Added normalization tests for negations.

These tests ensure that multiple negations are eliminated, negated
quantifiers are replaced appropriately, negations introduced by
reduction are correctly handled, and negated disjunctions and
conjunctions are replaced according to De Morgan’s rules.

tests/data/normalization/normalization-4.pddl

@@ -0,0 +1,80 @@
+; tests that negations are correctly normalized
+(define (domain test-normalization)
+	(:predicates
+		(test-predicate-0)
+		(test-predicate-1 ?x)
+		(test-predicate-2 ?x ?y))
+
+	; multiple negations
+	(:action test-action-1
+		:parameters
+			(?x)
+		:precondition
+			(not (not (not (not (not (not (test-predicate-1 ?x)))))))
+		:effect
+			(test-predicate-1 ?x))
+
+	; multiple negations
+	(:action test-action-2
+		:parameters
+			(?x)
+		:precondition
+			(not (not (not (not (not (test-predicate-1 ?x))))))
+		:effect
+			(test-predicate-1 ?x))
+
+	; negated “exists” statement
+	(:action test-action-3
+		:parameters
+			(?x)
+		:precondition
+			(not (exists
+				(?x ?y)
+				(not (not (test-predicate-2 ?x ?y)))))
+		:effect
+			(test-predicate-1 ?x))
+
+	; negated “forall” statement
+	(:action test-action-4
+		:parameters
+			(?x)
+		:precondition
+			(not (forall
+				(?x ?y)
+				(not (not (not (test-predicate-2 ?x ?y))))))
+		:effect
+			(test-predicate-1 ?x))
+
+	; negations introduced by reduction
+	(:action test-action-5
+		:parameters
+			(?x)
+		:precondition
+			(imply
+				(not (test-predicate-0))
+				(test-predicate-1 ?x))
+		:effect
+			(test-predicate-1 ?x))
+
+	; negated disjunction
+	(:action test-action-6
+		:parameters
+			(?x)
+		:precondition
+			(not (imply
+				(test-predicate-0)
+				(not (test-predicate-1 ?x))))
+		:effect
+			(test-predicate-1 ?x))
+
+	; negated conjunction
+	(:action test-action-7
+		:parameters
+			(?x)
+		:precondition
+			(not (and
+				(not (test-predicate-0))
+				(not (test-predicate-1 ?x))))
+		:effect
+			(test-predicate-1 ?x))
+)