traverse a string to look for certain chars

This is a discussion on traverse a string to look for certain chars within the C++ Programming forums, part of the General Programming Boards category; Hey people I am trying to do a validation type thing for the names of people. I prompt for the ...

  1. #1
    Registered User cdkiller's Avatar
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    traverse a string to look for certain chars

    Hey people I am trying to do a validation type thing for the names of people. I prompt for the name and then validate it. I am using getline to store the string because some names contain spaces. i would like to check the string to make sure there are no unwanted chars like "@" and "," etc. so far i can traverse a string to find 1 character using name.find() i will paste the code below, but i cant seem to get that to find more than one char. how do i fix it?

    Code:
    int main ()
    {
    string name;
    int i = 0;
    int dot_appearances = 0;
    
    getline(cin, name, '\n');
    
    for(i = name.find(".", 0); i != string::npos; i = name.find(".", i))
    {
        dot_appearances++;
        i++;  
    }
    cout << dot_appearances;
    return 0;
    }

  2. #2
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    So, are you wanting it to find a different symbol other than a period, or just that it won't recognize more than one period?

  3. #3
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    find_first_of is a good alternative if you want to look for multiple characters at the same time.

  4. #4
    The superhaterodyne twomers's Avatar
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    I think the for loop would be better replaced with a while loop

    while( (i=name.find(".", i)) != string::npos ){ [...] }

    I think would do it. Just ++ i just before the end of the loop

  5. #5
    Registered User cdkiller's Avatar
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    well it already finds all the periods in the string. what i want it to do is find other stuff too. so for example if i prompt NAME: d@n T33ry Br0wn
    i want to be able to check that string and say its invalid based on the @, 3, 0 characters there. i also do not want to use that find method i pasted because i would have to type out an individual case for each char i want, there must be an easier way

  6. #6
    and the hat of wrongness Salem's Avatar
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    Use regular expressions.

    There are a couple of regular expression libraries you can use, eg
    http://www.boost.org/libs/regex/doc/syntax.html

    Basically, you describe a pattern which matches all possible valid inputs
    Eg.
    "\w+@" matches one or more word characters followed by a literal @
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    >> i would have to type out an individual case for each char i want, there must be an easier way
    That's what find_first_of allows you to do. Put all the chars into a single string, and you only need one loop.

  8. #8
    Registered User cdkiller's Avatar
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    thanks. that find_first_of looks promising. i think i can get that to do what i want.

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