The string length function returns an unsigned integer so you are probably trying to assign an unsigned integer to a signed (the default type) integer. You can do one of 2 things, have your value holding length be unsigned:

string str;
unsigned int n = str.length();

or use the static cast described under the warnings question.

Here are the following rule we used for defining palindromes.

A palindrome must consist of at least one character (after removing punctuation and white space).

Some students have asked "Doesn't it make sense to call the empty string a palindrome?" and the answer is yes, it does make sense, but in this project we DEFINE it NOT to be a palindrome. Sometimes this happens. A definition may not meet your intuition or perhaps even the official definition, but is the one being used in a project. (For example, non-alphanumeric non-white space isn't exactly a good definition for punctuation, but it is convenient to define it that way).

There are two errors students have encountered. One has to do with the fact that length() and size() return unsigned int (for nearly every STL class that uses these methods--but in this case, for strings), and the other is that toupper() and tolower() return int rather than char.

If you use length() or size() methods on string objects, in conjunction with looping variables of type int, you will run into a problem. length() and size() return unsigned int. Compilers complain that int and unsigned int are not compatible types. To solve, use static casting.

// WRONG!  size() returns unsigned int---looping variable is int! TYPE MISMATCH!
string str = "foo";
for ( int i = 0; i < str.size(); i++ )
  cout << str[ i ] << endl;

// BETTER : static cast
for ( int i = 0; i < static_cast<int>( str.size() ); i++ )
  cout << str[ i ] << endl;

   static_cast( stuff )

The other problem stems from toupper and tolower. These functions return int, instead of char, so it complains that you are losing some data by casting from a large type (an int, which contains at least 4 bytes) to a smaller type (a char, which contains 1 byte).

Again, static cast to remove the error.

    char ch = 'a';

    // toupper, unusually enough, returns an int.  The static cast
    // converts it back to a char.

    char ch2 = static_cast<char>( toupper( ch ) );

Yes. You want to be careful when using C++ strings. For example, although it happens to be permissible to modify the characters of a C++ string, you generally use concatentation (the + operator) to increase the size of the string (there are other ways).

Here are two useful functions you can use:

   char ch = 'A';
   string str( 1, ch );  // constructor to convert character to string

   string( 1, ch );  // constructor to convert character to string without declaring variable

   string str;  // empty string
   char ch;
   cin >> ch;
   while ( ch != '?' )
     str += string( 1, ch );  // Concatenate to str, one character at a time

   string substr( int start, int length );

   string str = "catalog";
   string s2 = str.substr( 2, 3 );

   cout << s2 << endl; // Prints "tal"

Yes, it does. However, it is the standalone (non member function) version. The prototype looks like:

istream & getline( istream &is, string & str, char delimiter );

Because some of the methods in Palindrome are const, your iterators must be const. So instead of defining iterator, use const_iterator or const_reverse_iterator.

• vector<int>::const_iterator cit;
• vector<int>::const_reverse_iterator crit;

Class accounts can only be given out to students officially registered in the course and can only be given out in person either during class or lab (the one for which you are registered) or in the TA's (who teaches your lab section) office hours (which start next week - see the class webpage for further details regarding office hours).

Note that you can actually start practicing your Unix and programming skills even if you do not have an official class account - WAM accounts (which all students should have - if not go to www.wam.umd.edu to find out how to get one) are very similar to the class accounts that we provide in that they are Unix systems. The one main difference is that they do not have the cxx compiler, but they do have the g++ compiler which is very similar.

A FAQ is a list of Frequently Asked Questions and in particular the FAQ's for projects in this class will have questions listed in reverse chronological order (meaning the most recent question will appear at the top of the FAQ list and the first question asked/answered will appear at the bottom of the list).

Project #0 is due by 11pm on Thursday, September 12th, 2002. Note: any project may be turned in late up to 2 days as specified on the class syllabus. For details regarding the late policy and any penalties associated with submitting late projects please see the class syllabus.