Implemented Evaluation

2014-09-07 16:45:31 +02:00
parent 8df8317413
commit 21bfe221ba
13 changed files with 593 additions and 96 deletions
--- a/MathPad/MPElementParser.m
+++ b/MathPad/MPElementParser.m
@@ -0,0 +1,185 @@
+//
+//  MPElementParser.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 06.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPElementParser.h"
+
+@implementation MPElementParser {
+    NSScanner *scanner;
+}
+
+- (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) {
+
+        // 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");
+            }
+            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");
+        }
+        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;
+                }
+                return product;
+            }
+        } else {
+            break;
+        }
+    }
+    if (closed != NULL) {
+        *closed = YES;
+    }
+    return product;
+}
+
+@end