Implement GSCSConstraint and suppoorting classes

Source/GSCSVariable.h

@@ -1,19 +1,19 @@
 /* Copyright (C) 2023 Free Software Foundation, Inc.
-   
+
    By: Benjamin Johnson
    Date: 19-3-2023
    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 2.1 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
    Lesser 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,
@@ -25,7 +25,49 @@
 #ifndef _GS_CS_VARIABLE_H
 #define _GS_CS_VARIABLE_H
 
+enum GSCSVariableType
+{
+  GSCSVariableTypeDummy,
+  GSCSVariableTypeSlack,
+  GSCSVaraibleTypeVariable,
+  GSCSVariableTypeObjective,
+  GSCSVariableTypeExternal
+};
+typedef enum GSCSVariableType GSCSVariableType;
+
 @interface GSCSVariable : NSObject
+{
+  GSCSVariableType _type;
+  NSUInteger _id;
+  CGFloat _value;
+  NSString *_name;
+}
+
+- (GSCSVariableType) type;
+
+- (NSUInteger) id;
+
+- (CGFloat) value;
+
+- (void) setValue: (CGFloat)value;
+
+- (NSString *) name;
+
+- (BOOL) isExternal;
+
+- (BOOL) isDummy;
+
+- (BOOL) isPivotable;
+
+- (BOOL) isRestricted;
+
+- (instancetype) initWithName: (NSString *)name;
+
++ (instancetype) variable;
+
++ (instancetype) variableWithValue: (CGFloat)value;
+
++ (instancetype) variableWithValue: (CGFloat)value name: (NSString *)name;
 
 @end