diff --git a/MathPad/MPExpression.h b/MathPad/MPExpression.h
index 7eb781d..28e3bd3 100644
--- a/MathPad/MPExpression.h
+++ b/MathPad/MPExpression.h
@@ -78,16 +78,21 @@ extern NSString *MPDivisionOperator;
 
 @interface MPMutableExpression : MPExpression
 
-- (void)replaceSymbolsInRange:(NSRange)range withSymbols:(NSArray *)symbols;
+- (void)replaceSymbolsInRange:(NSRange)range
+                  withSymbols:(NSArray *)symbols;
 
 @end
 
 @interface MPMutableExpression (MPMutableExpressionExtensionMethods)
 
-- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;
-- (void)insertFunction:(MPFunction *)aFunction atIndex:(NSUInteger)loc;
-- (void)insertExpression:(MPExpression *)anExpression atIndex:(NSUInteger)loc;
-- (void)insertSymbols:(NSArray *)symbols atIndex:(NSUInteger)loc;
+- (void)insertString:(NSString *)aString
+             atIndex:(NSUInteger)loc;
+- (void)insertFunction:(MPFunction *)aFunction
+               atIndex:(NSUInteger)loc;
+- (void)insertExpression:(MPExpression *)anExpression
+                 atIndex:(NSUInteger)loc;
+- (void)insertSymbols:(NSArray *)symbols
+              atIndex:(NSUInteger)loc;
 
 - (void)deleteSymbolsInRange:(NSRange)range;
 
diff --git a/MathPad/MPExpression.m b/MathPad/MPExpression.m
index 73d604e..bdcb62d 100644
--- a/MathPad/MPExpression.m
+++ b/MathPad/MPExpression.m
@@ -10,6 +10,8 @@
 #import "MPFunction.h"
 #import "MPException.h"
 
+#import "NSObject+MPStringTest.h"
+
 NSString *MPAdditionOperator = @"+";
 NSString *MPSubtractionOperator = @"-";
 NSString *MPMultiplicationOperator = @"*";
@@ -21,7 +23,9 @@ NSString *MPDivisionOperator = @"/";
 - (void)validateSymbols:(NSArray *)symbols;
 - (NSArray *)repairedSymbols:(NSArray *)symbols; // Merges subsequent strings
 - (void)repairSymbols:(NSMutableArray *)symbols;
-- (void)getSplitOffset:(out NSUInteger *)offset inSymbolAtIndex:(out NSUInteger *)symbolIndex forSplitLocation:(NSUInteger)loc;
+- (void)getSplitOffset:(out NSUInteger *)offset
+       inSymbolAtIndex:(out NSUInteger *)symbolIndex
+      forSplitLocation:(NSUInteger)loc;
 
 @end
 
@@ -98,7 +102,7 @@ NSString *MPDivisionOperator = @"/";
 
 - (NSInteger)lengthOfSymbol:(id)symbol
 {
-    if ([symbol isKindOfClass:[NSString class]]) {
+    if ([symbol isString]) {
         return [symbol length];
     }
     return 1;
@@ -108,7 +112,7 @@ NSString *MPDivisionOperator = @"/";
 - (void)validateSymbols:(NSArray *)symbols
 {
     for (id symbol in symbols) {
-        if (!([symbol isKindOfClass:[NSString class]]
+        if (!([symbol isString]
               || [symbol isKindOfClass:[MPFunction class]])) {
             @throw [NSException exceptionWithName:MPIllegalSymbolException
                                            reason:@"Only NSString and MPFunction objects are valid symbols."
@@ -127,19 +131,26 @@ NSString *MPDivisionOperator = @"/";
 
 - (void)repairSymbols:(NSMutableArray *)symbols
 {
-    for (NSInteger index = 1; index < symbols.count; index++) {
-        id last = symbols[index-1];
+    for (NSInteger index = 0; index < symbols.count; index++) {
+        id next = index+1 < symbols.count ? symbols[index+1] : nil;
         id current = symbols[index];
-        if ([last isKindOfClass:[NSString class]] && [current isKindOfClass:[NSString class]]) {
-            NSString *new = [NSString stringWithFormat:@"%@%@", last, current];
-            [symbols replaceObjectAtIndex:index-1 withObject:new];
-            [symbols removeObjectAtIndex:index];
-            index--;
+        if ([current isString]) {
+            if ([current length] == 0) {
+                [symbols removeObjectAtIndex:index];
+                index--;
+            } else if ([next isString]) {
+                NSString *new = [NSString stringWithFormat:@"%@%@", current, next];
+                [symbols replaceObjectAtIndex:index withObject:new];
+                [symbols removeObjectAtIndex:index+1];
+                index--;
+            }
         }
     }
 }
 
-- (void)getSplitOffset:(out NSUInteger *)offset inSymbolAtIndex:(out NSUInteger *)symbolIndex forSplitLocation:(NSUInteger)loc
+- (void)getSplitOffset:(out NSUInteger *)offset
+       inSymbolAtIndex:(out NSUInteger *)symbolIndex
+      forSplitLocation:(NSUInteger)loc
 {
     NSUInteger length = 0;
     NSUInteger index = 0;
@@ -227,7 +238,9 @@ NSString *MPDivisionOperator = @"/";
 - (MPExpression *)subexpressionWithRange:(NSRange)range
 {
     if (NSMaxRange(range) > self.length) {
-        @throw [NSException exceptionWithName:NSRangeException reason:@"Range outside bounds of expression." userInfo:nil];
+        @throw [NSException exceptionWithName:NSRangeException
+                                       reason:@"Range outside bounds of expression."
+                                     userInfo:nil];
     }
     if (range.location == self.length || NSMaxRange(range) == 0 || range.length == 0) {
         // Speed this up
@@ -235,20 +248,24 @@ NSString *MPDivisionOperator = @"/";
     }
     NSUInteger startOffset;
     NSUInteger startSymbolIndex;
-    [self getSplitOffset:&startOffset inSymbolAtIndex:&startSymbolIndex forSplitLocation:range.location];
+    [self getSplitOffset:&startOffset
+         inSymbolAtIndex:&startSymbolIndex
+        forSplitLocation:range.location];
     id startSymbol = _symbols[startSymbolIndex];
     if (startOffset == [self lengthOfSymbol:startSymbol]) {
         startOffset = 0;
         startSymbolIndex++;
         startSymbol = _symbols[startSymbolIndex];
-    } else if ([startSymbol isKindOfClass:[NSString class]]) {
+    } else if ([startSymbol isString]) {
         startSymbol = [startSymbol substringFromIndex:startOffset];
     }
     NSUInteger endOffset;
     NSUInteger endSymbolIndex;
-    [self getSplitOffset:&endOffset inSymbolAtIndex:&endSymbolIndex forSplitLocation:NSMaxRange(range)];
+    [self getSplitOffset:&endOffset
+         inSymbolAtIndex:&endSymbolIndex
+        forSplitLocation:NSMaxRange(range)];
     id endSymbol = _symbols[endSymbolIndex];
-    if ([endSymbol isKindOfClass:[NSString class]]) {
+    if ([endSymbol isString]) {
         endSymbol = [endSymbol substringToIndex:endOffset];
         
     }
@@ -261,9 +278,10 @@ NSString *MPDivisionOperator = @"/";
     }
     if (endSymbolIndex > startSymbolIndex) {
         [symbols addObject:endSymbol];
-    } else if (endSymbolIndex == startSymbolIndex && [startSymbol isKindOfClass:[NSString class]]) {
+    } else if (endSymbolIndex == startSymbolIndex && [startSymbol isString]) {
         NSString *result = [_symbols[startSymbolIndex] substringWithRange:NSMakeRange(startOffset, endOffset-startOffset)];
-        [symbols replaceObjectAtIndex:0 withObject:result];
+        [symbols replaceObjectAtIndex:0
+                           withObject:result];
     }
     return [[MPExpression alloc] initWithSymbols:symbols];
 }
@@ -343,13 +361,14 @@ NSString *MPDivisionOperator = @"/";
     NSMutableString *description = [[NSMutableString alloc] init];
     NSUInteger index = 0;
     for (id symbol in _symbols) {
-        if ([symbol isKindOfClass:[NSString class]]) {
+        if ([symbol isString]) {
             NSMutableString *correctedSymbol = [[symbol stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] mutableCopy];
             // Prefix operator
             if (symbol != _symbols[0]) {
                 unichar prefix = [correctedSymbol characterAtIndex:0];
                 if ([[NSCharacterSet decimalDigitCharacterSet] characterIsMember:prefix]) {
-                    [correctedSymbol insertString:@"*" atIndex:0];
+                    [correctedSymbol insertString:@"*"
+                                          atIndex:0];
                 }
             }
             // Suffix operator
@@ -385,7 +404,8 @@ NSString *MPDivisionOperator = @"/";
     self = [super initWithSymbols:nil];
     if (self) {
         symbols = [self repairedSymbols:symbols];
-        _symbols = [[NSMutableArray alloc] initWithArray:symbols copyItems:YES];
+        _symbols = [[NSMutableArray alloc] initWithArray:symbols
+                                               copyItems:YES];
     }
     return self;
 }
@@ -396,21 +416,26 @@ NSString *MPDivisionOperator = @"/";
     return [_symbols copy];
 }
 
-- (void)replaceSymbolsInRange:(NSRange)range withSymbols:(NSArray *)symbols
+- (void)replaceSymbolsInRange:(NSRange)range
+                  withSymbols:(NSArray *)symbols
 {
     if (NSMaxRange(range) > self.length) {
-        @throw [NSException exceptionWithName:NSRangeException reason:@"Range out of bounds of expression." userInfo:nil];
+        @throw [NSException exceptionWithName:NSRangeException
+                                       reason:@"Range out of bounds of expression."
+                                     userInfo:nil];
     }
     [self validateSymbols:symbols];
     
     // Locate the position, split the symbols
     NSUInteger startIndex;
-    [self splitSymbolsAtLocation:range.location insertionIndex:&startIndex];
+    [self splitSymbolsAtLocation:range.location
+                  insertionIndex:&startIndex];
     
     // Perform the deletion
     if (range.length > 0) {
         NSUInteger endIndex;
-        [self splitSymbolsAtLocation:NSMaxRange(range) insertionIndex:&endIndex];
+        [self splitSymbolsAtLocation:NSMaxRange(range)
+                      insertionIndex:&endIndex];
         NSMutableIndexSet *indexes = [[NSMutableIndexSet alloc] init];
         for (NSUInteger index = startIndex; index < endIndex; index++) {
             [indexes addIndex:index];
@@ -421,7 +446,8 @@ NSString *MPDivisionOperator = @"/";
     // Perform the insertion
     if (symbols.count > 0) {
         NSArray *newSymbols = [[NSArray alloc] initWithArray:symbols copyItems:YES];
-        [(NSMutableArray *)_symbols replaceObjectsInRange:NSMakeRange(startIndex, 0) withObjectsFromArray:newSymbols];
+        [(NSMutableArray *)_symbols replaceObjectsInRange:NSMakeRange(startIndex, 0)
+                                     withObjectsFromArray:newSymbols];
     }
     
     // Revalidate structure and invalidate length
@@ -429,11 +455,14 @@ NSString *MPDivisionOperator = @"/";
     _length = 0;
 }
 
-- (void)splitSymbolsAtLocation:(NSUInteger)loc insertionIndex:(out NSUInteger *)insertionIndex
+- (void)splitSymbolsAtLocation:(NSUInteger)loc
+                insertionIndex:(out NSUInteger *)insertionIndex
 {
     NSUInteger splitSymbolIndex;
     NSUInteger splitOffset;
-    [self getSplitOffset:&splitOffset inSymbolAtIndex:&splitSymbolIndex forSplitLocation:loc];
+    [self getSplitOffset:&splitOffset
+         inSymbolAtIndex:&splitSymbolIndex
+        forSplitLocation:loc];
     id splitSymbol = _symbols[splitSymbolIndex];
     NSInteger splitSymbolLength = [self lengthOfSymbol:splitSymbol];
     if (splitOffset == splitSymbolLength) {
@@ -443,9 +472,11 @@ NSString *MPDivisionOperator = @"/";
     if (splitOffset != 0) {
         NSString *leftPart = [splitSymbol substringToIndex:splitOffset];
         NSString *rightPart = [splitSymbol substringFromIndex:splitOffset];
-        [(NSMutableArray *)_symbols replaceObjectAtIndex:splitSymbolIndex withObject:leftPart];
+        [(NSMutableArray *)_symbols replaceObjectAtIndex:splitSymbolIndex
+                                              withObject:leftPart];
         splitSymbolIndex++;
-        [(NSMutableArray *)_symbols insertObject:rightPart atIndex:splitSymbolIndex];
+        [(NSMutableArray *)_symbols insertObject:rightPart
+                                         atIndex:splitSymbolIndex];
     }
     *insertionIndex = splitSymbolIndex;
 }
@@ -454,22 +485,29 @@ NSString *MPDivisionOperator = @"/";
 
 @implementation MPMutableExpression (MPMutableExpressionExtensionMethods)
 
-- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc
+- (void)insertString:(NSString *)aString
+             atIndex:(NSUInteger)loc
 {
-    [self insertSymbols:@[aString] atIndex:loc];
+    [self insertSymbols:@[aString]
+                atIndex:loc];
 }
 
-- (void)insertFunction:(MPFunction *)aFunction atIndex:(NSUInteger)loc
+- (void)insertFunction:(MPFunction *)aFunction
+               atIndex:(NSUInteger)loc
 {
-    [self insertSymbols:@[aFunction] atIndex:loc];
+    [self insertSymbols:@[aFunction]
+                atIndex:loc];
 }
 
-- (void)insertExpression:(MPExpression *)anExpression atIndex:(NSUInteger)loc
+- (void)insertExpression:(MPExpression *)anExpression
+                 atIndex:(NSUInteger)loc
 {
-    [self insertSymbols:anExpression.symbols atIndex:loc];
+    [self insertSymbols:anExpression.symbols
+                atIndex:loc];
 }
 
-- (void)insertSymbols:(NSArray *)symbols atIndex:(NSUInteger)loc
+- (void)insertSymbols:(NSArray *)symbols
+              atIndex:(NSUInteger)loc
 {
     [self replaceSymbolsInRange:NSMakeRange(loc, 0)
                     withSymbols:symbols];
diff --git a/MathPad/MPFunction.h b/MathPad/MPFunction.h
index 060814a..8e2bafa 100644
--- a/MathPad/MPFunction.h
+++ b/MathPad/MPFunction.h
@@ -18,7 +18,8 @@
 
 - (NSUInteger)numberOfChildren;
 - (MPExpression *)childAtIndex:(NSUInteger)index;
-- (void)setChild:(MPExpression *)child atIndex:(NSUInteger)index;
+- (void)setChild:(MPExpression *)child
+         atIndex:(NSUInteger)index;
 
 #pragma mark Evaluating Functions
 
diff --git a/MathPad/MPFunction.m b/MathPad/MPFunction.m
index 5424a0c..a1aa526 100644
--- a/MathPad/MPFunction.m
+++ b/MathPad/MPFunction.m
@@ -32,7 +32,8 @@
     return nil;
 }
 
-- (void)setChild:(MPExpression *)child atIndex:(NSUInteger)index
+- (void)setChild:(MPExpression *)child
+         atIndex:(NSUInteger)index
 {}
 
 #pragma mark Evaluating Functions