Fix bug with leading negation operator in roll commands

SA_DiceParser.m

 	{
 		NSString *operator = [dieRollString substringWithRange:lastOperatorRange];
 		
-		return [self legacyExpressionForStringDescribingOperation:dieRollString withOperator:operator atRange:lastOperatorRange];
+		// If the last (and thus only) operator is the leading character of
+		// the expression, then this is one of several possible special cases.
+		if(lastOperatorRange.location == 0)
+		{
+			NSMutableDictionary *expression;
+			
+			// First, we check for whether there even is anything more to the
+			// roll string besides the operator. If not, then the string is
+			// definitely malformed...
+			if(dieRollString.length == lastOperatorRange.length)
+			{
+				expression = [NSMutableDictionary dictionary];
+				expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
+				expression[SA_DB_INPUT_STRING] = dieRollString;
+				
+				addErrorToExpression(SA_DB_ERROR_INVALID_EXPRESSION, expression);
+				
+				return expression;
+			}
+			
+			// If the last operator is the leading character (i.e. there's just
+			// one operator in the expression, and it's at the beginning), and
+			// there's more to the expression than just the operator, then
+			// this is either an expression whose first term (which may or may
+			// not be its only term) is a simple value expression which
+			// represents a negative number - or, it's a malformed expression
+			// (because operators other than negation cannot begin an
+			// expression).
+			// In the former case, we do nothing, letting the testing for
+			// expression type fall through to the remaining cases (roll command
+			// or simple value).
+			// In the latter case, we register an error and return.
+			if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS] containsCharactersInString:operator])
+			{
+				// We've determined that this expression begins with a simple
+				// value expression that represents a negative number.
+				// This next line is a hack to account for the fact that Cocoa's
+				// Unicode compliance is incomplete. :( NSString's integerValue
+				// method only accepts the hyphen as a negation sign when reading a
+				// number - not any of the Unicode characters which officially
+				// symbolize negation! But we are more modern-minded, and accept
+				// arbitrary symbols as minus-sign. For proper parsing, though,
+				// we have to replace it like this...
+				dieRollString = [dieRollString stringByReplacingCharactersInRange:lastOperatorRange withString:@"-"];
+				
+				// Now we skip the remainder of the "is it an operator?" code
+				// and fall through to "is it a roll command, or maybe a simple
+				// value?"...
+			}
+			else
+			{
+				expression = [NSMutableDictionary dictionary];
+				expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
+				expression[SA_DB_INPUT_STRING] = dieRollString;
+				
+				addErrorToExpression(SA_DB_ERROR_INVALID_EXPRESSION, expression);
+				
+				return expression;
+			}
+		}
+		else
+		{
+			return [self legacyExpressionForStringDescribingOperation:dieRollString withOperator:operator atRange:lastOperatorRange];
+		}
 	}
 	
 	// If not an operation, the top-level term might be a die roll command.
 {
 	NSMutableDictionary *expression;
 	
-	// If the operator is at the beginning, this may be negation; we handle that
-	// case later below. Otherwise, it's a binary operator.
-	if(operatorRange.location != 0)
+	expression = [NSMutableDictionary dictionary];
+	expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
+	expression[SA_DB_INPUT_STRING] = dieRollString;
+	
+	// Operands of a binary operator are the expressions generated by 
+	// parsing the strings before and after the addition operator.
+	expression[SA_DB_OPERAND_LEFT] = [self legacyExpressionForLegalString:[dieRollString substringToIndex:operatorRange.location]];
+	expression[SA_DB_OPERAND_RIGHT] = [self legacyExpressionForLegalString:[dieRollString substringFromIndex:(operatorRange.location + operatorRange.length)]];
+	
+	// Check to see if the term is a subtraction operation.
+	if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS] containsCharactersInString:operator])
 	{
-		expression = [NSMutableDictionary dictionary];
-		expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
-		expression[SA_DB_INPUT_STRING] = dieRollString;
-		
-		// Operands of a binary operator are the expressions generated by 
-		// parsing the strings before and after the addition operator.
-		expression[SA_DB_OPERAND_LEFT] = [self legacyExpressionForLegalString:[dieRollString substringToIndex:operatorRange.location]];
-		expression[SA_DB_OPERAND_RIGHT] = [self legacyExpressionForLegalString:[dieRollString substringFromIndex:(operatorRange.location + operatorRange.length)]];
-		
-		// Check to see if the term is a subtraction operation.
-		if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS] containsCharactersInString:operator])
-		{
-			expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_MINUS;
-		}
-		// Check to see if the term is an addition operation.
-		else if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_PLUS] containsCharactersInString:operator])
-		{
-			expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_PLUS;
-		}
-		// Check to see if the term is a multiplication operation.
-		else if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_TIMES] containsCharactersInString:operator])
-		{
-			// Look for other, lower-precedence operators to the left of the 
-			// multiplication operator. If found, split the string there 
-			// instead of at the current operator.
-			NSString *allLowerPrecedenceOperators = [NSString stringWithFormat:@"%@%@", [SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_PLUS], [SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS]];
-			NSRange lastLowerPrecedenceOperatorRange = [dieRollString rangeOfCharacterFromSet:[NSCharacterSet characterSetWithCharactersInString:allLowerPrecedenceOperators] options:NSBackwardsSearch range:NSMakeRange(1, operatorRange.location - 1)];
-			if(lastLowerPrecedenceOperatorRange.location != NSNotFound)
-			{
-				NSString *lowerPrecedenceOperator = [dieRollString substringWithRange:lastLowerPrecedenceOperatorRange];
-				return [self legacyExpressionForStringDescribingOperation:dieRollString withOperator:lowerPrecedenceOperator atRange:lastLowerPrecedenceOperatorRange];
-			}
-			
-			expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_TIMES;
-		}
-		else
+		expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_MINUS;
+	}
+	// Check to see if the term is an addition operation.
+	else if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_PLUS] containsCharactersInString:operator])
+	{
+		expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_PLUS;
+	}
+	// Check to see if the term is a multiplication operation.
+	else if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_TIMES] containsCharactersInString:operator])
+	{
+		// Look for other, lower-precedence operators to the left of the 
+		// multiplication operator. If found, split the string there 
+		// instead of at the current operator.
+		NSString *allLowerPrecedenceOperators = [NSString stringWithFormat:@"%@%@", [SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_PLUS], [SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS]];
+		NSRange lastLowerPrecedenceOperatorRange = [dieRollString rangeOfCharacterFromSet:[NSCharacterSet characterSetWithCharactersInString:allLowerPrecedenceOperators] options:NSBackwardsSearch range:NSMakeRange(1, operatorRange.location - 1)];
+		if(lastLowerPrecedenceOperatorRange.location != NSNotFound)
 		{
-			addErrorToExpression(SA_DB_ERROR_UNKNOWN_OPERATOR, expression);
+			NSString *lowerPrecedenceOperator = [dieRollString substringWithRange:lastLowerPrecedenceOperatorRange];
+			return [self legacyExpressionForStringDescribingOperation:dieRollString withOperator:lowerPrecedenceOperator atRange:lastLowerPrecedenceOperatorRange];
 		}
+		
+		expression[SA_DB_OPERATOR] = SA_DB_OPERATOR_TIMES;
 	}
-	// Check to see if the term is a negation operation (we can only reach this
-	// case if the subtraction operator is at the beginning).
 	else
 	{
-		if(dieRollString.length == operatorRange.length)
-		{
-			expression = [NSMutableDictionary dictionary];
-			expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
-			expression[SA_DB_INPUT_STRING] = dieRollString;
-			
-			addErrorToExpression(SA_DB_ERROR_INVALID_EXPRESSION, expression);
-			
-			return expression;
-		}		
-		if([[SA_DiceParser validCharactersForOperator:SA_DB_OPERATOR_MINUS] containsCharactersInString:operator])
-		{
-			// It turns out this isn't actually an operation expression. It's a
-			// simple value expression with a negative number.
-			
-			// This next line is a hack to account for the fact that Cocoa's 
-			// Unicode compliance is incomplete. :( NSString's integerValue
-			// method only accepts the hyphen as a negation sign when reading a
-			// number - not any of the Unicode characters which officially
-			// symbolize negation! But we are more modern-minded, and accept 
-			// arbitrary symbols as minus-sign. For proper parsing, though, 
-			// we have to replace it like this...
-			NSString *fixedRollString = [dieRollString stringByReplacingCharactersInRange:operatorRange withString:@"-"];
-			
-			return [self legacyExpressionForStringDescribingNumericValue:fixedRollString];			
-		}
-		else
-		{
-			expression = [NSMutableDictionary dictionary];
-			expression[SA_DB_TERM_TYPE] = SA_DB_TERM_TYPE_OPERATION;
-			expression[SA_DB_INPUT_STRING] = dieRollString;
-			
-			addErrorToExpression(SA_DB_ERROR_INVALID_EXPRESSION, expression);
-			
-			return expression;
-		}
+		addErrorToExpression(SA_DB_ERROR_UNKNOWN_OPERATOR, expression);
 	}
 	
 	// The operands have now been parsed recursively; this parsing may have