Added the new declarative parser.
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src/cljs/mw3/parser.cljs
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358
src/cljs/mw3/parser.cljs
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(ns mw-parser.declarative
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(:use mw-engine.utils
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[clojure.string :only [split trim triml]])
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(:require [instaparse.core :as insta]))
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;; error thrown when an attempt is made to set a reserved property
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(def reserved-properties-error
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"The properties 'x' and 'y' of a cell are reserved and should not be set in rule actions")
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;; error thrown when a rule cannot be parsed. Slots are for
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;; (1) rule text
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;; (2) cursor showing where in the rule text the error occurred
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;; (3) the reason for the error
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(def bad-parse-error "I did not understand:\n'%s'\n%s\n%s")
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(def grammar
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;; in order to simplify translation into other natural languages, all
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;; TOKENS within the parser should be unambiguous
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"RULE := IF SPACE CONDITIONS SPACE THEN SPACE ACTIONS;
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CONDITIONS := DISJUNCT-CONDITION | CONJUNCT-CONDITION | PROPERTY-CONDITION | NEIGHBOURS-CONDITION ;
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DISJUNCT-CONDITION := CONDITION SPACE OR SPACE CONDITIONS;
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CONJUNCT-CONDITION := CONDITION SPACE AND SPACE CONDITIONS;
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CONDITION := NEIGHBOURS-CONDITION | PROPERTY-CONDITION;
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WITHIN-CONDITION := NEIGHBOURS-CONDITION SPACE WITHIN SPACE NUMERIC-EXPRESSION;
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NEIGHBOURS-CONDITION := WITHIN-CONDITION | QUANTIFIER SPACE NEIGHBOURS SPACE IS SPACE PROPERTY-CONDITION | QUANTIFIER SPACE NEIGHBOURS IS EXPRESSION | QUALIFIER SPACE NEIGHBOURS-CONDITION;
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PROPERTY-CONDITION := PROPERTY SPACE QUALIFIER SPACE EXPRESSION;
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EXPRESSION := SIMPLE-EXPRESSION | RANGE-EXPRESSION | NUMERIC-EXPRESSION | DISJUNCT-EXPRESSION | VALUE;
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SIMPLE-EXPRESSION := QUALIFIER SPACE EXPRESSION | VALUE;
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DISJUNCT-EXPRESSION := IN SPACE DISJUNCT-VALUE;
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RANGE-EXPRESSION := BETWEEN SPACE NUMERIC-EXPRESSION SPACE AND SPACE NUMERIC-EXPRESSION;
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NUMERIC-EXPRESSION := VALUE | VALUE SPACE OPERATOR SPACE NUMERIC-EXPRESSION;
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NEGATED-QUALIFIER := QUALIFIER SPACE NOT | NOT SPACE QUALIFIER;
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COMPARATIVE-QUALIFIER := IS SPACE COMPARATIVE SPACE THAN;
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QUALIFIER := COMPARATIVE-QUALIFIER | NEGATED-QUALIFIER | EQUIVALENCE | IS SPACE QUALIFIER;
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QUANTIFIER := NUMBER | SOME | NONE | ALL | COMPARATIVE SPACE THAN SPACE NUMBER;
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EQUIVALENCE := IS SPACE EQUAL | EQUAL | IS ;
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COMPARATIVE := MORE | LESS;
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DISJUNCT-VALUE := VALUE | VALUE SPACE OR SPACE DISJUNCT-VALUE;
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IF := 'if';
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THEN := 'then';
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THAN := 'than';
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OR := 'or';
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NOT := 'not';
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AND := 'and';
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SOME := 'some';
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NONE := 'no';
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ALL := 'all'
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BETWEEN := 'between';
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WITHIN := 'within';
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IN := 'in';
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MORE := 'more';
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LESS := 'less' | 'fewer';
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OPERATOR := '+' | '-' | '*' | '/';
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NEIGHBOURS := 'neighbour' | 'neighbor' | 'neighbours' | 'neighbors';
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PROPERTY := SYMBOL;
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VALUE := SYMBOL | NUMBER;
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EQUAL := 'equal to';
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IS := 'is' | 'are' | 'have' | 'has';
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NUMBER := #'[0-9]+' | #'[0-9]+.[0-9]+';
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SYMBOL := #'[a-z]+';
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ACTIONS := ACTION | ACTION SPACE 'and' SPACE ACTIONS
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ACTION := SIMPLE-ACTION | PROBABLE-ACTION;
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PROBABLE-ACTION := VALUE SPACE 'chance in' SPACE VALUE SPACE SIMPLE-ACTION;
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SIMPLE-ACTION := SYMBOL SPACE BECOMES SPACE EXPRESSION
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BECOMES := 'should be'
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SPACE := #' *'"
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)
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(defn TODO
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"Marker to indicate I'm not yet finished!"
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[message]
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message)
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(declare generate simplify)
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(defn suitable-fragment?
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"Return `true` if `tree-fragment` appears to be a tree fragment of the expected `type`."
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[tree-fragment type]
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(and (coll? tree-fragment)(= (first tree-fragment) type)))
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(defn assert-type
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"If `tree-fragment` is not a tree fragment of the expected `type`, throw an exception."
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[tree-fragment type]
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(assert (suitable-fragment? tree-fragment type)
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(throw (Exception. (format "Expected a %s fragment" type)))))
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(defn generate-rule
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"From this `tree`, assumed to be a syntactically correct rule specification,
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generate and return the appropriate rule as a function of two arguments."
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[tree]
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(assert-type tree :RULE)
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(list 'fn ['cell 'world] (list 'if (generate (nth tree 2)) (generate (nth tree 3)))))
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(defn generate-conditions
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"From this `tree`, assumed to be a syntactically correct conditions clause,
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generate and return the appropriate clojure fragment."
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[tree]
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(assert-type tree :CONDITIONS)
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(generate (nth tree 1)))
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(defn generate-condition
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[tree]
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(assert-type tree :CONDITION)
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(generate (nth tree 1)))
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(defn generate-conjunct-condition
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[tree]
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(assert-type tree :CONJUNCT-CONDITION)
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(list 'and (generate (nth tree 1))(generate (nth tree 3))))
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(defn generate-disjunct-condition
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[tree]
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(assert-type tree :DISJUNCT-CONDITION)
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(list 'or (generate (nth tree 1))(generate (nth tree 3))))
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(defn generate-ranged-property-condition
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"Generate a property condition where the expression is a numeric range"
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[tree property expression]
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(assert-type tree :PROPERTY-CONDITION)
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(assert-type (nth tree 3) :RANGE-EXPRESSION)
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(let [l1 (generate (nth expression 2))
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l2 (generate (nth expression 4))
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pv (list property 'cell)]
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(list 'let ['lower (list 'min l1 l2)
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'upper (list 'max l1 l2)]
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(list 'and (list '>= pv 'lower)(list '<= pv 'upper)))))
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(defn generate-disjunct-condition
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"Generate a property condition where the expression is a disjunct expression"
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[tree property qualifier expression]
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(let [e (list 'some (list 'fn ['i] '(= i value)) (list 'quote expression))]
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(list 'let ['value (list property 'cell)]
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(if (= qualifier '=) e
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(list 'not e)))))
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(defn generate-property-condition
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([tree]
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(assert-type tree :PROPERTY-CONDITION)
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(generate-property-condition tree (first (nth tree 3))))
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([tree expression-type]
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(assert-type tree :PROPERTY-CONDITION)
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(let [property (generate (nth tree 1))
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qualifier (generate (nth tree 2))
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expression (generate (nth tree 3))]
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(case expression-type
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:DISJUNCT-EXPRESSION (generate-disjunct-condition tree property qualifier expression)
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:RANGE-EXPRESSION (generate-ranged-property-condition tree property expression)
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(list qualifier (list property 'cell) expression)))))
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(defn generate-simple-action
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[tree]
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(assert-type tree :SIMPLE-ACTION)
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(let [property (generate (nth tree 1))
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expression (generate (nth tree 3))]
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(if (or (= property :x) (= property :y))
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(throw (Exception. reserved-properties-error))
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(list 'merge 'cell {property expression}))))
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(defn generate-multiple-actions
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[tree]
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nil)
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;; (assert (and (coll? tree)(= (first tree) :ACTIONS)) "Expected an ACTIONS fragment")
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;; (conj 'do (map
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(defn generate-disjunct-value
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"Generate a disjunct value. Essentially what we need here is to generate a
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flat list of values, since the `member` has already been taken care of."
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[tree]
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(assert-type tree :DISJUNCT-VALUE)
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(if (= (count tree) 4)
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(cons (generate (second tree)) (generate (nth tree 3)))
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(list (generate (second tree)))))
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(defn generate-numeric-expression
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[tree]
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(assert-type tree :NUMERIC-EXPRESSION)
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(case (first (second tree))
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:SYMBOL (list (keyword (second (second tree))) 'cell)
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(generate (second tree))))
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(defn generate-neighbours-condition
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"Generate code for a condition which refers to neighbours."
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([tree]
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(generate-neighbours-condition tree (first (second tree))))
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([tree quantifier-type]
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(let [quantifier (second (second tree))
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pc (generate (nth tree 4))]
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(case quantifier-type
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:NUMBER (generate-neighbours-condition '= (read-string quantifier) pc 1)
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:SOME (generate-neighbours-condition '> 0 pc 1)
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:QUANTIFIER
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(let [comparative (generate (simplify (second quantifier)))
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value (simplify (nth quantifier 5))]
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(generate-neighbours-condition comparative value pc 1)))))
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([comp1 quantity property-condition distance]
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(list comp1
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(list 'count (list 'remove false (list 'map (list 'fn ['cell] property-condition) '(get-neighbours cell world distance)))) quantity))
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([comp1 quantity property-condition]
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(generate-neighbours-condition comp1 quantity property-condition 1)))
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;; (def s1 "if 3 neighbours have state equal to forest then state should be forest")
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;; (def s2 "if some neighbours have state equal to forest then state should be forest")
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;; (def s3 "if more than 3 neighbours have state equal to forest then state should be forest")
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;; (def s4 "if fewer than 3 neighbours have state equal to forest then state should be forest")
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;; (def s5 "if all neighbours have state equal to forest then state should be forest")
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;; (def s6 "if more than 3 neighbours within 2 have state equal to forest then state should be forest")
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;; (nth (simplify (parse-rule s1)) 2)
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;; (second (nth (simplify (parse-rule s1)) 2))
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;; (nth (simplify (parse-rule s2)) 2)
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;; (map simplify (nth (simplify (parse-rule s2)) 2))
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;; ;; (second (nth (simplify (parse-rule s2)) 2))
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;; ;; (nth (simplify (parse-rule s3)) 2)
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;; (second (nth (simplify (parse-rule s3)) 2))
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;; (map simplify (second (nth (simplify (parse-rule s3)) 2)))
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;; ;; (nth (simplify (parse-rule s4)) 2)
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;; ;; (second (nth (simplify (parse-rule s4)) 2))
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;; ;; (nth (simplify (parse-rule s5)) 2)
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;; ;; (second (nth (simplify (parse-rule s5)) 2))
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;; ;; (nth (simplify (parse-rule s6)) 2)
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;; ;; (second (nth (simplify (parse-rule s6)) 2))
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;; ;; (generate (nth (nth (simplify (parse-rule s5)) 2) 4))
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;; ;; (generate (nth (simplify (parse-rule s2)) 2))
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;; ;; (generate (nth (simplify (parse-rule s1)) 2))
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;; (generate-neighbours-condition '= 3 '(= (:state cell) :forest) 1)
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;; (generate-neighbours-condition (nth (simplify (parse-rule s3)) 2))
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;; (generate-neighbours-condition (nth (simplify (parse-rule s2)) 2))
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;; (generate-neighbours-condition (nth (simplify (parse-rule s1)) 2))
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(defn generate
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"Generate code for this (fragment of a) parse tree"
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[tree]
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(if
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(coll? tree)
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(case (first tree)
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:ACTIONS (generate-multiple-actions tree)
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:COMPARATIVE (generate (second tree))
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:COMPARATIVE-QUALIFIER (generate (nth tree 2))
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:CONDITION (generate-condition tree)
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:CONDITIONS (generate-conditions tree)
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:CONJUNCT-CONDITION (generate-conjunct-condition tree)
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:DISJUNCT-CONDITION (generate-disjunct-condition tree)
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:DISJUNCT-EXPRESSION (generate (nth tree 2))
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:DISJUNCT-VALUE (generate-disjunct-value tree)
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:EQUIVALENCE '=
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:EXPRESSION (generate (second tree))
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:LESS '<
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:MORE '>
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:NEGATED-QUALIFIER (case (generate (second tree))
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= 'not=
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> '<
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< '>)
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:NEIGHBOURS-CONDITION (generate-neighbours-condition tree)
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:NUMERIC-EXPRESSION (generate-numeric-expression tree)
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:NUMBER (read-string (second tree))
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:PROPERTY (list (generate (second tree)) 'cell) ;; dubious - may not be right
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:PROPERTY-CONDITION (generate-property-condition tree)
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:QUALIFIER (generate (second tree))
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:RULE (generate-rule tree)
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:SIMPLE-ACTION (generate-simple-action tree)
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:SYMBOL (keyword (second tree))
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:VALUE (generate (second tree))
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(map generate tree))
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tree))
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(defn simplify-qualifier
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"Given that this `tree` fragment represents a qualifier, what
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qualifier is that?"
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[tree]
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(cond
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(empty? tree) nil
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(and (coll? tree)
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(member? (first tree) '(:EQUIVALENCE :COMPARATIVE))) tree
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(coll? (first tree)) (or (simplify-qualifier (first tree))
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(simplify-qualifier (rest tree)))
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(coll? tree) (simplify-qualifier (rest tree))
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true tree))
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(defn simplify-second-of-two
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"There are a number of possible simplifications such that if the `tree` has
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only two elements, the second is semantically sufficient."
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[tree]
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(if (= (count tree) 2) (simplify (nth tree 1)) tree))
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(defn rule?
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"Return true if the argument appears to be a parsed rule tree, else false."
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[maybe-rule]
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(and (coll? maybe-rule) (= (first maybe-rule) :RULE)))
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(defn simplify
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"Simplify/canonicalise this `tree`. Opportunistically replace complex fragments with
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semantically identical simpler fragments"
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[tree]
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(if
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(coll? tree)
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(case (first tree)
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:ACTION (simplify-second-of-two tree)
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:ACTIONS (simplify-second-of-two tree)
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:COMPARATIVE (simplify-second-of-two tree)
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:CONDITION (simplify-second-of-two tree)
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:CONDITIONS (simplify-second-of-two tree)
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:EXPRESSION (simplify-second-of-two tree)
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;; :QUANTIFIER (simplify-second-of-two tree)
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:NOT nil
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:PROPERTY (simplify-second-of-two tree)
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:SPACE nil
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:THEN nil
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;; :QUALIFIER (simplify-qualifier tree)
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:VALUE (simplify-second-of-two tree)
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(remove nil? (map simplify tree)))
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tree))
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(def parse-rule
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"Parse the argument, assumed to be a string in the correct syntax, and return a parse tree."
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(insta/parser grammar))
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(defn explain-parse-error-reason
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"Attempt to explain the reason for the parse error."
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[reason]
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(str "Expecting one of (" (apply str (map #(str (:expecting %) " ") (first reason))) ")"))
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(defn throw-parse-exception
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"Construct a helpful error message from this `parser-error`, and throw an exception with that message."
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[parser-error]
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(assert (coll? parser-error) "Expected a paser error structure?")
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(let
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[
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;; the error structure is a list, such that each element is a list of two items, and
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;; the first element in each sublist is a keyword. Easier to work with it as a map
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|
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))))
|
||||||
|
|
||||||
|
|
||||||
Loading…
Reference in a new issue