Merge pull request #76 from gnustep/UnitsOfMeasure

Implement Units of measure changes into GNUstep

Headers/Foundation/Foundation.h

@@ -55,12 +55,15 @@
 #import	<Foundation/NSConnection.h>
 #import	<Foundation/NSData.h>
 #import	<Foundation/NSDateFormatter.h>
+#import <Foundation/NSDateInterval.h>
+#import <Foundation/NSDateIntervalFormatter.h>
 #import	<Foundation/NSDate.h>
 #import	<Foundation/NSDecimalNumber.h>
 #import	<Foundation/NSDictionary.h>
 #import	<Foundation/NSDistantObject.h>
 #import	<Foundation/NSDistributedLock.h>
 #import	<Foundation/NSDistributedNotificationCenter.h>
+#import	<Foundation/NSEnergyFormatter.h>
 #import	<Foundation/NSEnumerator.h>
 #import	<Foundation/NSError.h>
 #import	<Foundation/NSException.h>
@@ -86,9 +89,12 @@
 #import	<Foundation/NSKeyedArchiver.h>
 #import	<Foundation/NSKeyValueCoding.h>
 #import	<Foundation/NSKeyValueObserving.h>
+#import <Foundation/NSLengthFormatter.h>
 #import	<Foundation/NSLock.h>
 #import	<Foundation/NSLocale.h>
 #import	<Foundation/NSMapTable.h>
+#import <Foundation/NSMeasurement.h>
+#import <Foundation/NSMeasurementFormatter.h>
 #import <Foundation/NSMetadata.h>
 #import	<Foundation/NSMethodSignature.h>
 #import	<Foundation/NSNotification.h>
@@ -138,6 +144,7 @@
 #import	<Foundation/NSTimeZone.h>
 #import <Foundation/NSUbiquitousKeyValueStore.h>
 #import	<Foundation/NSUndoManager.h>
+#import <Foundation/NSUnit.h>
 #import	<Foundation/NSURLAuthenticationChallenge.h>
 #import	<Foundation/NSURLCache.h>
 #import	<Foundation/NSURLConnection.h>

Headers/Foundation/MISSING

@@ -20,9 +20,6 @@ NSAppleEventDescriptor.h
 NSAppleEventManager.h
 NSBackgroundActivityScheduler.h
 NSDateComponentsFormatter.h
-NSDateIntervalFormatter.h
-NSDateInterval.h
-NSEnergyFormatter.h
 NSExtensionContext.h
 NSExtensionItem.h
 NSExtensionRequestHandling.h
@@ -30,44 +27,10 @@ NSHFSFileTypes.h
 NSISO8601DateFormatter.h
 NSItemProvider.h
 NSItemProviderReadingWriting.h
-NSLengthFormatter.h
 NSLinguisticTagger.h
-NSMassFormatter.h
-NSMeasurementFormatter.h
-NSMeasurement.h
 NSMetadataAttributes.h
 NSObjectScripting.h
 NSOrthography.h
-NSUnit.h
-NSUserActivity.h
-NSXPCConnection.h
--------------------------------------------------------------
-Foundation:
-==
-FoundationLegacySwiftCompatibility.h
-NSAppleEventDescriptor.h
-NSAppleEventManager.h
-NSBackgroundActivityScheduler.h
-NSDateComponentsFormatter.h
-NSDateIntervalFormatter.h
-NSDateInterval.h
-NSEnergyFormatter.h
-NSExtensionContext.h
-NSExtensionItem.h
-NSExtensionRequestHandling.h
-NSHFSFileTypes.h
-NSISO8601DateFormatter.h
-NSItemProvider.h
-NSItemProviderReadingWriting.h
-NSLengthFormatter.h
-NSLinguisticTagger.h
-NSMassFormatter.h
-NSMeasurementFormatter.h
-NSMeasurement.h
-NSMetadataAttributes.h
-NSObjectScripting.h
-NSOrthography.h
-NSUnit.h
 NSUserActivity.h
 NSXPCConnection.h
 

Headers/Foundation/NSDateInterval.h

@@ -0,0 +1,84 @@
+/* Definition of class NSDateInterval
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory Casamento <greg.casamento@gmail.com>
+   Date: Wed Oct  9 16:24:13 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSDateInterval_h_GNUSTEP_BASE_INCLUDE
+#define _NSDateInterval_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSObject.h>
+#include <Foundation/NSDate.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_12, GS_API_LATEST)
+
+@interface NSDateInterval : NSObject <NSCoding, NSCopying>
+{
+  NSTimeInterval _duration;
+  NSDate *_startDate;
+}
+  
+// Init
+- (instancetype) init;
+
+- (instancetype) initWithStartDate: (NSDate *)startDate 
+                          duration: (NSTimeInterval)duration;
+
+- (instancetype) initWithStartDate: (NSDate *)startDate
+                           endDate: (NSDate *)endDate;
+
+// Access
+- (NSDate *) startDate;
+- (void) setStartDate: (NSDate *)startDate;
+
+- (NSDate *) endDate;
+- (void) setEndDate: (NSDate *)endDate;
+
+- (NSTimeInterval)duration;
+- (void) setDuration: (NSTimeInterval)duration;
+
+// Compare
+- (NSComparisonResult) compare: (NSDateInterval *)dateInterval;
+
+- (BOOL) isEqualToDateInterval: (NSDateInterval *)dateInterval;
+
+// Determine
+- (BOOL) intersectsDateInterval: (NSDateInterval *)dateInterval;
+
+- (NSDateInterval *) intersectionWithDateInterval: (NSDateInterval *)dateInterval;
+
+// Contain
+- (BOOL) containsDate: (NSDate *)date;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSDateInterval_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSDateIntervalFormatter.h

@@ -0,0 +1,91 @@
+
+/* Definition of class NSDateIntervalFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Wed Oct  9 16:23:55 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSDateIntervalFormatter_h_GNUSTEP_BASE_INCLUDE
+#define _NSDateIntervalFormatter_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSFormatter.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_10, GS_API_LATEST)
+
+enum {
+  NSDateIntervalFormatterNoStyle = 0,
+  NSDateIntervalFormatterShortStyle = 1,
+  NSDateIntervalFormatterMediumStyle = 2,
+  NSDateIntervalFormatterLongStyle = 3,
+  NSDateIntervalFormatterFullStyle = 4
+};
+typedef NSUInteger NSDateIntervalFormatterStyle;
+
+@class NSCalendar, NSLocale, NSDateInterval;
+  
+@interface NSDateIntervalFormatter : NSFormatter
+{
+    NSLocale *_locale;
+    NSCalendar *_calendar;
+    NSTimeZone *_timeZone;
+    NSString *_dateTemplate;
+    NSDateIntervalFormatterStyle _dateStyle;
+    NSDateIntervalFormatterStyle _timeStyle;
+}
+
+// Properties
+- (NSLocale *) locale;
+- (void) setLocale: (NSLocale *)locale;
+
+- (NSCalendar *) calendar;
+- (void) setCalendar: (NSCalendar *)calendar;
+
+- (NSTimeZone *) timeZone;
+- (void) setTimeZone: (NSTimeZone *)timeZone;
+
+- (NSString *) dateTemplate;
+- (void) setDateTemplate: (NSString *)dateTemplate;
+
+- (NSDateIntervalFormatterStyle) dateStyle;
+- (void) setDateStyle: (NSDateIntervalFormatterStyle)dateStyle;
+  
+- (NSDateIntervalFormatterStyle) timeStyle;
+- (void) setTimeStyle: (NSDateIntervalFormatterStyle)timeStyle;
+
+// Create strings
+- (NSString *)stringFromDate:(NSDate *)fromDate toDate:(NSDate *)toDate;
+
+- (NSString *)stringFromDateInterval:(NSDateInterval *)dateInterval;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSDateIntervalFormatter_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSEnergyFormatter.h

@@ -0,0 +1,81 @@
+/* Definition of class NSEnergyFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Tue Oct  8 13:30:10 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSEnergyFormatter_h_GNUSTEP_BASE_INCLUDE
+#define _NSEnergyFormatter_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSFormatter.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_10, GS_API_LATEST)
+
+@class NSNumberFormatter, NSString;  
+  
+enum {
+    NSEnergyFormatterUnitJoule = 11,
+    NSEnergyFormatterUnitKilojoule = 14,
+    NSEnergyFormatterUnitCalorie = (7 << 8) + 1,       
+    NSEnergyFormatterUnitKilocalorie = (7 << 8) + 2,   
+};
+typedef NSInteger NSEnergyFormatterUnit;
+
+@interface NSEnergyFormatter : NSFormatter
+{
+  BOOL _isForFoodEnergyUse;
+  NSNumberFormatter *_numberFormatter;
+  NSFormattingUnitStyle _unitStyle;
+}
+
+- (NSNumberFormatter *) numberFormatter;
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter;
+  
+- (NSFormattingUnitStyle) unitStyle;
+- (void) setUnitStyle: (NSFormattingUnitStyle)style;
+  
+- (BOOL) isForFoodEnergyUse;
+- (void) setForFoodEnergyUse: (BOOL)flag;
+  
+- (NSString *) stringFromValue: (double)value unit: (NSEnergyFormatterUnit)unit;
+
+- (NSString *) stringFromJoules: (double)numberInJoules;
+
+- (NSString *) unitStringFromValue: (double)value unit: (NSEnergyFormatterUnit)unit;
+
+- (NSString *) unitStringFromJoules: (double)numberInJoules usedUnit: (NSEnergyFormatterUnit *)unitp;
+
+- (BOOL) getObjectValue:(id *)obj forString: (NSString *)string errorDescription: (NSString **)error;
+  
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSEnergyFormatter_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSLengthFormatter.h

@@ -0,0 +1,84 @@
+/* Definition of class NSLengthFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Tue Oct  8 13:30:33 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSLengthFormatter_h_GNUSTEP_BASE_INCLUDE
+#define _NSLengthFormatter_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSFormatter.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_10, GS_API_LATEST)
+enum {
+  NSLengthFormatterUnitMillimeter = 8,
+  NSLengthFormatterUnitCentimeter = 9,
+  NSLengthFormatterUnitMeter = 11,
+  NSLengthFormatterUnitKilometer = 14,
+  NSLengthFormatterUnitInch = (5 << 8) + 1,
+  NSLengthFormatterUnitFoot = (5 << 8) + 2,
+  NSLengthFormatterUnitYard = (5 << 8) + 3,
+  NSLengthFormatterUnitMile = (5 << 8) + 4,
+}; 
+typedef NSInteger NSLengthFormatterUnit;
+
+@class NSNumberFormatter, NSString;
+  
+@interface NSLengthFormatter : NSFormatter
+{
+  BOOL _isForPersonHeightUse;
+  NSNumberFormatter *_numberFormatter;
+  NSFormattingUnitStyle _unitStyle;
+}
+
+- (NSNumberFormatter *) numberFormatter;
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter;
+
+- (NSFormattingUnitStyle) unitStyle;
+- (void) setUnitStyle: (NSFormattingUnitStyle)style;
+  
+- (BOOL) isForPersonHeightUse;
+- (void) setForPersonHeightUse: (BOOL)flag;
+  
+- (NSString *) stringFromValue: (double)value unit: (NSLengthFormatterUnit)unit;
+
+- (NSString *) stringFromMeters: (double)numberInMeters;
+
+- (NSString *) unitStringFromValue: (double)value unit: (NSLengthFormatterUnit)unit;
+
+- (NSString *) unitStringFromMeters: (double)numberInMeters usedUnit: (NSLengthFormatterUnit *)unit;
+
+- (BOOL)getObjectValue: (id *)obj forString: (NSString *)string errorDescription: (NSString **)error;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSLengthFormatter_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSMassFormatter.h

@@ -0,0 +1,83 @@
+
+/* Definition of class NSMassFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSMassFormatter_h_GNUSTEP_BASE_INCLUDE
+#define _NSMassFormatter_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSFormatter.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_10, GS_API_LATEST)
+
+enum {
+    NSMassFormatterUnitGram = 11,
+    NSMassFormatterUnitKilogram = 14,
+    NSMassFormatterUnitOunce = (6 << 8) + 1,
+    NSMassFormatterUnitPound = (6 << 8) + 2,
+    NSMassFormatterUnitStone = (6 << 8) + 3,
+};  
+typedef NSInteger NSMassFormatterUnit;  
+
+@class NSNumberFormatter;
+  
+@interface NSMassFormatter : NSObject
+{
+  NSNumberFormatter *_numberFormatter;
+  BOOL _isForPersonMassUse;
+  NSFormattingUnitStyle _unitStyle;
+}
+
+- (NSNumberFormatter *) numberFormatter;
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter;
+  
+- (NSFormattingUnitStyle) unitStyle;
+- (void) setUnitStyle: (NSFormattingUnitStyle)style;
+
+- (BOOL) isForPersonMassUse;
+- (void) setForPersonMassUse: (BOOL)flag;
+  
+- (NSString *)stringFromValue: (double)value unit: (NSMassFormatterUnit)unit;
+
+- (NSString *)stringFromKilograms: (double)numberInKilograms;
+
+- (NSString *)unitStringFromValue: (double)value unit: (NSMassFormatterUnit)unit;
+
+- (NSString *)unitStringFromKilograms: (double)numberInKilograms usedUnit: (NSMassFormatterUnit *)unitp;
+
+- (BOOL)getObjectValue: (id*)obj forString: (NSString *)string errorDescription: (NSString **)error;
+  
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSMassFormatter_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSMeasurement.h

@@ -0,0 +1,74 @@
+/* Definition of class NSMeasurement
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSMeasurement_h_GNUSTEP_BASE_INCLUDE
+#define _NSMeasurement_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSObject.h>
+#include <Foundation/NSUnit.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_0, GS_API_LATEST)
+
+@class NSUnit;
+  
+@interface NSMeasurement : NSObject <NSCopying, NSCoding>
+{
+  NSUnit *_unit;
+  double _doubleValue;
+}
+  
+// Creating Measurements
+- (instancetype) initWithDoubleValue: (double)doubleValue 
+                                unit: (NSUnit *)unit;
+
+
+// Accessing unit and value
+- (NSUnit *) unit;
+
+- (double) doubleValue;
+
+// Conversion
+- (BOOL) canBeConvertedToUnit: (NSUnit *)unit;
+
+- (NSMeasurement *) measurementByConvertingToUnit: (NSUnit *)unit;
+
+// Operating
+- (NSMeasurement *) measurementByAddingMeasurement: (NSMeasurement *)measurement;
+
+- (NSMeasurement *) measurementBySubtractingMeasurement: (NSMeasurement *)measurement;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSMeasurement_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSMeasurementFormatter.h

@@ -0,0 +1,80 @@
+
+/* Definition of class NSMeasurementFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSMeasurementFormatter_h_GNUSTEP_BASE_INCLUDE
+#define _NSMeasurementFormatter_h_GNUSTEP_BASE_INCLUDE
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+  
+#include <Foundation/NSObject.h>
+#include <Foundation/NSFormatter.h>
+
+@class NSLocale, NSMeasurement, NSNumberFormatter, NSUnit;
+  
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_12, GS_API_LATEST)
+
+enum {
+    NSMeasurementFormatterUnitOptionsProvidedUnit = (1UL << 0),
+    NSMeasurementFormatterUnitOptionsNaturalScale = (1UL << 1),
+    NSMeasurementFormatterUnitOptionsTemperatureWithoutUnit = (1UL << 2),   
+};
+typedef NSUInteger NSMeasurementFormatterUnitOptions;
+  
+@interface NSMeasurementFormatter : NSFormatter <NSCoding>
+{
+  NSMeasurementFormatterUnitOptions _unitOptions;
+  NSFormattingUnitStyle _unitStyle;
+  NSLocale *_locale;
+  NSNumberFormatter *_numberFormatter;  
+}
+
+- (NSMeasurementFormatterUnitOptions) unitOptions;
+- (void) setUnitOptions: (NSMeasurementFormatterUnitOptions) unitOptions;
+  
+- (NSFormattingUnitStyle) unitStyle;
+- (void) setUnitStyle: (NSFormattingUnitStyle)style;
+
+- (NSLocale *) locale;
+- (void) setLocale: (NSLocale *)locale;
+
+- (NSNumberFormatter *) numberFormatter;
+- (void) setNumberFormatter: (NSNumberFormatter *)numberFormatter;  
+  
+- (NSString *)stringFromMeasurement: (NSMeasurement *)measurement;
+
+- (NSString *)stringFromUnit: (NSUnit *)unit;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSMeasurementFormatter_h_GNUSTEP_BASE_INCLUDE */
+

Headers/Foundation/NSUnit.h

@@ -0,0 +1,420 @@
+/* Definition of class NSUnit
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#ifndef _NSUnit_h_GNUSTEP_BASE_INCLUDE
+#define _NSUnit_h_GNUSTEP_BASE_INCLUDE
+
+#include <Foundation/NSObject.h>
+
+#if	defined(__cplusplus)
+extern "C" {
+#endif
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_12, GS_API_LATEST)
+
+// Unit converter
+@interface NSUnitConverter : NSObject
+- (double) baseUnitValueFromValue: (double)value;
+- (double) valueFromBaseUnitValue: (double)baseUnitValue;
+@end
+
+// Linea converter... for things like C <-> F conversion...
+@interface NSUnitConverterLinear : NSUnitConverter <NSCoding>
+{
+  double _coefficient;
+  double _constant;
+}
+- (instancetype) initWithCoefficient: (double)coefficient;
+- (instancetype) initWithCoefficient: (double)coefficient
+                            constant: (double)constant;
+- (double) coefficient;
+- (double) constant;
+@end
+
+// Units...  abstract...
+@interface NSUnit : NSObject <NSCopying, NSCoding>
+{
+  NSString *_symbol;
+}
+  
+- (instancetype) init;
+- (instancetype) initWithSymbol: (NSString *)symbol;
+- (NSString *) symbol;
+
+@end
+
+// Dimension using units....
+@interface NSDimension : NSUnit <NSCoding>
+{
+    double _value;
+    NSUnitConverter *_converter;
+}
+
+- (NSUnitConverter *) converter;
+- (instancetype) initWithSymbol: (NSString *)symbol converter: (NSUnitConverter *)converter ;
++ (instancetype) baseUnit;
+
+@end
+
+// Predefined....
+@interface NSUnitAcceleration : NSDimension 
+/*
+ Base unit - metersPerSecondSquared
+ */
+
++ (NSUnitAcceleration *) metersPerSecondSquared;
++ (NSUnitAcceleration *) gravity;
+
+@end
+
+@interface NSUnitAngle : NSDimension 
+/*
+ Base unit - degrees
+ */
+
++ (NSUnitAngle *) degrees;
++ (NSUnitAngle *) arcMinutes;
++ (NSUnitAngle *) arcSeconds;
++ (NSUnitAngle *) radians;
++ (NSUnitAngle *) gradians;
++ (NSUnitAngle *) revolutions;
+
+@end
+
+@interface NSUnitArea : NSDimension 
+/*
+ Base unit - squareMeters
+ */
+
++ (NSUnitArea *) squareMegameters;
++ (NSUnitArea *) squareKilometers;
++ (NSUnitArea *) squareMeters;
++ (NSUnitArea *) squareCentimeters;
++ (NSUnitArea *) squareMillimeters;
++ (NSUnitArea *) squareMicrometers;
++ (NSUnitArea *) squareNanometers;
++ (NSUnitArea *) squareInches;
++ (NSUnitArea *) squareFeet;
++ (NSUnitArea *) squareYards;
++ (NSUnitArea *) squareMiles;
++ (NSUnitArea *) acres;
++ (NSUnitArea *) ares;
++ (NSUnitArea *) hectares;
+
+@end
+
+@interface NSUnitConcentrationMass : NSDimension 
+/*
+ Base unit - gramsPerLiter
+ */
+
++ (NSUnitConcentrationMass *) gramsPerLiter;
++ (NSUnitConcentrationMass *) milligramsPerDeciliter;
+
++ (NSUnitConcentrationMass *) millimolesPerLiterWithGramsPerMole: (double)gramsPerMole;
+
+@end
+
+@interface NSUnitDispersion : NSDimension 
+/*
+ Base unit - partsPerMillion
+ */
++ (NSUnitDispersion *) partsPerMillion;
+
+@end
+
+@interface NSUnitDuration : NSDimension   
+/*
+ Base unit - seconds
+ */
+
++ (NSUnitDuration *) seconds;
++ (NSUnitDuration *) minutes;
++ (NSUnitDuration *) hours;
+
+@end
+
+@interface NSUnitElectricCharge : NSDimension 
+/*
+ Base unit - coulombs
+ */
+
++ (NSUnitElectricCharge *) coulombs;
++ (NSUnitElectricCharge *) megaampereHours;
++ (NSUnitElectricCharge *) kiloampereHours;
++ (NSUnitElectricCharge *) ampereHours;
++ (NSUnitElectricCharge *) milliampereHours;
++ (NSUnitElectricCharge *) microampereHours;
+
+@end
+
+@interface NSUnitElectricCurrent : NSDimension 
+/*
+ Base unit - amperes
+ */
+
++ (NSUnitElectricCurrent *) megaamperes;
++ (NSUnitElectricCurrent *) kiloamperes;
++ (NSUnitElectricCurrent *) amperes;
++ (NSUnitElectricCurrent *) milliamperes;
++ (NSUnitElectricCurrent *) microamperes;
+
+@end
+
+@interface NSUnitElectricPotentialDifference : NSDimension 
+/*
+ Base unit - volts
+ */
+
++ (NSUnitElectricPotentialDifference *) megavolts;
++ (NSUnitElectricPotentialDifference *) kilovolts;
++ (NSUnitElectricPotentialDifference *) volts;
++ (NSUnitElectricPotentialDifference *) millivolts;
++ (NSUnitElectricPotentialDifference *) microvolts;
+
+@end
+
+@interface NSUnitElectricResistance : NSDimension 
+/*
+ Base unit - ohms
+ */
+
++ (NSUnitElectricResistance *) megaohms;
++ (NSUnitElectricResistance *) kiloohms;
++ (NSUnitElectricResistance *) ohms;
++ (NSUnitElectricResistance *) milliohms;
++ (NSUnitElectricResistance *) microohms;
+
+@end
+
+@interface NSUnitEnergy : NSDimension 
+/*
+ Base unit - joules
+ */
+
++ (NSUnitEnergy *) kilojoules;
++ (NSUnitEnergy *) joules;
++ (NSUnitEnergy *) kilocalories;
++ (NSUnitEnergy *) calories;
++ (NSUnitEnergy *) kilowattHours;
+
+@end
+
+@interface NSUnitFrequency : NSDimension 
+/*
+ Base unit - hertz
+ */
+
++ (NSUnitFrequency *) terahertz;
++ (NSUnitFrequency *) gigahertz;
++ (NSUnitFrequency *) megahertz;
++ (NSUnitFrequency *) kilohertz;
++ (NSUnitFrequency *) hertz;
++ (NSUnitFrequency *) millihertz;
++ (NSUnitFrequency *) microhertz;
++ (NSUnitFrequency *) nanohertz;
+
+@end
+
+@interface NSUnitFuelEfficiency : NSDimension 
+/*
+ Base unit - litersPer100Kilometers
+ */
+
++ (NSUnitFuelEfficiency *) litersPer100Kilometers;
++ (NSUnitFuelEfficiency *) milesPerImperialGallon;
++ (NSUnitFuelEfficiency *) milesPerGallon;
+
+@end
+
+@interface NSUnitLength : NSDimension 
+/*
+ Base unit - meters
+ */
+
++ (NSUnitLength *) megameters;
++ (NSUnitLength *) kilometers;
++ (NSUnitLength *) hectometers;
++ (NSUnitLength *) decameters;
++ (NSUnitLength *) meters;
++ (NSUnitLength *) decimeters;
++ (NSUnitLength *) centimeters;
++ (NSUnitLength *) millimeters;
++ (NSUnitLength *) micrometers;
++ (NSUnitLength *) nanometers;
++ (NSUnitLength *) picometers;
++ (NSUnitLength *) inches;
++ (NSUnitLength *) feet;
++ (NSUnitLength *) yards;
++ (NSUnitLength *) miles;
++ (NSUnitLength *) scandinavianMiles;
++ (NSUnitLength *) lightyears;
++ (NSUnitLength *) nauticalMiles;
++ (NSUnitLength *) fathoms;
++ (NSUnitLength *) furlongs;
++ (NSUnitLength *) astronomicalUnits;
++ (NSUnitLength *) parsecs;
+
+@end
+
+@interface NSUnitIlluminance : NSDimension 
+/*
+ Base unit - lux
+ */
+
++ (NSUnitIlluminance *) lux;
+
+@end
+
+@interface NSUnitMass : NSDimension 
+/*
+ Base unit - kilograms
+ */
+
++ (NSUnitMass *) kilograms;
++ (NSUnitMass *) grams;
++ (NSUnitMass *) decigrams;
++ (NSUnitMass *) centigrams;
++ (NSUnitMass *) milligrams;
++ (NSUnitMass *) micrograms;
++ (NSUnitMass *) nanograms;
++ (NSUnitMass *) picograms;
++ (NSUnitMass *) ounces;
++ (NSUnitMass *) pounds;
++ (NSUnitMass *) stones;
++ (NSUnitMass *) metricTons;
++ (NSUnitMass *) shortTons;
++ (NSUnitMass *) carats;
++ (NSUnitMass *) ouncesTroy;
++ (NSUnitMass *) slugs;
+
+@end
+
+@interface NSUnitPower : NSDimension 
+/*
+ Base unit - watts
+ */
+
++ (NSUnitPower *) terawatts;
++ (NSUnitPower *) gigawatts;
++ (NSUnitPower *) megawatts;
++ (NSUnitPower *) kilowatts;
++ (NSUnitPower *) watts;
++ (NSUnitPower *) milliwatts;
++ (NSUnitPower *) microwatts;
++ (NSUnitPower *) nanowatts;
++ (NSUnitPower *) picowatts;
++ (NSUnitPower *) femtowatts;
++ (NSUnitPower *) horsepower;
+
+@end
+
+@interface NSUnitPressure : NSDimension 
+/*
+ Base unit - newtonsPerMetersSquared (equivalent to 1 pascal)
+ */
+
++ (NSUnitPressure *) newtonsPerMetersSquared;
++ (NSUnitPressure *) gigapascals;
++ (NSUnitPressure *) megapascals;
++ (NSUnitPressure *) kilopascals;
++ (NSUnitPressure *) hectopascals;
++ (NSUnitPressure *) inchesOfMercury;
++ (NSUnitPressure *) bars;
++ (NSUnitPressure *) millibars;
++ (NSUnitPressure *) millimetersOfMercury;
++ (NSUnitPressure *) poundsForcePerSquareInch;
+
+@end
+
+@interface NSUnitSpeed : NSDimension 
+/*
+ Base unit - metersPerSecond
+ */
+
++ (NSUnitSpeed *) metersPerSecond;
++ (NSUnitSpeed *) kilometersPerHour;
++ (NSUnitSpeed *) milesPerHour;
++ (NSUnitSpeed *) knots;
+
+@end
+
+@interface NSUnitTemperature : NSDimension 
+/*
+ Base unit - kelvin
+ */
++ (NSUnitTemperature *) kelvin;
++ (NSUnitTemperature *) celsius; 
++ (NSUnitTemperature *) fahrenheit;
+
+
+@end
+
+@interface NSUnitVolume : NSDimension 
+/*
+ Base unit - liters
+ */
+
++ (NSUnitVolume *) megaliters;
++ (NSUnitVolume *) kiloliters;
++ (NSUnitVolume *) liters;
++ (NSUnitVolume *) deciliters;
++ (NSUnitVolume *) centiliters;
++ (NSUnitVolume *) milliliters;
++ (NSUnitVolume *) cubicKilometers;
++ (NSUnitVolume *) cubicMeters;
++ (NSUnitVolume *) cubicDecimeters;
++ (NSUnitVolume *) cubicCentimeters;
++ (NSUnitVolume *) cubicMillimeters;
++ (NSUnitVolume *) cubicInches;
++ (NSUnitVolume *) cubicFeet;
++ (NSUnitVolume *) cubicYards;
++ (NSUnitVolume *) cubicMiles;
++ (NSUnitVolume *) acreFeet;
++ (NSUnitVolume *) bushels;
++ (NSUnitVolume *) teaspoons;
++ (NSUnitVolume *) tablespoons;
++ (NSUnitVolume *) fluidOunces;
++ (NSUnitVolume *) cups;
++ (NSUnitVolume *) pints;
++ (NSUnitVolume *) quarts;
++ (NSUnitVolume *) gallons;
++ (NSUnitVolume *) imperialTeaspoons;
++ (NSUnitVolume *) imperialTablespoons;
++ (NSUnitVolume *) imperialFluidOunces;
++ (NSUnitVolume *) imperialPints;
++ (NSUnitVolume *) imperialQuarts;
++ (NSUnitVolume *) imperialGallons;
++ (NSUnitVolume *) metricCups;
+
+@end
+
+#if	defined(__cplusplus)
+}
+#endif
+
+#endif	/* GS_API_MACOSX */
+
+#endif	/* _NSUnit_h_GNUSTEP_BASE_INCLUDE */
+

Source/GNUmakefile

@@ -213,6 +213,8 @@ NSConnection.m \
 NSData.m \
 NSDate.m \
 NSDateFormatter.m \
+NSDateInterval.m \
+NSDateIntervalFormatter.m \
 NSDebug.m \
 NSDecimal.m \
 NSDecimalNumber.m \
@@ -220,6 +222,7 @@ NSDictionary.m \
 NSDistantObject.m \
 NSDistributedLock.m \
 NSDistributedNotificationCenter.m \
+NSEnergyFormatter.m \
 NSEnumerator.m \
 NSError.m \
 NSException.m \
@@ -244,10 +247,14 @@ NSKeyedArchiver.m \
 NSKeyedUnarchiver.m \
 NSKeyValueCoding.m \
 NSKeyValueObserving.m \
+NSLengthFormatter.m \
 NSLocale.m \
 NSLock.m \
 NSLog.m \
 NSMapTable.m \
+NSMassFormatter.m \
+NSMeasurementFormatter.m \
+NSMeasurement.m \
 NSMetadata.m \
 NSMethodSignature.m \
 NSNotification.m \
@@ -292,6 +299,7 @@ NSScriptKeyValueCoding.m \
 NSScriptObjectSpecifiers.m \
 NSScriptStandardSuiteCommands.m \
 NSScriptSuiteRegistry.m \
+NSUnit.m \
 NSUserScriptTask.m \
 NSSerializer.m \
 NSSet.m \
@@ -401,6 +409,8 @@ NSCompoundPredicate.h \
 NSConnection.h \
 NSData.h \
 NSDateFormatter.h \
+NSDateInterval.h \
+NSDateIntervalFormatter.h \
 NSDate.h \
 NSDebug.h \
 NSDecimal.h \
@@ -409,6 +419,7 @@ NSDictionary.h \
 NSDistantObject.h \
 NSDistributedLock.h \
 NSDistributedNotificationCenter.h \
+NSEnergyFormatter.h \
 NSEnumerator.h \
 NSError.h \
 NSErrorRecoveryAttempting.h \
@@ -435,9 +446,13 @@ NSJSONSerialization.h \
 NSKeyedArchiver.h \
 NSKeyValueCoding.h \
 NSKeyValueObserving.h \
+NSLengthFormtter.h \
 NSLocale.h \
 NSLock.h \
 NSMapTable.h \
+NSMassFormatter.h \
+NSMeasurementFormatter.h \
+NSMeasurement.h \
 NSMetadata.h \
 NSMethodSignature.h \
 NSNetServices.h \
@@ -477,6 +492,7 @@ NSScriptKeyValueCoding.h \
 NSScriptObjectSpecifiers.h \
 NSScriptStandardSuiteCommands.h \
 NSScriptSuiteRegistry.h \
+NSUnit.h \
 NSUserScriptTask.h \
 NSScriptWhoseTests.h \
 NSSerialization.h \

Source/NSDateInterval.m

@@ -0,0 +1,221 @@
+/* Implementation of class NSDateInterval
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory Casamento <greg.casamento@gmail.com>
+   Date: Wed Oct  9 16:24:13 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSDateInterval.h>
+#include <Foundation/NSDate.h>
+#include <Foundation/NSArray.h>
+#include <Foundation/NSException.h>
+
+@implementation NSDateInterval
+
+// Init
+- (instancetype)init
+{
+  self = [super init];
+  if(self != nil)
+    {
+      _startDate = [NSDate date];
+      _duration = 0.0;
+      RETAIN(_startDate);
+    }
+  return self;
+}
+
+- (instancetype)initWithStartDate:(NSDate *)startDate 
+                         duration:(NSTimeInterval)duration
+{
+  self = [super init];
+  if(self != nil)
+    {
+      ASSIGNCOPY(_startDate, startDate);
+      if(duration < 0)
+        {
+          [NSException raise: NSInvalidArgumentException
+                      format: @"Duration %f is less than zero", duration];
+        }
+      _duration = duration;
+      
+    }
+  return self;
+}
+
+- (instancetype)initWithStartDate:(NSDate *)startDate 
+                          endDate:(NSDate *)endDate
+{
+  return [self initWithStartDate: startDate
+                        duration: [endDate timeIntervalSinceDate: startDate]];
+}
+
+- (instancetype) initWithCoder: (NSCoder *)coder
+{
+  // TODO: Implement encoding
+  return nil;
+}
+
+- (void) encodeWithCoder: (NSCoder *)coder
+{
+}
+
+- (id) copyWithZone: (NSZone *)zone
+{
+  return [[[self class] allocWithZone: zone]
+           initWithStartDate: _startDate
+                    duration: _duration];
+}
+
+- (void) dealloc
+{
+  RELEASE(_startDate);
+  [super dealloc];
+}
+
+// Access
+- (NSDate *) startDate
+{
+  return _startDate;
+}
+
+- (void) setStartDate: (NSDate *)startDate
+{
+  ASSIGNCOPY(_startDate, startDate);
+}
+
+- (NSDate *) endDate
+{
+  return [_startDate dateByAddingTimeInterval: _duration];
+}
+
+- (void) setEndDate: (NSDate *)endDate
+{
+  _duration = [endDate timeIntervalSinceDate: _startDate];
+}
+
+- (NSTimeInterval) duration
+{
+  return _duration;
+}
+
+- (void) setDuration: (NSTimeInterval)duration
+{
+  _duration = duration;
+}
+
+// Compare
+- (NSComparisonResult) compare: (NSDateInterval *)dateInterval
+{
+  NSComparisonResult result = NSOrderedSame;
+  
+  if([_startDate isEqualToDate: [dateInterval startDate]] &&
+     _duration < [dateInterval duration])
+    {
+      result = NSOrderedAscending;
+    }
+  else if([_startDate compare: [dateInterval startDate]] == NSOrderedAscending)
+    {
+      result = NSOrderedAscending;
+    }
+  else if([self isEqualToDateInterval: dateInterval])
+    {
+      result = NSOrderedSame;
+    }
+  else if([_startDate isEqualToDate: [dateInterval startDate]] &&
+          _duration > [dateInterval duration])
+    {
+      result = NSOrderedDescending;
+    }
+  else if([_startDate compare: [dateInterval startDate]] == NSOrderedDescending)
+    {
+      result = NSOrderedDescending;
+    }
+  
+  return result;
+}
+
+- (BOOL) isEqualToDateInterval: (NSDateInterval *)dateInterval
+{
+  return ([_startDate isEqualToDate: [dateInterval startDate]] &&
+          _duration == [dateInterval duration]);
+}
+
+// Determine
+- (BOOL) intersectsDateInterval: (NSDateInterval *)dateInterval
+{
+  return [self intersectionWithDateInterval: dateInterval] != nil;
+}
+
+- (NSDateInterval *) intersectionWithDateInterval: (NSDateInterval *)dateInterval
+{
+  NSDateInterval *result = nil;
+  NSDateInterval *first = self; //[sortedArray firstObject];
+  NSDateInterval *last = dateInterval; // [sortedArray lastObject];
+  NSDate *intersectStartDate = nil;
+  NSDate *intersectEndDate = nil;
+  // NSArray *array = [NSArray arrayWithObjects: self, dateInterval, nil];
+  // NSArray *sortedArray = [array sortedArrayUsingSelector: @selector(compare:)];
+
+  // Max of start date....
+  if([[first startDate] compare: [last startDate]] == NSOrderedAscending ||
+     [[first startDate] isEqualToDate: [last startDate]])
+    {
+      intersectStartDate = [last startDate];
+    }
+  if([[first startDate] compare: [last startDate]] == NSOrderedDescending)
+    {
+      intersectStartDate = [first startDate];
+    }
+
+  // Min of end date...
+  if([[first endDate] compare: [last endDate]] == NSOrderedDescending ||
+     [[first endDate] isEqualToDate: [last endDate]])
+    {
+      intersectEndDate = [last endDate];
+    }
+  if([[first endDate] compare: [last endDate]] == NSOrderedAscending)
+    {
+      intersectEndDate = [first endDate];
+    }
+
+  if([intersectStartDate compare: intersectEndDate] == NSOrderedAscending)
+    {
+      result = [[NSDateInterval alloc] initWithStartDate: intersectStartDate
+                                                 endDate: intersectEndDate];
+      AUTORELEASE(result);
+    }
+
+  return result;
+}
+
+// Contain
+- (BOOL) containsDate: (NSDate *)date
+{
+  NSDate *endDate = [self endDate];
+  return ([_startDate compare: date] == NSOrderedSame ||
+          [endDate compare: date] == NSOrderedSame ||
+          ([_startDate compare: date] == NSOrderedAscending &&
+           [endDate compare: date] == NSOrderedDescending));
+    
+}
+
+@end
+

Source/NSDateIntervalFormatter.m

@@ -0,0 +1,115 @@
+/* Implementation of class NSDateIntervalFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Wed Oct  9 16:23:55 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSDateIntervalFormatter.h>
+#include <Foundation/NSLocale.h>
+#include <Foundation/NSCalendar.h>
+#include <Foundation/NSTimeZone.h>
+#include <Foundation/NSString.h>
+#include <Foundation/NSDate.h>
+#include <Foundation/NSDateInterval.h>
+
+@implementation NSDateIntervalFormatter
+// Properties
+- (NSLocale *) locale
+{
+  return _locale;
+}
+
+- (void) setLocale: (NSLocale *)locale
+{
+  ASSIGNCOPY(_locale, locale);
+}
+
+- (NSCalendar *) calendar
+{
+  return _calendar;
+}
+
+- (void) setCalendar: (NSCalendar *)calendar
+{
+  ASSIGNCOPY(_calendar, calendar);
+}
+
+- (NSTimeZone *) timeZone
+{
+  return _timeZone;
+}
+
+- (void) setTimeZone: (NSTimeZone *)timeZone
+{
+  ASSIGNCOPY(_timeZone, timeZone);
+}
+
+- (NSString *) dateTemplate
+{
+  return _dateTemplate;
+}
+
+- (void) setDateTemplate: (NSString *)dateTemplate
+{
+  ASSIGNCOPY(_dateTemplate, dateTemplate);
+}
+
+- (NSDateIntervalFormatterStyle) dateStyle
+{
+  return _dateStyle;
+}
+
+- (void) setDateStyle: (NSDateIntervalFormatterStyle)dateStyle
+{
+  _dateStyle = dateStyle;
+}
+  
+- (NSDateIntervalFormatterStyle) timeStyle
+{
+  return _timeStyle;
+}
+
+- (void) setTimeStyle: (NSDateIntervalFormatterStyle)timeStyle
+{
+  _timeStyle = timeStyle;
+}
+
+// Create strings
+- (NSString *) stringFromDate: (NSDate *)fromDate toDate: (NSDate *)toDate
+{
+  NSDateInterval *interval = [[NSDateInterval alloc] initWithStartDate: fromDate
+                                                               endDate: toDate];
+  AUTORELEASE(interval);
+  return [self stringFromDateInterval: interval];
+}
+
+- (NSString *) stringFromDateInterval: (NSDateInterval *)dateInterval
+{
+  NSDate *fromDate = [dateInterval startDate];
+  NSDate *toDate = [dateInterval endDate];
+
+  // Add formatting of NSDate here.
+  
+  return [NSString stringWithFormat: @"%@ - %@", fromDate, toDate];
+}
+
+@end
+

Source/NSEnergyFormatter.m

@@ -0,0 +1,128 @@
+/* Implementation of class NSEnergyFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Tue Oct  8 13:30:10 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSEnergyFormatter.h>
+#include <Foundation/NSMeasurement.h>
+#include <Foundation/NSMeasurementFormatter.h>
+#include <Foundation/NSUnit.h>
+
+@implementation NSEnergyFormatter
+
+- (instancetype) init
+{
+  self = [super init];
+  if(self != nil)
+    {
+      _numberFormatter = nil;
+      _unitStyle = NSFormattingUnitStyleMedium;
+      _isForFoodEnergyUse = NO;
+    }
+  return self;
+}
+
+- (NSNumberFormatter *) numberFormatter
+{
+  return _numberFormatter;
+}
+
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter
+{
+  ASSIGN(_numberFormatter, formatter);
+}
+  
+- (NSFormattingUnitStyle) unitStyle
+{
+  return _unitStyle;
+}
+
+- (void) setUnitStyle: (NSFormattingUnitStyle)style
+{
+  _unitStyle = style;
+}
+  
+- (BOOL) isForFoodEnergyUse
+{
+  return _isForFoodEnergyUse;
+}
+
+- (void) setForFoodEnergyUse: (BOOL)flag
+{
+  _isForFoodEnergyUse = flag;
+}
+- (NSString *) stringFromValue: (double)value unit: (NSEnergyFormatterUnit)unit
+{
+  NSUnit *u = nil;
+  NSMeasurement *m = nil;
+  NSMeasurementFormatter *mf = nil;
+
+  switch(unit)
+    {
+    case NSEnergyFormatterUnitJoule:
+      u = [NSUnitEnergy joules];
+      break;
+    case NSEnergyFormatterUnitKilojoule:
+      u = [NSUnitEnergy kilojoules];
+      break;
+    case NSEnergyFormatterUnitCalorie:
+      u = [NSUnitEnergy calories];
+      break;
+    case NSEnergyFormatterUnitKilocalorie:
+      u = [NSUnitEnergy kilocalories];
+      break;
+    }
+
+  m = [[NSMeasurement alloc] initWithDoubleValue: value
+                                            unit: u];
+  AUTORELEASE(m);
+  mf = [[NSMeasurementFormatter alloc] init];
+  AUTORELEASE(mf);
+  [mf setUnitStyle: _unitStyle];
+  [mf setNumberFormatter: _numberFormatter];
+  
+  return [mf stringFromMeasurement: m];
+}
+
+- (NSString *) stringFromJoules: (double)numberInJoules
+{
+  return [self stringFromValue: numberInJoules unit: NSEnergyFormatterUnitJoule];
+}
+
+- (NSString *) unitStringFromValue: (double)value unit: (NSEnergyFormatterUnit)unit
+{
+  return [self stringFromValue: value unit: unit];
+}
+
+- (NSString *) unitStringFromJoules: (double)numberInJoules usedUnit: (NSEnergyFormatterUnit *)unit
+{
+  *unit = NSEnergyFormatterUnitJoule;
+  return [self stringFromValue: numberInJoules unit: *unit];
+}
+
+- (BOOL)getObjectValue: (id *)obj forString: (NSString *)string errorDescription: (NSString **)error
+{
+  return NO;
+}
+
+@end
+

Source/NSLengthFormatter.m

@@ -0,0 +1,148 @@
+
+/* Implementation of class NSLengthFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Tue Oct  8 13:30:33 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSLengthFormatter.h>
+#include <Foundation/NSUnit.h>
+#include <Foundation/NSMeasurement.h>
+#include <Foundation/NSMeasurementFormatter.h>
+
+@implementation NSLengthFormatter
+
+- (instancetype) init
+{
+  self = [super init];
+  if(self != nil)
+    {
+      _numberFormatter = nil;
+      _unitStyle = NSFormattingUnitStyleMedium;
+      _isForPersonHeightUse = NO;
+    }
+  return self;
+}
+
+- (void) dealloc
+{
+  RELEASE(_numberFormatter);
+  [super dealloc];
+}
+
+- (NSNumberFormatter *) numberFormatter
+{
+  return _numberFormatter;
+}
+
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter
+{
+  ASSIGN(_numberFormatter, formatter);
+}
+
+- (NSFormattingUnitStyle) unitStyle
+{
+  return _unitStyle;
+}
+
+- (void) setUnitStyle: (NSFormattingUnitStyle)style
+{
+  _unitStyle = style;
+}
+  
+- (BOOL) isForPersonHeightUse
+{
+  return _isForPersonHeightUse;
+}
+
+- (void) setForPersonHeightUse: (BOOL)flag
+{
+  _isForPersonHeightUse = flag;
+}
+  
+- (NSString *) stringFromValue: (double)value unit: (NSLengthFormatterUnit)unit
+{
+  NSUnit *u = nil;
+  NSMeasurement *m = nil;
+  NSMeasurementFormatter *mf = nil;
+
+  switch(unit)
+    {
+    case NSLengthFormatterUnitMillimeter:
+      u = [NSUnitLength millimeters];
+      break;
+    case NSLengthFormatterUnitCentimeter:
+      u = [NSUnitLength centimeters];
+      break;
+    case NSLengthFormatterUnitMeter:
+      u = [NSUnitLength meters];
+      break;
+    case NSLengthFormatterUnitKilometer:
+      u = [NSUnitLength kilometers];
+      break;
+    case NSLengthFormatterUnitInch:
+      u = [NSUnitLength inches];
+      break;
+    case NSLengthFormatterUnitFoot:
+      u = [NSUnitLength feet];
+      break;
+    case NSLengthFormatterUnitYard:
+      u = [NSUnitLength yards];
+      break;
+    case NSLengthFormatterUnitMile:
+      u = [NSUnitLength miles];
+      break;
+    }
+
+  m = [[NSMeasurement alloc] initWithDoubleValue: value
+                                            unit: u];
+  AUTORELEASE(m);
+  mf = [[NSMeasurementFormatter alloc] init];
+  AUTORELEASE(mf);
+  [mf setUnitStyle: _unitStyle];
+  [mf setNumberFormatter: _numberFormatter];
+  
+  return [mf stringFromMeasurement: m];
+}
+
+- (NSString *) stringFromMeters: (double)numberInMeters
+{
+  return [self stringFromValue: numberInMeters unit: NSLengthFormatterUnitMeter];
+}
+
+- (NSString *) unitStringFromValue: (double)value unit: (NSLengthFormatterUnit)unit
+{
+  return [self stringFromValue: value unit: unit];
+}
+
+- (NSString *) unitStringFromMeters: (double)numberInMeters usedUnit: (NSLengthFormatterUnit *)unit
+{
+  *unit = NSLengthFormatterUnitMeter;
+  return [self stringFromValue: numberInMeters unit: *unit];
+}
+
+- (BOOL)getObjectValue: (id *)obj forString: (NSString *)string errorDescription: (NSString **)error
+{
+  return NO;
+}
+
+@end
+

Source/NSMassFormatter.m

@@ -0,0 +1,133 @@
+
+/* Implementation of class NSMassFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: heron
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSMassFormatter.h>
+#include <Foundation/NSMeasurement.h>
+#include <Foundation/NSMeasurementFormatter.h>
+#include <Foundation/NSUnit.h>
+
+@implementation NSMassFormatter
+
+- (instancetype) init
+{
+  self = [super init];
+  if(self != nil)
+    {
+      _numberFormatter = nil;
+      _unitStyle = NSFormattingUnitStyleMedium;
+      _isForPersonMassUse = NO;
+    }
+  return self;
+}
+
+- (NSNumberFormatter *) numberFormatter
+{
+  return _numberFormatter;
+}
+
+- (void) setNumberFormatter: (NSNumberFormatter *)formatter
+{
+  ASSIGN(_numberFormatter, formatter);
+}
+  
+- (NSFormattingUnitStyle) unitStyle
+{
+  return _unitStyle;
+}
+
+- (void) setUnitStyle: (NSFormattingUnitStyle)style;
+{
+  _unitStyle = style;
+}
+
+- (BOOL) isForPersonMassUse;
+{
+  return _isForPersonMassUse;
+}
+
+- (void) setForPersonMassUse: (BOOL)flag;
+{
+  _isForPersonMassUse = flag;
+}
+
+- (NSString *)stringFromValue: (double)value unit: (NSMassFormatterUnit)unit;
+{
+  NSUnit *u = nil;
+  NSMeasurement *m = nil;
+  NSMeasurementFormatter *mf = nil;
+
+  switch(unit)
+    {
+    case NSMassFormatterUnitGram:
+      u = [NSUnitMass grams];
+      break;
+    case NSMassFormatterUnitKilogram:
+      u = [NSUnitMass kilograms];
+      break;
+    case NSMassFormatterUnitOunce:
+      u = [NSUnitMass ounces];
+      break;
+    case NSMassFormatterUnitPound:
+      u = [NSUnitMass pounds];
+      break;
+    case NSMassFormatterUnitStone:
+      u = [NSUnitMass stones];
+      break;
+    }
+
+  m = [[NSMeasurement alloc] initWithDoubleValue: value
+                                            unit: u];
+  AUTORELEASE(m);
+  mf = [[NSMeasurementFormatter alloc] init];
+  AUTORELEASE(mf);
+  [mf setUnitStyle: _unitStyle];
+  [mf setNumberFormatter: _numberFormatter];
+  
+  return [mf stringFromMeasurement: m];
+}
+
+- (NSString *)stringFromKilograms: (double)numberInKilograms;
+{
+  return [self stringFromValue: numberInKilograms unit: NSMassFormatterUnitKilogram];
+}
+
+- (NSString *)unitStringFromValue: (double)value unit: (NSMassFormatterUnit)unit;
+{
+  return [self stringFromValue: value unit: unit];
+}
+
+- (NSString *)unitStringFromKilograms: (double)numberInKilograms usedUnit: (NSMassFormatterUnit *)unit
+{
+  *unit = NSMassFormatterUnitKilogram;
+  return [self stringFromValue: numberInKilograms unit: *unit];
+}
+
+- (BOOL)getObjectValue: (id*)obj forString: (NSString *)string errorDescription: (NSString **)error
+{
+  return NO;
+}
+
+@end
+

Source/NSMeasurement.m

@@ -0,0 +1,157 @@
+/* Implementation of class NSMeasurement
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSMeasurement.h>
+#include <Foundation/NSUnit.h>
+#include <Foundation/NSException.h>
+#include <Foundation/NSArchiver.h>
+#include <Foundation/NSKeyedArchiver.h>
+
+@implementation NSMeasurement
+// Creating Measurements
+- (instancetype)initWithDoubleValue: (double)doubleValue 
+                               unit: (NSUnit *)unit
+{
+  self = [super init];
+  if(self != nil)
+    {
+      ASSIGNCOPY(_unit, unit);
+      _doubleValue = doubleValue;
+    }
+  return self;
+}
+
+- (void) dealloc
+{
+  RELEASE(_unit);
+  [super dealloc];
+}
+
+// Accessing unit and value
+- (NSUnit *) unit
+{
+  return _unit;
+}
+
+- (double) doubleValue
+{
+  return _doubleValue;
+}
+
+// Conversion
+- (BOOL) canBeConvertedToUnit: (NSUnit *)unit
+{
+  return ([unit isKindOfClass: [_unit class]] &&
+          [unit respondsToSelector: @selector(converter)]);
+}
+
+- (NSMeasurement *) measurementByConvertingToUnit: (NSUnit *)unit
+{
+  NSMeasurement *result = nil;
+  double val = 0.0;
+  if([self canBeConvertedToUnit: unit])
+    {
+      // Do conversion...
+      NSUnitConverter *c = [(NSDimension *)unit converter];
+      val = [c baseUnitValueFromValue: _doubleValue];
+      result = [[NSMeasurement alloc] initWithDoubleValue: val unit: unit];
+      AUTORELEASE(result);
+    }
+  else
+    {
+      [NSException raise: NSInvalidArgumentException
+                  format: @"Cannot convert from %@ to %@", _unit, unit];
+    }
+  return result;
+}
+
+// Operating
+- (NSMeasurement *) measurementByAddingMeasurement: (NSMeasurement *)measurement
+{
+  NSMeasurement *newMeasurement = [measurement measurementByConvertingToUnit: _unit];
+  NSMeasurement *result = nil;
+  double v = 0.0;
+
+  v = _doubleValue + [newMeasurement doubleValue];
+  result = [[NSMeasurement alloc] initWithDoubleValue: v unit: _unit];
+  AUTORELEASE(result);
+  
+  return result;
+}
+
+- (NSMeasurement *) measurementBySubtractingMeasurement: (NSMeasurement *)measurement
+{
+  NSMeasurement *newMeasurement = [measurement measurementByConvertingToUnit: _unit];
+  NSMeasurement *result = nil;
+  double v = 0.0;
+
+  v = _doubleValue - [newMeasurement doubleValue];
+  result = [[NSMeasurement alloc] initWithDoubleValue: v unit: _unit];
+  AUTORELEASE(result);
+  
+  return result;
+}
+
+// NSCopying
+- (id) copyWithZone: (NSZone *)zone
+{
+  return [[[self class] allocWithZone: zone] initWithDoubleValue: _doubleValue
+                                                            unit: _unit];
+}
+
+// NSCoding
+- (void) encodeWithCoder: (NSCoder *)coder
+{
+  if([coder allowsKeyedCoding])
+    {
+      // TODO: Verify that this is the correct encoding...
+      [coder encodeObject: _unit forKey: @"unit"];
+      [coder encodeDouble: _doubleValue forKey: @"doubleValue"];
+    }
+  else
+    {
+      [coder encodeObject: _unit];
+      [coder encodeValueOfObjCType: @encode(double) at: &_doubleValue];
+    }
+}
+
+- (id) initWithCoder: (NSCoder *)coder
+{
+  if((self = [super init]) != nil)
+    {
+      if([coder allowsKeyedCoding])
+        {
+          _unit = [coder decodeObjectForKey: @"unit"];
+          _doubleValue = [coder decodeDoubleForKey: @"doubleValue"];
+        }
+      else
+        {
+          _unit = [coder decodeObject];
+          [coder decodeValueOfObjCType: @encode(double) at: &_doubleValue];
+        }
+    }
+  return self;
+}
+@end
+

Source/NSMeasurementFormatter.m

@@ -0,0 +1,130 @@
+/* Implementation of class NSMeasurementFormatter
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   
+   By: Gregory John Casamento <greg.casamento@gmail.com>
+   Date: Mon Sep 30 15:58:21 EDT 2019
+
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02111 USA.
+*/
+
+#include <Foundation/NSMeasurementFormatter.h>
+#include <Foundation/NSLocale.h>
+#include <Foundation/NSMeasurement.h>
+#include <Foundation/NSNumberFormatter.h>
+#include <Foundation/NSUnit.h>
+
+@implementation NSMeasurementFormatter
+
+- (instancetype) init
+{
+  self = [super init];
+  if(self != nil)
+    {
+      _unitOptions = NSMeasurementFormatterUnitOptionsProvidedUnit;
+      _unitStyle = NSFormattingUnitStyleMedium;
+      _locale = RETAIN([NSLocale currentLocale]);
+    }
+  return self;
+}
+
+- (void) dealloc
+{
+  RELEASE(_locale);
+  [super dealloc];
+}
+
+- (NSMeasurementFormatterUnitOptions) unitOptions
+{
+  return _unitOptions;
+}
+
+- (void) setUnitOptions: (NSMeasurementFormatterUnitOptions) unitOptions
+{
+  _unitOptions = unitOptions;
+}
+  
+- (NSFormattingUnitStyle) unitStyle
+{
+  return _unitStyle;
+}
+
+- (void) setUnitStyle: (NSFormattingUnitStyle)style
+{
+  _unitStyle = style;
+}
+
+- (NSLocale *) locale
+{
+  return _locale;
+}
+
+- (void) setLocale: (NSLocale *)locale
+{
+  ASSIGNCOPY(_locale, locale);
+}
+
+- (NSNumberFormatter *) numberFormatter
+{
+  return _numberFormatter;
+}
+
+- (void) setNumberFormatter: (NSNumberFormatter *)numberFormatter
+{
+  ASSIGNCOPY(_numberFormatter, numberFormatter);
+}
+  
+- (NSString *)stringFromMeasurement: (NSMeasurement *)measurement
+{
+  NSString *result = nil;
+  NSNumber *num = [NSNumber numberWithDouble: [measurement doubleValue]];
+  NSUnit *u = [measurement unit];
+  
+  result = [_numberFormatter stringForObjectValue: num];
+  switch(_unitStyle)
+    {
+    case NSFormattingUnitStyleShort:
+    case NSFormattingUnitStyleMedium:
+    case NSFormattingUnitStyleLong:
+      result = [result stringByAppendingString: [self stringFromUnit: u]];
+      break;
+    }
+
+  return result;
+}
+
+- (NSString *)stringFromUnit: (NSUnit *)unit
+{
+  return [unit symbol];
+}
+
+- (NSString *)stringForObjectValue: (id)obj
+{
+  NSString *result = nil;
+  if([obj isKindOfClass: [NSMeasurement class]])
+    {
+      result = [self stringFromMeasurement: obj];
+    }
+  else if([obj isKindOfClass: [NSUnit class]])
+    {
+      result = [self stringFromUnit: obj];
+    }
+  return result;
+}
+
+@end
+