diff --git a/src/cljs/mw3/parser.cljs b/src/cljs/mw3/parser.cljs
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+(ns mw-parser.declarative
+  (:use mw-engine.utils
+        [clojure.string :only [split trim triml]])
+  (:require [instaparse.core :as insta]))
+
+
+;; error thrown when an attempt is made to set a reserved property
+(def reserved-properties-error
+  "The properties 'x' and 'y' of a cell are reserved and should not be set in rule actions")
+;; error thrown when a rule cannot be parsed. Slots are for
+;; (1) rule text
+;; (2) cursor showing where in the rule text the error occurred
+;; (3) the reason for the error
+(def bad-parse-error "I did not understand:\n'%s'\n%s\n%s")
+
+
+(def grammar
+  ;; in order to simplify translation into other natural languages, all
+  ;; TOKENS within the parser should be unambiguous
+  "RULE := IF SPACE CONDITIONS SPACE THEN SPACE ACTIONS;
+   CONDITIONS := DISJUNCT-CONDITION | CONJUNCT-CONDITION | PROPERTY-CONDITION | NEIGHBOURS-CONDITION ;
+   DISJUNCT-CONDITION := CONDITION SPACE OR SPACE CONDITIONS;
+   CONJUNCT-CONDITION := CONDITION SPACE AND SPACE CONDITIONS;
+   CONDITION := NEIGHBOURS-CONDITION | PROPERTY-CONDITION;
+   WITHIN-CONDITION := NEIGHBOURS-CONDITION SPACE WITHIN SPACE NUMERIC-EXPRESSION;
+   NEIGHBOURS-CONDITION := WITHIN-CONDITION | QUANTIFIER SPACE NEIGHBOURS SPACE IS SPACE PROPERTY-CONDITION | QUANTIFIER SPACE NEIGHBOURS IS EXPRESSION | QUALIFIER SPACE NEIGHBOURS-CONDITION;
+   PROPERTY-CONDITION := PROPERTY SPACE QUALIFIER SPACE EXPRESSION;
+   EXPRESSION := SIMPLE-EXPRESSION | RANGE-EXPRESSION | NUMERIC-EXPRESSION | DISJUNCT-EXPRESSION | VALUE;
+   SIMPLE-EXPRESSION := QUALIFIER SPACE EXPRESSION | VALUE;
+   DISJUNCT-EXPRESSION := IN SPACE DISJUNCT-VALUE;
+   RANGE-EXPRESSION := BETWEEN SPACE NUMERIC-EXPRESSION SPACE AND SPACE NUMERIC-EXPRESSION;
+   NUMERIC-EXPRESSION := VALUE | VALUE SPACE OPERATOR SPACE NUMERIC-EXPRESSION;
+   NEGATED-QUALIFIER := QUALIFIER SPACE NOT | NOT SPACE QUALIFIER;
+   COMPARATIVE-QUALIFIER := IS SPACE COMPARATIVE SPACE THAN;
+   QUALIFIER := COMPARATIVE-QUALIFIER | NEGATED-QUALIFIER | EQUIVALENCE | IS SPACE QUALIFIER;
+   QUANTIFIER := NUMBER | SOME | NONE | ALL | COMPARATIVE SPACE THAN SPACE NUMBER;
+   EQUIVALENCE := IS SPACE EQUAL | EQUAL | IS ;
+   COMPARATIVE := MORE | LESS;
+   DISJUNCT-VALUE := VALUE | VALUE SPACE OR SPACE DISJUNCT-VALUE;
+   IF := 'if';
+   THEN := 'then';
+   THAN := 'than';
+   OR := 'or';
+   NOT := 'not';
+   AND := 'and';
+   SOME := 'some';
+   NONE := 'no';
+   ALL := 'all'
+   BETWEEN := 'between';
+   WITHIN := 'within';
+   IN := 'in';
+   MORE := 'more';
+   LESS := 'less' | 'fewer';
+   OPERATOR := '+' | '-' | '*' | '/';
+   NEIGHBOURS := 'neighbour' | 'neighbor' | 'neighbours' | 'neighbors';
+   PROPERTY := SYMBOL;
+   VALUE := SYMBOL | NUMBER;
+   EQUAL := 'equal to';
+   IS := 'is' | 'are' | 'have' | 'has';
+   NUMBER := #'[0-9]+' | #'[0-9]+.[0-9]+';
+   SYMBOL := #'[a-z]+';
+   ACTIONS := ACTION | ACTION SPACE 'and' SPACE ACTIONS
+   ACTION := SIMPLE-ACTION | PROBABLE-ACTION;
+   PROBABLE-ACTION := VALUE SPACE 'chance in' SPACE VALUE SPACE SIMPLE-ACTION;
+   SIMPLE-ACTION := SYMBOL SPACE BECOMES SPACE EXPRESSION
+   BECOMES := 'should be'
+   SPACE := #' *'"
+  )
+
+(defn TODO
+  "Marker to indicate I'm not yet finished!"
+  [message]
+  message)
+
+
+(declare generate simplify)
+
+(defn suitable-fragment?
+  "Return `true` if `tree-fragment` appears to be a tree fragment of the expected `type`."
+  [tree-fragment type]
+  (and (coll? tree-fragment)(= (first tree-fragment) type)))
+
+(defn assert-type
+  "If `tree-fragment` is not a tree fragment of the expected `type`, throw an exception."
+  [tree-fragment type]
+  (assert (suitable-fragment? tree-fragment type)
+          (throw (Exception. (format "Expected a %s fragment" type)))))
+
+(defn generate-rule
+  "From this `tree`, assumed to be a syntactically correct rule specification,
+  generate and return the appropriate rule as a function of two arguments."
+  [tree]
+  (assert-type tree :RULE)
+  (list 'fn ['cell 'world] (list 'if (generate (nth tree 2)) (generate (nth tree 3)))))
+
+(defn generate-conditions
+  "From this `tree`, assumed to be a syntactically correct conditions clause,
+  generate and return the appropriate clojure fragment."
+  [tree]
+  (assert-type tree :CONDITIONS)
+  (generate (nth tree 1)))
+
+(defn generate-condition
+  [tree]
+  (assert-type tree :CONDITION)
+  (generate (nth tree 1)))
+
+(defn generate-conjunct-condition
+  [tree]
+  (assert-type tree :CONJUNCT-CONDITION)
+  (list 'and (generate (nth tree 1))(generate (nth tree 3))))
+
+(defn generate-disjunct-condition
+  [tree]
+  (assert-type tree :DISJUNCT-CONDITION)
+  (list 'or (generate (nth tree 1))(generate (nth tree 3))))
+
+(defn generate-ranged-property-condition
+  "Generate a property condition where the expression is a numeric range"
+  [tree property expression]
+  (assert-type tree :PROPERTY-CONDITION)
+  (assert-type (nth tree 3) :RANGE-EXPRESSION)
+  (let [l1 (generate (nth expression 2))
+        l2 (generate (nth expression 4))
+        pv (list property 'cell)]
+    (list 'let ['lower (list 'min l1 l2)
+                'upper (list 'max l1 l2)]
+          (list 'and (list '>= pv 'lower)(list '<= pv 'upper)))))
+
+(defn generate-disjunct-condition
+  "Generate a property condition where the expression is a disjunct expression"
+  [tree property qualifier expression]
+  (let [e (list 'some (list 'fn ['i] '(= i value)) (list 'quote expression))]
+    (list 'let ['value (list property 'cell)]
+          (if (= qualifier '=) e
+            (list 'not e)))))
+
+(defn generate-property-condition
+  ([tree]
+   (assert-type tree :PROPERTY-CONDITION)
+   (generate-property-condition tree (first (nth tree 3))))
+  ([tree expression-type]
+   (assert-type tree :PROPERTY-CONDITION)
+   (let [property (generate (nth tree 1))
+         qualifier (generate (nth tree 2))
+         expression (generate (nth tree 3))]
+     (case expression-type
+       :DISJUNCT-EXPRESSION (generate-disjunct-condition tree property qualifier expression)
+       :RANGE-EXPRESSION (generate-ranged-property-condition tree property expression)
+       (list qualifier (list property 'cell) expression)))))
+
+(defn generate-simple-action
+  [tree]
+  (assert-type tree :SIMPLE-ACTION)
+  (let [property (generate (nth tree 1))
+        expression (generate (nth tree 3))]
+    (if (or (= property :x) (= property :y))
+      (throw (Exception. reserved-properties-error))
+      (list 'merge 'cell {property expression}))))
+
+(defn generate-multiple-actions
+   [tree]
+  nil)
+;;   (assert (and (coll? tree)(= (first tree) :ACTIONS)) "Expected an ACTIONS fragment")
+;;   (conj 'do (map
+
+(defn generate-disjunct-value
+  "Generate a disjunct value. Essentially what we need here is to generate a
+  flat list of values, since the `member` has already been taken care of."
+  [tree]
+  (assert-type tree :DISJUNCT-VALUE)
+  (if (= (count tree) 4)
+    (cons (generate (second tree)) (generate (nth tree 3)))
+    (list (generate (second tree)))))
+
+(defn generate-numeric-expression
+  [tree]
+  (assert-type tree :NUMERIC-EXPRESSION)
+  (case (first (second tree))
+    :SYMBOL (list (keyword (second (second tree))) 'cell)
+    (generate (second tree))))
+
+(defn generate-neighbours-condition
+  "Generate code for a condition which refers to neighbours."
+  ([tree]
+   (generate-neighbours-condition tree (first (second tree))))
+  ([tree quantifier-type]
+   (let [quantifier (second (second tree))
+         pc (generate (nth tree 4))]
+     (case quantifier-type
+       :NUMBER (generate-neighbours-condition '= (read-string quantifier) pc 1)
+       :SOME (generate-neighbours-condition '> 0 pc 1)
+       :QUANTIFIER
+       (let [comparative (generate (simplify (second quantifier)))
+             value (simplify (nth quantifier 5))]
+         (generate-neighbours-condition comparative value pc 1)))))
+  ([comp1 quantity property-condition distance]
+   (list comp1
+         (list 'count (list 'remove false (list 'map (list 'fn ['cell] property-condition) '(get-neighbours cell world distance)))) quantity))
+  ([comp1 quantity property-condition]
+   (generate-neighbours-condition comp1 quantity property-condition 1)))
+
+;; (def s1 "if 3 neighbours have state equal to forest then state should be forest")
+;; (def s2 "if some neighbours have state equal to forest then state should be forest")
+;; (def s3 "if more than 3 neighbours have state equal to forest then state should be forest")
+;; (def s4 "if fewer than 3 neighbours have state equal to forest then state should be forest")
+;; (def s5 "if all neighbours have state equal to forest then state should be forest")
+;; (def s6 "if more than 3 neighbours within 2 have state equal to forest then state should be forest")
+
+;; (nth (simplify (parse-rule s1)) 2)
+;; (second (nth (simplify (parse-rule s1)) 2))
+;; (nth (simplify (parse-rule s2)) 2)
+;; (map simplify (nth (simplify (parse-rule s2)) 2))
+;; ;; (second (nth (simplify (parse-rule s2)) 2))
+;; ;; (nth (simplify (parse-rule s3)) 2)
+;; (second (nth (simplify (parse-rule s3)) 2))
+;; (map simplify (second (nth (simplify (parse-rule s3)) 2)))
+;; ;; (nth (simplify (parse-rule s4)) 2)
+;; ;; (second (nth (simplify (parse-rule s4)) 2))
+;; ;; (nth (simplify (parse-rule s5)) 2)
+;; ;; (second (nth (simplify (parse-rule s5)) 2))
+;; ;; (nth (simplify (parse-rule s6)) 2)
+;; ;; (second (nth (simplify (parse-rule s6)) 2))
+
+;; ;; (generate (nth (nth (simplify (parse-rule s5)) 2) 4))
+;; ;; (generate (nth (simplify (parse-rule s2)) 2))
+;; ;; (generate (nth (simplify (parse-rule s1)) 2))
+
+
+;; (generate-neighbours-condition '= 3 '(= (:state cell) :forest) 1)
+;; (generate-neighbours-condition (nth (simplify (parse-rule s3)) 2))
+;; (generate-neighbours-condition (nth (simplify (parse-rule s2)) 2))
+;; (generate-neighbours-condition (nth (simplify (parse-rule s1)) 2))
+
+
+(defn generate
+  "Generate code for this (fragment of a) parse tree"
+  [tree]
+  (if
+    (coll? tree)
+    (case (first tree)
+      :ACTIONS (generate-multiple-actions tree)
+      :COMPARATIVE (generate (second tree))
+      :COMPARATIVE-QUALIFIER (generate (nth tree 2))
+      :CONDITION (generate-condition tree)
+      :CONDITIONS (generate-conditions tree)
+      :CONJUNCT-CONDITION (generate-conjunct-condition tree)
+      :DISJUNCT-CONDITION (generate-disjunct-condition tree)
+      :DISJUNCT-EXPRESSION (generate (nth tree 2))
+      :DISJUNCT-VALUE (generate-disjunct-value tree)
+      :EQUIVALENCE '=
+      :EXPRESSION (generate (second tree))
+      :LESS '<
+      :MORE '>
+      :NEGATED-QUALIFIER (case (generate (second tree))
+                                 = 'not=
+                                 > '<
+                                 < '>)
+      :NEIGHBOURS-CONDITION (generate-neighbours-condition tree)
+      :NUMERIC-EXPRESSION (generate-numeric-expression tree)
+      :NUMBER (read-string (second tree))
+      :PROPERTY (list (generate (second tree)) 'cell) ;; dubious - may not be right
+      :PROPERTY-CONDITION (generate-property-condition tree)
+      :QUALIFIER (generate (second tree))
+      :RULE (generate-rule tree)
+      :SIMPLE-ACTION (generate-simple-action tree)
+      :SYMBOL (keyword (second tree))
+      :VALUE (generate (second tree))
+      (map generate tree))
+    tree))
+
+
+(defn simplify-qualifier
+  "Given that this `tree` fragment represents a qualifier, what
+   qualifier is that?"
+  [tree]
+  (cond
+    (empty? tree) nil
+    (and (coll? tree)
+         (member? (first tree) '(:EQUIVALENCE :COMPARATIVE))) tree
+    (coll? (first tree)) (or (simplify-qualifier (first tree))
+                             (simplify-qualifier (rest tree)))
+    (coll? tree) (simplify-qualifier (rest tree))
+    true tree))
+
+(defn simplify-second-of-two
+  "There are a number of possible simplifications such that if the `tree` has
+   only two elements, the second is semantically sufficient."
+  [tree]
+  (if (= (count tree) 2) (simplify (nth tree 1)) tree))
+
+
+(defn rule?
+  "Return true if the argument appears to be a parsed rule tree, else false."
+  [maybe-rule]
+  (and (coll? maybe-rule) (= (first maybe-rule) :RULE)))
+
+(defn simplify
+  "Simplify/canonicalise this `tree`. Opportunistically replace complex fragments with
+  semantically identical simpler fragments"
+  [tree]
+  (if
+    (coll? tree)
+    (case (first tree)
+      :ACTION (simplify-second-of-two tree)
+      :ACTIONS (simplify-second-of-two tree)
+      :COMPARATIVE (simplify-second-of-two tree)
+      :CONDITION (simplify-second-of-two tree)
+      :CONDITIONS (simplify-second-of-two tree)
+      :EXPRESSION (simplify-second-of-two tree)
+;;      :QUANTIFIER (simplify-second-of-two tree)
+      :NOT nil
+      :PROPERTY (simplify-second-of-two tree)
+      :SPACE nil
+      :THEN nil
+      ;; :QUALIFIER (simplify-qualifier tree)
+      :VALUE (simplify-second-of-two tree)
+      (remove nil? (map simplify tree)))
+    tree))
+
+(def parse-rule
+  "Parse the argument, assumed to be a string in the correct syntax, and return a parse tree."
+  (insta/parser grammar))
+
+(defn explain-parse-error-reason
+  "Attempt to explain the reason for the parse error."
+  [reason]
+  (str "Expecting one of (" (apply str (map #(str (:expecting %) " ") (first reason))) ")"))
+
+(defn throw-parse-exception
+  "Construct a helpful error message from this `parser-error`, and throw an exception with that message."
+  [parser-error]
+  (assert (coll? parser-error) "Expected a paser error structure?")
+  (let
+    [
+      ;; the error structure is a list, such that each element is a list of two items, and
+      ;; the first element in each sublist is a keyword. Easier to work with it as a map
+     error-map (reduce (fn [map item](merge map {(first item)(rest item)})) {} parser-error)
+     text (first (:text error-map))
+     reason (explain-parse-error-reason (:reason error-map))
+      ;; rules have only one line, by definition; we're interested in the column
+     column (if (:column error-map)(first (:column error-map)) 0)
+      ;; create a cursor to point to that column
+     cursor (apply str (reverse (conj (repeat column " ") "^")))
+     message (format bad-parse-error text cursor reason)
+     ]
+  (throw (Exception. message))))
+
+(defn compile-rule
+  "Compile this `rule`, assumed to be a string with appropriate syntax, into a function of two arguments,
+  a `cell` and a `world`, having the same semantics."
+  [rule]
+  (assert (string? rule))
+  (let [tree (simplify (parse-rule rule))]
+    (if (rule? tree) (eval (generate tree))
+      (throw-parse-exception tree))))
+
+