Added cyclic state

Sources/E/State.swift

@@ -47,6 +47,7 @@ public extension StateResult {
 }
 
 public indirect enum State {
+    case cyclic(action: StateAction, to: State, while: () -> Bool)
     case some(with: StateResult)
     case transition(to: State, with: StateResult)
 }
@@ -54,6 +55,14 @@ public indirect enum State {
 public extension State {
     func run() {
         switch self {
+        case .cyclic(let action, let to, let statement):
+            guard statement() else {
+                return to.run()
+            }
+            
+            action.act()
+            run()
+            
         case .some(let action):
             action.resolve()
             

Tests/ETests/E_numTests.swift

@@ -72,8 +72,35 @@ final class ETests: XCTestCase {
         attemptRetryLogin.run()
     }
     
+    func testCyclicState() {
+        var value: Variable = .int(0)
+        let maxValue: Variable = .int(256)
+        let incValue: Function = .void {
+            value = value.update { .int($0 + 1) }
+        }
+        let boolFunc: Function = .out {
+            .bool(value.value() ?? 0 < maxValue.value() ?? 0)
+        }
+        
+        let finState = State.some(with: .some(action: .some(.void({
+            print("DONE!")
+            XCTAssert(true)
+        }))))
+        
+        let cyclicState = State.cyclic(action: .some(incValue), to: finState) {
+            boolFunc()?.value() ?? false
+        }
+        
+        XCTAssertEqual(value.value(), 0)
+
+        cyclicState.run()
+
+        XCTAssertEqual(value.value(), 256)
+    }
+    
     static var allTests = [
         ("testExample", testExample),
-        ("testState", testState)
+        ("testState", testState),
+        ("testCyclicState", testCyclicState)
     ]
 }