Redesign of the Evaluation System

MathPad/MPEvaluationContext.m

@@ -0,0 +1,63 @@
+//
+//  MPEvaluationContext.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 12.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPEvaluationContext.h"
+
+@interface MPEvaluationContext ()
+@property (nonatomic, strong) NSMutableArray *stack;
+@end
+
+@implementation MPEvaluationContext
+
+static MPEvaluationContext *sharedContext;
++ (MPEvaluationContext *)sharedContext
+{
+    if (!sharedContext) {
+        sharedContext = [[MPEvaluationContext alloc] init];
+    }
+    return sharedContext;
+}
+
+- (instancetype)init
+{
+    self = [super init];
+    if (self) {
+        _stack = [[NSMutableArray alloc] init];
+    }
+    return self;
+}
+
+- (void)push
+{
+    [self.stack addObject:[[NSMutableDictionary alloc] init]];
+}
+
+- (void)pop
+{
+    [self.stack removeLastObject];
+}
+
+- (void)bindValue:(NSDecimalNumber *)value toName:(NSString *)variableName
+{
+    NSMutableDictionary *currentBindings = self.stack.lastObject;
+    currentBindings[variableName] = value;
+}
+
+- (void)unbindVariableName:(NSString *)variableName
+{
+    NSMutableDictionary *currentBindings = self.stack.lastObject;
+    [currentBindings removeObjectForKey:variableName];
+}
+
+- (NSDecimalNumber *)valueForVariableName:(NSString *)variableName
+{
+    NSMutableDictionary *currentBindings = self.stack.lastObject;
+    return currentBindings[variableName];
+}
+
+@end