diff --git a/DDMathParser.xcodeproj/project.pbxproj b/DDMathParser.xcodeproj/project.pbxproj
index 11b803d..24100e6 100644
--- a/DDMathParser.xcodeproj/project.pbxproj
+++ b/DDMathParser.xcodeproj/project.pbxproj
@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 46;
+	objectVersion = 51;
 	objects = {
 
 /* Begin PBXBuildFile section */
@@ -502,34 +502,33 @@
 			isa = PBXProject;
 			attributes = {
 				LastSwiftUpdateCheck = 0910;
-				LastUpgradeCheck = 0900;
+				LastUpgradeCheck = 1000;
 				TargetAttributes = {
 					55113C031FC35AC7001E508D = {
 						CreatedOnToolsVersion = 9.1;
-						DevelopmentTeam = 654LUM7646;
 						ProvisioningStyle = Automatic;
 					};
 					559B3EF81B74063600000108 = {
 						CreatedOnToolsVersion = 7.0;
-						DevelopmentTeam = 654LUM7646;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 1000;
+						ProvisioningStyle = Automatic;
 					};
 					559B3F011B74063600000108 = {
 						CreatedOnToolsVersion = 7.0;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 1000;
 					};
 				};
 			};
 			buildConfigurationList = 1DEB927808733DD40010E9CD /* Build configuration list for PBXProject "DDMathParser" */;
-			compatibilityVersion = "Xcode 3.2";
-			developmentRegion = English;
+			compatibilityVersion = "Xcode 10.0";
+			developmentRegion = en;
 			hasScannedForEncodings = 1;
 			knownRegions = (
-				English,
-				Japanese,
-				French,
-				German,
 				Base,
+				fr,
+				de,
+				ja,
+				en,
 			);
 			mainGroup = 08FB7794FE84155DC02AAC07 /* DDMathParser */;
 			projectDirPath = "";
@@ -690,12 +689,14 @@
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
 				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
 				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
@@ -728,8 +729,9 @@
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = macosx;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator watchsimulator watchos macosx appletvsimulator appletvos";
-				SWIFT_VERSION = 4.0;
-				VALID_ARCHS = "i386 x86_64 armv6 armv7 armv7s arm64";
+				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
+				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+				SWIFT_VERSION = 5.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				WATCHOS_DEPLOYMENT_TARGET = 2.0;
 			};
@@ -745,12 +747,14 @@
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
 				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
 				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
@@ -781,8 +785,8 @@
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				SDKROOT = macosx;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator watchsimulator watchos macosx appletvsimulator appletvos";
-				SWIFT_VERSION = 4.0;
-				VALID_ARCHS = "i386 x86_64 armv6 armv7 armv7s arm64";
+				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_VERSION = 5.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				WATCHOS_DEPLOYMENT_TARGET = 2.0;
 			};
@@ -814,14 +818,14 @@
 					"$(inherited)",
 				);
 				INFOPLIST_FILE = Demo/Info.plist;
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/../Frameworks",
+				);
 				MACOSX_DEPLOYMENT_TARGET = 10.13;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParser.Demo;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
-				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -846,13 +850,14 @@
 				DEVELOPMENT_TEAM = 654LUM7646;
 				GCC_C_LANGUAGE_STANDARD = gnu11;
 				INFOPLIST_FILE = Demo/Info.plist;
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/../Frameworks",
+				);
 				MACOSX_DEPLOYMENT_TARGET = 10.13;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParser.Demo;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
-				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -862,12 +867,13 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
-				CODE_SIGN_IDENTITY = "Mac Developer";
+				CODE_SIGN_IDENTITY = "";
+				CODE_SIGN_STYLE = Automatic;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEFINES_MODULE = YES;
-				DEVELOPMENT_TEAM = 654LUM7646;
+				DEVELOPMENT_TEAM = "";
 				DYLIB_COMPATIBILITY_VERSION = 1;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				GCC_PREPROCESSOR_DEFINITIONS = (
@@ -876,12 +882,16 @@
 				);
 				INFOPLIST_FILE = MathParser/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/Frameworks",
+				);
 				MTL_ENABLE_DEBUG_INFO = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParser;
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE_SPECIFIER = "";
 				SKIP_INSTALL = YES;
-				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 				TARGETED_DEVICE_FAMILY = "1,2,3,4";
 			};
 			name = Debug;
@@ -892,22 +902,27 @@
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
-				CODE_SIGN_IDENTITY = "Mac Developer";
+				CODE_SIGN_IDENTITY = "";
+				CODE_SIGN_STYLE = Automatic;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEFINES_MODULE = YES;
-				DEVELOPMENT_TEAM = 654LUM7646;
+				DEVELOPMENT_TEAM = "";
 				DYLIB_COMPATIBILITY_VERSION = 1;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				INFOPLIST_FILE = MathParser/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/Frameworks",
+				);
 				MTL_ENABLE_DEBUG_INFO = NO;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParser;
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE_SPECIFIER = "";
 				SKIP_INSTALL = YES;
-				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
 				TARGETED_DEVICE_FAMILY = "1,2,3,4";
 				VALIDATE_PRODUCT = YES;
 			};
@@ -927,14 +942,21 @@
 				);
 				INFOPLIST_FILE = MathParserTests/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
-				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "$(inherited) @executable_path/Frameworks @loader_path/../Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/Frameworks",
+				);
+				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/../Frameworks",
+				);
 				MTL_ENABLE_DEBUG_INFO = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParserTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos macosx watchos watchsimulator";
-				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 			};
 			name = Debug;
 		};
@@ -948,14 +970,21 @@
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				INFOPLIST_FILE = MathParserTests/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
-				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
-				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "$(inherited) @executable_path/Frameworks @loader_path/../Frameworks";
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/Frameworks",
+				);
+				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = (
+					"$(inherited)",
+					"@executable_path/Frameworks",
+					"@loader_path/../Frameworks",
+				);
 				MTL_ENABLE_DEBUG_INFO = NO;
 				PRODUCT_BUNDLE_IDENTIFIER = com.davedelong.MathParserTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos macosx watchos watchsimulator";
-				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
 				VALIDATE_PRODUCT = YES;
 			};
 			name = Release;
diff --git a/DDMathParser.xcodeproj/xcshareddata/xcschemes/MathParser.xcscheme b/DDMathParser.xcodeproj/xcshareddata/xcschemes/MathParser.xcscheme
index a8dd099..b6c9049 100644
--- a/DDMathParser.xcodeproj/xcshareddata/xcschemes/MathParser.xcscheme
+++ b/DDMathParser.xcodeproj/xcshareddata/xcschemes/MathParser.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0900"
+   LastUpgradeVersion = "1000"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
diff --git a/Demo/AnalyzerViewController.swift b/Demo/AnalyzerViewController.swift
index adc62d6..8988860 100644
--- a/Demo/AnalyzerViewController.swift
+++ b/Demo/AnalyzerViewController.swift
@@ -19,7 +19,7 @@ class AnalyzerViewController: NSViewController {
     weak var analyzerDelegate: AnalyzerDelegate?
     
     init() {
-        let nibName = NSNib.Name(rawValue: "\(type(of: self))")
+        let nibName = NSNib.Name("\(type(of: self))")
         let bundle = Bundle(for: type(of: self))
         super.init(nibName: nibName, bundle: bundle)
     }
diff --git a/Demo/DemoViewController.swift b/Demo/DemoViewController.swift
index cd36aca..2779e85 100644
--- a/Demo/DemoViewController.swift
+++ b/Demo/DemoViewController.swift
@@ -15,6 +15,8 @@ class DemoViewController: NSViewController, AnalyzerDelegate, NSTextFieldDelegat
     @IBOutlet var flowContainer: NSView?
     
     var flowController: AnalyzerFlowViewController?
+
+    private var controlChangeObserver: AnyObject?
     
     override func viewDidLoad() {
         super.viewDidLoad()
@@ -23,7 +25,7 @@ class DemoViewController: NSViewController, AnalyzerDelegate, NSTextFieldDelegat
 
         let flow = AnalyzerFlowViewController()
         flow.analyzerDelegate = self
-        addChildViewController(flow)
+        addChild(flow)
         
         flow.view.frame = container.bounds
         flow.view.autoresizingMask = [.width, .height]
@@ -32,11 +34,14 @@ class DemoViewController: NSViewController, AnalyzerDelegate, NSTextFieldDelegat
         
         flowController = flow
         flowController?.analyzeString("")
-    }
-    
-    override func controlTextDidChange(_ obj: Notification) {
-        let text = expressionField?.stringValue ?? ""
-        flowController?.analyzeString(text)
+
+        controlChangeObserver = NotificationCenter.default.addObserver(forName: NSControl.textDidChangeNotification,
+                                                                       object: expressionField,
+                                                                       queue: .main,
+                                                                       using: { [weak self] _ in
+                                                                        let text = self?.expressionField?.stringValue ?? ""
+                                                                        self?.flowController?.analyzeString(text)
+        })
     }
     
     func analyzerViewController(_ analyzer: AnalyzerViewController, wantsHighlightedRanges ranges: Array<Range<Int>>) {
diff --git a/MathParser/Expressionizer.swift b/MathParser/Expressionizer.swift
index 40b28d1..f8b2267 100644
--- a/MathParser/Expressionizer.swift
+++ b/MathParser/Expressionizer.swift
@@ -8,7 +8,7 @@
 
 import Foundation
 
-fileprivate extension GroupedToken {
+extension GroupedToken {
     fileprivate var groupedOperator: Operator? {
         guard case .operator(let o) = self.kind else { return nil }
         return o
diff --git a/MathParser/Functions+Defaults.swift b/MathParser/Functions+Defaults.swift
index 8e96da7..ba90ce3 100644
--- a/MathParser/Functions+Defaults.swift
+++ b/MathParser/Functions+Defaults.swift
@@ -8,7 +8,7 @@
 
 import Foundation
 
-public extension Function {
+extension Function {
     
     // MARK: - Angle mode helpers
     
@@ -837,6 +837,5 @@ public extension Function {
             return try state.evaluator.evaluate(state.arguments[2], substitutions: state.substitutions)
         }
     })
-    
 
 }
diff --git a/MathParser/Operator+Defaults.swift b/MathParser/Operator+Defaults.swift
index fd9ca37..b77dec6 100644
--- a/MathParser/Operator+Defaults.swift
+++ b/MathParser/Operator+Defaults.swift
@@ -44,7 +44,7 @@ public enum BuiltInOperator: String {
     case cubeRoot = "cuberoot"
 }
 
-public extension Operator {
+extension Operator {
     
     public static let defaultPowerAssociativity: Associativity = {
         
@@ -227,5 +227,5 @@ public extension Operator {
         self.init(builtInOperator: builtInOperator)
         self.precedence = precedence
     }
-    
+
 }
diff --git a/MathParser/OperatorSet.swift b/MathParser/OperatorSet.swift
index 10323d0..069d07c 100644
--- a/MathParser/OperatorSet.swift
+++ b/MathParser/OperatorSet.swift
@@ -156,7 +156,7 @@ public final class OperatorSet {
     private var knownTokens: Set<String>
     
     private func removeOperator(_ op: Operator) {
-        guard let index = operators.index(of: op) else { return }
+        guard let index = operators.firstIndex(of: op) else { return }
         operators.remove(at: index)
         operatorsDidChange()
     }
diff --git a/MathParser/ResolvedToken.swift b/MathParser/ResolvedToken.swift
index b949f68..70b2e11 100644
--- a/MathParser/ResolvedToken.swift
+++ b/MathParser/ResolvedToken.swift
@@ -21,7 +21,7 @@ public struct ResolvedToken {
     public let range: Range<Int>
 }
 
-public extension ResolvedToken.Kind {
+extension ResolvedToken.Kind {
     
     public var number: Double? {
         guard case .number(let o) = self else { return nil }
diff --git a/MathParser/String.swift b/MathParser/String.swift
index 0413e29..32252e6 100644
--- a/MathParser/String.swift
+++ b/MathParser/String.swift
@@ -8,11 +8,8 @@
 
 import Foundation
 
-public extension String {
-    
+extension String {
     public func evaluate(using evaluator: Evaluator = .default, _ substitutions: Substitutions = [:]) throws -> Double {
-        let e = try Expression(string: self)
-        return try evaluator.evaluate(e, substitutions: substitutions)
+        return try evaluator.evaluate(Expression(string: self), substitutions: substitutions)
     }
-    
 }