c++ strings. input validation

This is a discussion on c++ strings. input validation within the C++ Programming forums, part of the General Programming Boards category; I have this problem in my program! I need a function that fixes the input. If the string has white ...

  1. #1
    Registered User
    Join Date
    Aug 2004
    Posts
    10

    c++ strings. input validation

    I have this problem in my program! I need a function that fixes the input. If the string has white characters at the beginning. For example : if s=" hello" , i want to fix the string to be : "hello". I made this function fix_input but it seems to have a problem. Any ideas??

    Thank you
    Crashgr

    void fix_input(string &s)
    {
    string tmp;
    int i=0;

    while (s.at(i)==' ')
    i++;

    while(i<=s.length())
    {
    tmp+=s.at(i);
    i++;
    }

    s=tmp;
    }

    int main()
    {
    string input;

    getline(cin,input);

    if(!input.empty())
    {
    if (input.at(0)==' ')
    fix_input(input);

    cout<<input<<endl;
    }

    return 0;
    }

  2. #2
    Registered User jlou's Avatar
    Join Date
    Jul 2003
    Posts
    1,088
    What problem is it having? That information would help...

    If it is crashing or throwing an exception, it is because you go past the end of the string when you call at(i) with i = s.length(). Your loop should be while(i < s.length()) not while(i <= s.length()).

    Also, don't forget to include header files in your posted code, so it is easier for others to quickly copy your code and build it themselves.

  3. #3
    Registered User
    Join Date
    Aug 2004
    Posts
    10
    grrrrr!! I'm stupid!! Thank you jlou!! That was the problem!! And I swear that, this was the first thing i checked!! Thank you again.

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