129 lines
4.1 KiB
Objective-C
129 lines
4.1 KiB
Objective-C
//
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// MPExpressionEvaluator.m
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// MathPad
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//
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// Created by Kim Wittenburg on 31.08.14.
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// Copyright (c) 2014 Kim Wittenburg. All rights reserved.
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//
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#import "MPExpressionEvaluator.h"
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#import "MPExpression.h"
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#import "MPFunction.h"
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@interface MPExpressionEvaluator ()
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@property (readwrite, nonatomic, strong) NSString *definedVariable;
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@end
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@implementation MPExpressionEvaluator {
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NSMutableDictionary *_variableBindings;
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MPElementParser *parser;
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}
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- (id)initWithExpression:(MPExpression *)expression
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{
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self = [super init];
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if (self) {
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_expression = expression;
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_variableBindings = [[NSMutableDictionary alloc] init];
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parser = [[MPElementParser alloc] init];
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}
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return self;
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}
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#pragma mark Evaluating Expressions
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- (NSDictionary *)variableBindings
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{
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return [_variableBindings copy];
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}
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- (void)bindValue:(NSDecimalNumber *)value toVariableName:(NSString *)name
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{
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[_variableBindings setObject:value
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forKey:name];
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}
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- (void)unbindVariableName:(NSString *)name
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{
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[_variableBindings removeObjectForKey:name];
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}
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- (NSDecimalNumber *)evaluateWithError:(MPParseError *__autoreleasing *)error
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{
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return [self evaluateVariableDefinition:NO error:error];
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}
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- (NSDecimalNumber *)evaluateVariableDefinition:(BOOL)flag error:(MPParseError *__autoreleasing *)error
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{
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// Empty Expression
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if (self.expression.numberOfElements == 0) {
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*error = MPParseError(NSMakeRange(0, 0), @"Expected Expression");
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return nil;
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}
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NSMutableArray *products = [[NSMutableArray alloc] init];
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MPParsedProduct *currentProduct = nil;
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for (NSUInteger elementIndex = 0; elementIndex < self.expression.numberOfElements; elementIndex++) {
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id<MPExpressionElement> element = [self.expression elementAtIndex:elementIndex];
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if ([element isString]) {
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MPParsedFactor *nextFactor = nil;
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if (elementIndex < self.expression.numberOfElements - 1) {
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MPFunction *nextFunction = (MPFunction *)[self.expression elementAtIndex:elementIndex+1];
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NSDecimalNumber *functionValue = [nextFunction evaluate:error];
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if (!functionValue) {
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return nil;
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}
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nextFactor = [MPParsedFactor factorWithDecimalNumber:functionValue];
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}
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NSArray *newProducts;
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if (elementIndex == 0 && flag) {
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NSString *definedVariable;
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newProducts = [parser parseElement:(NSString *)element
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previousProduct:currentProduct
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nextFactor:nextFactor
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definesVariable:YES
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definedVariable:&definedVariable
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error:error];
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self.definedVariable = definedVariable;
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} else {
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newProducts = [parser parseElement:(NSString *)element
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previousProduct:currentProduct
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nextFactor:nextFactor
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error:error];
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}
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if (!newProducts) {
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return nil;
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}
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for (NSUInteger productIndex = 0; productIndex < newProducts.count-1; productIndex++) {
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[products addObject:newProducts[productIndex]];
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}
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currentProduct = newProducts.lastObject;
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elementIndex++;
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} else {
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NSDecimalNumber *functionValue = [(MPFunction *)element evaluate:error];
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if (!functionValue) {
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return nil;
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}
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if (!currentProduct) {
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currentProduct = [[MPParsedProduct alloc] init];
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}
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[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:functionValue]];
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}
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}
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[products addObject:currentProduct];
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NSDecimalNumber *value = [NSDecimalNumber zero];
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for (MPParsedProduct *product in products) {
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value = [value decimalNumberByAdding:product.value];
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}
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return value;
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}
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@end
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