
+  (let [partial (parse-conditions tokens)]
+    (if partial
+      (let [[right remainder] partial]
+        [(list 'and left right) remainder]))))
 
 (defn parse-conditions
   "Parse conditions from `tokens`, where conditions may be linked by either 'and' or 'or'."
   [tokens]
   (let [partial (parse-simple-condition tokens)]
     (if partial
-           (let [[left [next & remainder]] partial]
-             (cond
-              (= next "and") (parse-conjunction-condition left remainder)
-              (= next "or") (parse-disjunction-condition left remainder)
-              true partial)
-              ))))
+      (let [[left [next & remainder]] partial]
+        (cond
+          (= next "and") (parse-conjunction-condition left remainder)
+          (= next "or") (parse-disjunction-condition left remainder)
+          true partial)))))
 
 (defn parse-left-hand-side
  "Parse the left hand side ('if...') of a production rule."
-  [tokens]
-  (if
+ [tokens]
+ (if
    (= (first tokens) "if")
    (parse-conditions (rest tokens))))
 
-(defn parse-arithmetic-action [previous [prop1 should be prop2 operator value & rest]]
+(defn parse-arithmetic-action 
+  "Parse actions of the form '[property] should be [property] [arithmetic-operator] [value]',
+   e.g. 'fertility should be fertility + 1', or 'deer should be deer - wolves'."
+  [previous [prop1 should be prop2 operator value & rest]]
   (if (and (= should "should")
            (= be "be")
            (member? operator '("+" "-" "*" "/")))
     [(list 'merge (or previous 'cell)
            {(keyword prop1) (list (symbol operator) (list 'get-int 'cell (keyword prop2))
                                   (cond
-                                     (re-matches #"^[0-9.]*$" value) (read-string value)
-                                     true (list 'get-int 'cell (keyword value))))}) rest]))
+                                    (re-matches re-number value) (read-string value)
+                                    true (list 'get-int 'cell (keyword value))))}) rest]))
 
-(defn parse-set-action [previous [property should be value & rest]]
+(defn parse-set-action 
+  "Parse actions of the form '[property] should be [value].'"
+  [previous [property should be value & rest]]
   (if (and (= should "should") (= be "be"))
     [(list 'merge (or previous 'cell)
-           {(keyword property) (cond (re-matches #"^[0-9.]*$" value) (read-string value) true (keyword value))}) rest]))
+           {(keyword property) (cond (re-matches re-number value) (read-string value) true (keyword value))}) rest]))
 
 (defn parse-simple-action [previous tokens]
-    (or (parse-arithmetic-action previous tokens)
-        (parse-set-action previous tokens)))
+  (or (parse-arithmetic-action previous tokens)
+      (parse-set-action previous tokens)))
 
 (defn parse-actions
   "Parse actions from tokens."
@@ -130,7 +273,9 @@
   (if (= (first tokens) "then")
     (parse-actions nil (rest tokens))))
 
-(defn parse-rule [line]
+(defn parse-rule 
+  "Parse a complete rule from this string or sequence of string tokens."
+  [line]
   (cond
    (string? line) (parse-rule (split (triml line) #"\s+"))
    true (let [[left remainder] (parse-left-hand-side line)
diff --git a/test/mw_parser/core_test.clj b/test/mw_parser/core_test.clj
index dd1b44a..a294f99 100644
--- a/test/mw_parser/core_test.clj
+++ b/test/mw_parser/core_test.clj
@@ -1,7 +1,20 @@
 (ns mw-parser.core-test
+  (:use mw-engine.utils)
   (:require [clojure.test :refer :all]
             [mw-parser.core :refer :all]))
 
-(deftest a-test
-  (testing "FIXME, I fail."
-    (is (= 0 1))))
+
+(deftest rules-tests
+  (testing "if altitude is less than 100 and state is forest then state should be climax and deer should be 3"
+           (is (parse-rule "if altitude is less than 100 and state is forest then state should be climax and deer should be 3"))
+           (is (let [cell (apply (eval (parse-rule "if altitude is less than 100 and state is forest then state should be climax and deer should be 3"))
+                                 (list {:state :forest :altitude 99} nil))]
+                 (and (= (:state cell) :climax) (= (:deer cell) 3))))
+           ))
+          
+
+;; * "if altitude is 100 or fertility is 25 then state should be heath and fertility should be 24.3"
+;; * "if altitude is 100 or fertility is 25 then state should be heath"
+;; * "if deer is more than 2 and wolves is 0 and fertility is more than 20 then deer should be deer + 2"
+;; * "if deer is more than 1 and wolves is more than 1 then deer should be deer - wolves"
+;;
\ No newline at end of file