Merge pull request #11 from /issues/10-merge-kb

Issues/10 merge kb

Sources/LogicKit/KnowledgeBase.swift

@@ -95,10 +95,11 @@ public struct KnowledgeBase: Hashable {
 
   public static func + (lhs: KnowledgeBase, rhs: KnowledgeBase) -> KnowledgeBase {
     var result = KnowledgeBase(knowledge: [])
-    for (name, terms) in lhs.predicates {
-      result.predicates[name] = terms
+    for name in lhs.predicates.keys.concatenated(with: rhs.predicates.keys) {
+      result.predicates[name] = lhs.predicates[name] ?? []
       if let right = rhs.predicates[name] {
-        result.predicates[name]!.append(contentsOf: right)
+        let set = Set(result.predicates[name]!)
+        result.predicates[name]?.append(contentsOf: right.filter({ !set.contains($0) }))
       }
     }
     result.literals = lhs.literals.union(rhs.literals)

Tests/LogicKitTests/KnowledgeBaseTests.swift

@@ -0,0 +1,37 @@
+@testable import LogicKit
+import XCTest
+
+class KnowledgeBaseTests: XCTestCase {
+
+  func testMerge() {
+    let kb1: KnowledgeBase = [
+      .fact("foo", "bar"),
+      .rule("foo", .var("x")) {
+        .fact("foo", .var("x"))
+      },
+      .lit(12),
+      .lit(13),
+    ]
+
+    let kb2: KnowledgeBase = [
+      .fact("foo", "bar"),
+      .rule("foo", .var("y")) {
+        .fact("foo", .var("y"))
+      },
+      .lit(12),
+      .lit(14),
+    ]
+
+    let knowledge = Array(kb1 + kb2)
+    XCTAssert(knowledge.contains(.fact("foo", "bar")))
+    XCTAssert(knowledge.contains(.rule("foo", .var("x")) { .fact("foo", .var("x")) }))
+    XCTAssert(knowledge.contains(.rule("foo", .var("y")) { .fact("foo", .var("y")) }))
+    XCTAssert(knowledge.contains(.lit(12)))
+    XCTAssert(knowledge.contains(.lit(13)))
+    XCTAssert(knowledge.contains(.lit(14)))
+
+    XCTAssertEqual(knowledge.filter({ $0 == .fact("foo", "bar") }).count, 1)
+    XCTAssertEqual(knowledge.filter({ $0 == .lit(12) }).count, 1)
+  }
+
+}