Implemented Expression Evaluation/Parsing with Proper Error Handling
This commit is contained in:
Kim Wittenburg
@@ -2,184 +2,335 @@
|
||||
// MPElementParser.m
|
||||
// MathPad
|
||||
//
|
||||
// Created by Kim Wittenburg on 06.09.14.
|
||||
// Created by Kim Wittenburg on 10.09.14.
|
||||
// Copyright (c) 2014 Kim Wittenburg. All rights reserved.
|
||||
//
|
||||
|
||||
#import "MPElementParser.h"
|
||||
#import "NSRegularExpression+MPParsingAdditions.h"
|
||||
|
||||
#define MPMultiplicationSymbol @"*"
|
||||
|
||||
@interface MPElementParser ()
|
||||
|
||||
@property (nonatomic) NSString *input;
|
||||
@property (nonatomic) NSUInteger parsePosition;
|
||||
|
||||
- (void)setError:(MPParseError *)error;
|
||||
|
||||
- (BOOL)isAtEnd;
|
||||
|
||||
- (NSRange)parseVariableDefinition:(NSString *__autoreleasing *)variableName;
|
||||
|
||||
- (NSRange)parseWhitespaces;
|
||||
- (NSRange)parseMultiplicationSymbol;
|
||||
- (NSRange)parseOperators;
|
||||
- (NSUInteger)countOperatorsInRange:(NSRange)range
|
||||
multiplicator:(out NSDecimalNumber *__autoreleasing *)multiplicator;
|
||||
- (NSRange)parseNumber;
|
||||
- (NSDecimalNumber *)numberInRange:(NSRange)range;
|
||||
|
||||
@end
|
||||
|
||||
@implementation MPElementParser {
|
||||
NSScanner *scanner;
|
||||
MPParseError *__autoreleasing *outError;
|
||||
}
|
||||
|
||||
- (MPParsedElement *)parseElement:(NSString *)string error:(MPParseError *__autoreleasing *)error
|
||||
{
|
||||
// Setup the Scanner
|
||||
scanner = [[NSScanner alloc] initWithString:string];
|
||||
scanner.charactersToBeSkipped = [NSCharacterSet whitespaceAndNewlineCharacterSet];
|
||||
scanner.caseSensitive = YES;
|
||||
|
||||
MPParsedElement *parsedElement = [[MPParsedElement alloc] init];
|
||||
|
||||
// Scan the defined variable
|
||||
NSString *firstCharacters = nil;
|
||||
BOOL hasLettersInFront = [scanner scanCharactersFromSet:[NSCharacterSet letterCharacterSet]
|
||||
intoString:&firstCharacters];
|
||||
BOOL foundEquals = [scanner scanString:@"="
|
||||
intoString:NULL];
|
||||
|
||||
if (hasLettersInFront && firstCharacters.length == 1 && foundEquals) {
|
||||
// Found variable definition
|
||||
parsedElement.definedVariable = firstCharacters;
|
||||
parsedElement.afterVariableDefinitionIndex = scanner.scanLocation;
|
||||
} else {
|
||||
// No variable definition found, reset the scanner
|
||||
parsedElement.definedVariable = nil;
|
||||
scanner.scanLocation = 0;
|
||||
}
|
||||
|
||||
// Scan the Prefix
|
||||
BOOL startsWithAsterisk = [scanner scanString:@"*"
|
||||
intoString:NULL];
|
||||
BOOL productClosed;
|
||||
NSDecimalNumber *prefix = [self scanClosedProduct:&productClosed
|
||||
error:NULL];
|
||||
|
||||
// Simple Factor
|
||||
if (scanner.isAtEnd) {
|
||||
parsedElement.isFactor = YES;
|
||||
parsedElement.value = prefix == nil ? [NSDecimalNumber one] : prefix;
|
||||
parsedElement.prefixOperatorExplicit = startsWithAsterisk;
|
||||
parsedElement.suffixOperatorExplicit = !productClosed;
|
||||
parsedElement.suffixIndex = scanner.scanLocation;
|
||||
return parsedElement;
|
||||
} else if (!productClosed) {
|
||||
if (error) {
|
||||
*error = MPParseError(scanner.scanLocation, @"Missing Number");
|
||||
}
|
||||
return nil;
|
||||
}
|
||||
|
||||
parsedElement.prefixOperatorExplicit = startsWithAsterisk;
|
||||
parsedElement.prefixValueExplicit = YES;
|
||||
parsedElement.prefixMultiplicator = prefix;
|
||||
|
||||
parsedElement.suffixValueExplicit = YES;
|
||||
|
||||
// Scan Summands
|
||||
NSDecimalNumber *value = [NSDecimalNumber zero];
|
||||
NSDecimalNumber *currentSummand;
|
||||
while (!scanner.isAtEnd) {
|
||||
static BOOL useUserDefaults;
|
||||
|
||||
// Add every summand but the last one
|
||||
if (currentSummand != nil) {
|
||||
value = [value decimalNumberByAdding:currentSummand];
|
||||
}
|
||||
|
||||
// Find the operator (+ or -)
|
||||
NSString *operator;
|
||||
BOOL found = [scanner scanString:@"+"
|
||||
intoString:&operator];
|
||||
if (!found) {
|
||||
found = [scanner scanString:@"-"
|
||||
intoString:&operator];
|
||||
}
|
||||
if (!found && !scanner.isAtEnd) {
|
||||
// Two numbers separated by just a space
|
||||
if (error) {
|
||||
*error = MPParseError(scanner.scanLocation, @"Missing Operator");
|
||||
}
|
||||
#pragma mark Creation Methods
|
||||
|
||||
+ (void)initialize
|
||||
{
|
||||
useUserDefaults = YES;
|
||||
}
|
||||
|
||||
- (instancetype)init
|
||||
{
|
||||
self = [super init];
|
||||
if (self) {
|
||||
self.allowsImplicitMultiplications = NO;
|
||||
self.maximumOperatorChainLength = 2;
|
||||
self.maximumOperatorChainLengthInMultiplication = 1;
|
||||
}
|
||||
return self;
|
||||
}
|
||||
|
||||
#pragma mark Properties
|
||||
|
||||
+ (BOOL)isUsingDefaultValuesFromUserDefaults
|
||||
{
|
||||
return useUserDefaults;
|
||||
}
|
||||
|
||||
+ (void)setUsingDefaultValuesFromUserDefaults:(BOOL)flag
|
||||
{
|
||||
useUserDefaults = flag;
|
||||
}
|
||||
|
||||
#pragma mark Parsing Methods
|
||||
|
||||
- (BOOL)isAtEnd
|
||||
{
|
||||
return self.parsePosition >= self.input.length;
|
||||
}
|
||||
|
||||
- (void)setError:(MPParseError *)error
|
||||
{
|
||||
if (outError != NULL) {
|
||||
*outError = error;
|
||||
}
|
||||
}
|
||||
|
||||
- (NSArray *)parseElement:(NSString *)string
|
||||
previousProduct:(MPParsedProduct *)previousProduct
|
||||
nextFactor:(MPParsedFactor *)nextFactor
|
||||
error:(out MPParseError *__autoreleasing *)error
|
||||
{
|
||||
return [self parseElement:string
|
||||
previousProduct:previousProduct
|
||||
nextFactor:nextFactor
|
||||
definesVariable:NO
|
||||
definedVariable:NULL
|
||||
error:error];
|
||||
}
|
||||
|
||||
- (NSArray *)parseElement:(NSString *)string
|
||||
previousProduct:(MPParsedProduct *)previousProduct
|
||||
nextFactor:(MPParsedFactor *)nextFactor
|
||||
definesVariable:(BOOL)flag
|
||||
definedVariable:(NSString *__autoreleasing *)variableName
|
||||
error:(out MPParseError *__autoreleasing *)error
|
||||
{
|
||||
self.input = string;
|
||||
outError = error;
|
||||
self.parsePosition = 0;
|
||||
|
||||
NSString *definedVariable;
|
||||
NSRange variableDefinitionRange = [self parseVariableDefinition:&definedVariable];
|
||||
if (flag) {
|
||||
if (!definedVariable) {
|
||||
self.error = MPParseError(NSMakeRange(0, 0), @"Expected Variable Definition");
|
||||
return nil;
|
||||
} else if (!found) {
|
||||
// Reached end of string
|
||||
break;
|
||||
}
|
||||
|
||||
currentSummand = [self scanClosedProduct:&productClosed
|
||||
error:error];
|
||||
|
||||
// No number was found
|
||||
if (currentSummand == nil) {
|
||||
// The string ends wit + or -
|
||||
if (scanner.isAtEnd) {
|
||||
productClosed = NO;
|
||||
parsedElement.suffixValueExplicit = NO;
|
||||
NSInteger suffix = [operator isEqualToString:@"+"] ? 1 : -1;
|
||||
currentSummand = [[NSDecimalNumber alloc] initWithInteger:suffix];
|
||||
if (error) {
|
||||
*error = nil;
|
||||
}
|
||||
break;
|
||||
// Something else instead of a number
|
||||
} else {
|
||||
if (error) {
|
||||
*error = MPParseError(scanner.scanLocation, @"Expected Number");
|
||||
}
|
||||
return nil;
|
||||
}
|
||||
}
|
||||
|
||||
// Process the current summand
|
||||
if ([operator isEqualToString:@"-"]) {
|
||||
currentSummand = [currentSummand decimalNumberByMultiplyingBy:[[NSDecimalNumber alloc] initWithInteger:-1]];
|
||||
}
|
||||
|
||||
// The summand ends with a *
|
||||
if (!productClosed) {
|
||||
// The string ends with a *
|
||||
if (scanner.isAtEnd) {
|
||||
parsedElement.suffixValueExplicit = YES;
|
||||
break;
|
||||
// After a * followed something else than a number
|
||||
} else {
|
||||
if (error) {
|
||||
*error = MPParseError(scanner.scanLocation, @"Unexpected Symbol");
|
||||
}
|
||||
return nil;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
parsedElement.value = value;
|
||||
parsedElement.suffixOperatorExplicit = !productClosed;
|
||||
parsedElement.suffixMultiplicator = currentSummand;
|
||||
parsedElement.suffixIndex = scanner.scanLocation;
|
||||
|
||||
return parsedElement;
|
||||
}
|
||||
|
||||
- (NSDecimalNumber *)scanClosedProduct:(BOOL *)closed error:(MPParseError **)error
|
||||
{
|
||||
NSDecimal decimal;
|
||||
BOOL found = [scanner scanDecimal:&decimal];
|
||||
if (!found) {
|
||||
if (error != NULL) {
|
||||
*error = MPParseError(scanner.scanLocation, @"Unexpected Symbol");
|
||||
} else if (variableName) {
|
||||
*variableName = definedVariable;
|
||||
}
|
||||
} else if (definedVariable) {
|
||||
self.error = MPParseError(variableDefinitionRange, @"Unexpected Variable Definition");
|
||||
return nil;
|
||||
}
|
||||
NSDecimalNumber *product = [NSDecimalNumber decimalNumberWithDecimal:decimal];
|
||||
while (true) {
|
||||
found = [scanner scanString:@"*"
|
||||
intoString:NULL];
|
||||
if (found) {
|
||||
found = [scanner scanDecimal:&decimal];
|
||||
if (found) {
|
||||
product = [product decimalNumberByMultiplyingBy:[NSDecimalNumber decimalNumberWithDecimal:decimal]];
|
||||
} else {
|
||||
if (closed != NULL) {
|
||||
*closed = NO;
|
||||
|
||||
NSMutableArray *products = [[NSMutableArray alloc] init];
|
||||
MPParsedProduct *currentProduct = previousProduct;
|
||||
|
||||
while (![self isAtEnd]) {
|
||||
[self parseWhitespaces];
|
||||
|
||||
NSRange multiplicationSymbolRange = [self parseMultiplicationSymbol];
|
||||
BOOL hasMultiplicationSymbol = multiplicationSymbolRange.location != NSNotFound;
|
||||
|
||||
NSRange operatorsRange = [self parseOperators];
|
||||
BOOL hasOperators = operatorsRange.location != NSNotFound;
|
||||
|
||||
// NSRange functionRange = ...
|
||||
// BOOL hasFunction = functionRange.location != NSNotFound;
|
||||
|
||||
NSRange numberRange = [self parseNumber];
|
||||
BOOL hasNumber = numberRange.location != NSNotFound;
|
||||
|
||||
|
||||
NSDecimalNumber *operatorMultiplicator;
|
||||
NSUInteger operatorCount = [self countOperatorsInRange:operatorsRange
|
||||
multiplicator:&operatorMultiplicator];
|
||||
|
||||
if (!hasNumber) {
|
||||
if ([self isAtEnd] && nextFactor != nil) {
|
||||
if (hasMultiplicationSymbol) {
|
||||
if (operatorCount > self.maximumOperatorChainLengthInFunction) {
|
||||
self.error = MPParseError(operatorsRange, @"Too many operators in multiplication.");
|
||||
return nil;
|
||||
}
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:operatorMultiplicator]];
|
||||
} else if (hasOperators) {
|
||||
if (operatorCount > self.maximumOperatorChainLength) {
|
||||
self.error = MPParseError(operatorsRange, @"Too many operators.");
|
||||
return nil;
|
||||
}
|
||||
[products addObject:currentProduct];
|
||||
currentProduct = [[MPParsedProduct alloc] init];
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:[[NSDecimalNumber alloc] initWithUnsignedInteger:operatorCount]]];
|
||||
} else if (self.allowsImplicitMultiplications) {
|
||||
if (!currentProduct) {
|
||||
currentProduct = [[MPParsedProduct alloc] init];
|
||||
}
|
||||
} else {
|
||||
self.error = MPParseError(NSMakeRange(self.parsePosition, 0), @"Implicit Multiplication not allowed.");
|
||||
return nil;
|
||||
}
|
||||
return product;
|
||||
break;
|
||||
} else if ([self isAtEnd]) {
|
||||
self.error = MPParseError(NSMakeRange(self.parsePosition, 0), @"Unexpected End. Expected Number.");
|
||||
return nil;
|
||||
} else {
|
||||
self.error = MPParseError(NSMakeRange(self.parsePosition, 1), @"Unexpected Symbol. Expected Number.");
|
||||
return nil;
|
||||
}
|
||||
} else {
|
||||
break;
|
||||
NSDecimalNumber *number = [self numberInRange:numberRange];
|
||||
NSDecimalNumber *value = [operatorMultiplicator decimalNumberByMultiplyingBy:number];
|
||||
|
||||
if (hasMultiplicationSymbol) {
|
||||
if (currentProduct) {
|
||||
if (operatorCount > self.maximumOperatorChainLengthInMultiplication) {
|
||||
self.error = MPParseError(operatorsRange, @"Too many operators in multiplication.");
|
||||
return nil;
|
||||
}
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:value]];
|
||||
} else {
|
||||
self.error = MPParseError(multiplicationSymbolRange, @"Unexpected Symbol. Expected Number.");
|
||||
return nil;
|
||||
}
|
||||
} else if (hasOperators) {
|
||||
if (operatorCount > self.maximumOperatorChainLength) {
|
||||
self.error = MPParseError(operatorsRange, @"Too many operators.");
|
||||
return nil;
|
||||
}
|
||||
if (currentProduct) {
|
||||
[products addObject:currentProduct];
|
||||
}
|
||||
currentProduct = [[MPParsedProduct alloc] init];
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:value]];
|
||||
} else if (!currentProduct) {
|
||||
currentProduct = [[MPParsedProduct alloc] init];
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:value]];
|
||||
} else if (self.allowsImplicitMultiplications) {
|
||||
[currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:value]];
|
||||
} else {
|
||||
self.error = MPParseError(NSMakeRange(numberRange.location, 0), @"Implicit Multiplication not allowed.");
|
||||
return nil;
|
||||
}
|
||||
}
|
||||
}
|
||||
if (closed != NULL) {
|
||||
*closed = YES;
|
||||
if (nextFactor) {
|
||||
[currentProduct addFactor:nextFactor];
|
||||
}
|
||||
return product;
|
||||
[products addObject:currentProduct];
|
||||
return products;
|
||||
}
|
||||
|
||||
static NSRegularExpression *variableDefinitionRegex;
|
||||
- (NSRange)parseVariableDefinition:(NSString *__autoreleasing *)variableName
|
||||
{
|
||||
if (!variableDefinitionRegex) {
|
||||
variableDefinitionRegex = [NSRegularExpression regularExpressionWithPattern:@"\\A\\s*([A-Za-z])\\s*=\\s*"
|
||||
options:0
|
||||
error:NULL];
|
||||
}
|
||||
|
||||
NSTextCheckingResult *match = [variableDefinitionRegex firstMatchInString:self.input
|
||||
fromIndex:self.parsePosition];
|
||||
if (!match) {
|
||||
return NSMakeRange(NSNotFound, 0);
|
||||
}
|
||||
self.parsePosition = NSMaxRange(match.range);
|
||||
NSRange variableDefinitionRange = [match rangeAtIndex:1];
|
||||
*variableName = [self.input substringWithRange:variableDefinitionRange];
|
||||
return variableDefinitionRange;
|
||||
}
|
||||
|
||||
static NSRegularExpression *whitespaceRegex;
|
||||
- (NSRange)parseWhitespaces
|
||||
{
|
||||
if (!whitespaceRegex) {
|
||||
whitespaceRegex = [NSRegularExpression regularExpressionWithPattern:@"\\A\\s*"
|
||||
options:0
|
||||
error:NULL];
|
||||
}
|
||||
NSTextCheckingResult *match = [whitespaceRegex firstMatchInString:self.input
|
||||
fromIndex:self.parsePosition];
|
||||
if (match) {
|
||||
self.parsePosition = NSMaxRange(match.range);
|
||||
return match.range;
|
||||
} else {
|
||||
return NSMakeRange(NSNotFound, 0);
|
||||
}
|
||||
}
|
||||
|
||||
static NSRegularExpression *multiplicationSymbolRegex;
|
||||
- (NSRange)parseMultiplicationSymbol
|
||||
{
|
||||
if (!multiplicationSymbolRegex) {
|
||||
NSString *multiplicationSymbolString = [NSRegularExpression escapedPatternForString:MPMultiplicationSymbol];
|
||||
NSString *multiplicationSymbolRegexString = [NSString stringWithFormat:@"\\A\\s*(%@)\\s*", multiplicationSymbolString];
|
||||
multiplicationSymbolRegex = [NSRegularExpression regularExpressionWithPattern:multiplicationSymbolRegexString
|
||||
options:0
|
||||
error:NULL];
|
||||
}
|
||||
NSTextCheckingResult *match = [multiplicationSymbolRegex firstMatchInString:self.input
|
||||
fromIndex:self.parsePosition];
|
||||
if (!match) {
|
||||
return NSMakeRange(NSNotFound, 0);
|
||||
}
|
||||
self.parsePosition = NSMaxRange(match.range);
|
||||
return [match rangeAtIndex:1];
|
||||
}
|
||||
|
||||
static NSRegularExpression *operatorsRegex;
|
||||
- (NSRange)parseOperators
|
||||
{
|
||||
if (!operatorsRegex) {
|
||||
operatorsRegex = [NSRegularExpression regularExpressionWithPattern:@"\\A\\s*([+-](?:\\s*[+-])*)\\s*"
|
||||
options:0
|
||||
error:NULL];
|
||||
}
|
||||
NSTextCheckingResult *match = [operatorsRegex firstMatchInString:self.input
|
||||
fromIndex:self.parsePosition];
|
||||
if (match == nil) {
|
||||
return NSMakeRange(NSNotFound, 0);
|
||||
}
|
||||
self.parsePosition = NSMaxRange(match.range);
|
||||
return [match rangeAtIndex:1];
|
||||
}
|
||||
|
||||
- (NSUInteger)countOperatorsInRange:(NSRange)range
|
||||
multiplicator:(out NSDecimalNumber *__autoreleasing *)outMultiplicator
|
||||
{
|
||||
if (range.location == NSNotFound) {
|
||||
*outMultiplicator = [NSDecimalNumber one];
|
||||
return 0;
|
||||
}
|
||||
NSString *operatorsString = [self.input substringWithRange:range];
|
||||
NSString *operators = [[operatorsString componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] componentsJoinedByString:@""];
|
||||
NSInteger multiplicator = 1;
|
||||
for (NSUInteger characterIndex; characterIndex < operators.length; characterIndex++) {
|
||||
if ([[operators substringWithRange:NSMakeRange(characterIndex, 1)] isEqualToString:@"-"]) {
|
||||
multiplicator *= -1;
|
||||
}
|
||||
}
|
||||
*outMultiplicator = [[NSDecimalNumber alloc] initWithInteger:multiplicator];
|
||||
return operators.length;
|
||||
}
|
||||
|
||||
- (NSRange)parseNumber
|
||||
{
|
||||
NSString *decimalSeparatorRegexString = [NSRegularExpression escapedPatternForString:[[NSLocale currentLocale] objectForKey:NSLocaleDecimalSeparator]];
|
||||
NSString *numberRegexFormat = [NSString stringWithFormat:@"\\A\\s*((?:\\d+(?:%@\\d+)?)|(?:%@\\d+))\\s*", decimalSeparatorRegexString, decimalSeparatorRegexString];
|
||||
NSRegularExpression *numberRegex = [NSRegularExpression regularExpressionWithPattern:numberRegexFormat
|
||||
options:0
|
||||
error:NULL];
|
||||
NSTextCheckingResult *match = [numberRegex firstMatchInString:self.input
|
||||
fromIndex:self.parsePosition];
|
||||
if (!match) {
|
||||
return NSMakeRange(NSNotFound, 0);
|
||||
}
|
||||
self.parsePosition = NSMaxRange(match.range);
|
||||
return [match rangeAtIndex:1];
|
||||
}
|
||||
|
||||
- (NSDecimalNumber *)numberInRange:(NSRange)range
|
||||
{
|
||||
NSString *numberString = [self.input substringWithRange:range];
|
||||
return [NSDecimalNumber decimalNumberWithString:numberString];
|
||||
}
|
||||
|
||||
@end
|
||||
|
||||
Reference in New Issue
Block a user