Archive Project

Brainfuck/Lexer.m

@@ -0,0 +1,70 @@
+//
+//  Lexer.m
+//  Brainfuck
+//
+//  Created by Kim Wittenburg on 20.05.13.
+//  Copyright (c) 2013 brainfuck. All rights reserved.
+//
+
+#import "Lexer.h"
+
+@implementation Lexer {
+    NSString *script;
+    NSInteger pos;
+    NSInteger loopNestingLevel;
+    NSMutableArray *tokens;
+}
+
++ (Lexer *)lexer
+{
+    return [[self alloc] init];
+}
+
+- (id)init
+{
+    self = [super init];
+    if (self) {
+    }
+    return self;
+}
+
+- (NSArray *)performLexingOnString:(NSString *)s error:(NSError *__autoreleasing *)error
+{
+    pos = 0;
+    loopNestingLevel = -1;
+    script = s;
+    tokens = [[NSMutableArray alloc] init];
+    [self matchNextTokensInto:tokens error:error];
+    if (error) {
+        return nil;
+    }
+    return tokens;
+}
+
+- (void)matchNextTokensInto:(NSMutableArray *)target error:(NSError *__autoreleasing *)error;
+{
+    while (pos < script.length) {
+        int c = [script characterAtIndex:pos++];
+        NSString *character = [NSString stringWithFormat:@"%c", c];
+        if (c == '-' || c == '+' || c == '<' || c == '>' || c == '.' || c == ',') {
+            [target addObject:character];
+        } else if (c == '[') {
+            loopNestingLevel++;
+            NSMutableArray *subTokens = [NSMutableArray new];
+            [self matchNextTokensInto:subTokens error:error];
+            [target addObject:subTokens];
+        } else if (c == ']') {
+            if (loopNestingLevel-- == -1) {
+                NSError *err = [NSError errorWithDomain:@"Lexer" code:101 userInfo:@{NSLocalizedDescriptionKey: @"] without mathcing ["}];
+                *error = err;
+                return;
+            }
+            return;
+        }
+    }
+    if (loopNestingLevel >= 0) {
+        *error = [NSError errorWithDomain:@"Lexer" code:102 userInfo:@{NSLocalizedDescriptionKey: @"unclosed loop"}];
+    }
+}
+
+@end