Started to Implement the Parser

MathPad/MPExpressionEvaluator.m

@@ -0,0 +1,56 @@
+//
+//  MPExpressionEvaluator.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 31.08.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPExpressionEvaluator.h"
+#import "MPExpression.h"
+
+#import "MPParsedElement.h"
+#import "MPMath.h"
+
+@implementation MPExpressionEvaluator {
+    NSMutableDictionary *_variableBindings;
+}
+- (id)initWithExpression:(MPExpression *)expression
+{
+    self = [super init];
+    if (self) {
+        _expression = expression;
+        _variableBindings = [[NSMutableDictionary alloc] init];
+    }
+    return self;
+}
+
+#pragma mark Lexing
+- (MPParsedElement *)structuredRepresentationOfElementAtIndex:(NSUInteger)index
+{
+    NSString *string = (NSString *)[self.expression elementAtIndex:index];
+    YY_BUFFER_STATE buffer = yy_scan_string(string.UTF8String);
+    yyparse();
+    yy_delete_buffer(buffer);
+    return [parseResult copy];
+}
+
+#pragma mark Evaluating Expressions
+- (NSDictionary *)variableBindings
+{
+    return [_variableBindings copy];
+}
+
+- (void)bindValue:(double)value toVariableName:(NSString *)name
+{
+    [_variableBindings setObject:@(value)
+                          forKey:name];
+}
+
+- (double)evaluateWithError:(NSError *__autoreleasing *)error
+{
+    MPParsedElement *element = [self structuredRepresentationOfElementAtIndex:0];
+    return element.standaloneValue;
+}
+
+@end