Thread: Searching a file for a String Occurence

Originally Posted by laserlight

The use of std::toupper (as opposed to the global toupper) is problematic in this case, though the exact reason eludes me at the moment. (Type mismatch? I know this has been discussed before.) Josuttis suggests just defining a function that compares characters without regard for case, and then use say, equal(), e.g.,

Code:

bool noCaseEqualChar(char lhs, char rhs)
{
    return std::toupper(lhs) == std::toupper(rhs);
}

bool noCaseEqual(const std::string& lhs, const std::string& rhs)
{
    return lhs.size() == rhs.size()
        && std::equal(lhs.begin(), lhs.end(), rhs.begin(), noCaseEqualChar);
}

We could use function object template classes instead and thus not have to resort to the different function names.

These functions are absolutely perfect for use when comparing std::strings.

Thanks laserlight!

Originally Posted by laserlight

Josuttis suggests just defining a function that compares characters without regard for case, and then use say, equal(), e.g.,

What page does Josuttis talk about that. I can't find it.

Thanks in advance!

Once again, thanks.

This might be useful to someone:

Code:

/*******************************************************************************
*   Usage:
*       to_lower(std::string); Converts std::string to lowercase
*       to_upper(std::string); Converts std::string to uppercase
*******************************************************************************/
#include <locale>
#include <string>

// to_lower(std::string)
template <typename Char, typename Traits>
    std::basic_string<Char, Traits> &to_lower(std::basic_string<Char, Traits>
    &str, std::locale loc = std::locale())
{
    typedef std::basic_string<Char, Traits> string;
    typedef std::ctype<Char> char_type;
    char_type const * the_type_ptr = &std::use_facet<char_type>(loc);
    for (typename string::size_type i = 0; i <str.size(); ++i)
    {
        str[i] = the_type_ptr->tolower(str[i]);
    }
    return (str);
}

// to_upper(std::string)
template <typename Char, typename Traits>
    std::basic_string<Char, Traits> &to_upper(std::basic_string<Char, Traits>
    &str, std::locale loc = std::locale())
{
    typedef std::basic_string<Char, Traits> string;
    typedef std::ctype<Char> char_type;
    char_type const * the_type_ptr = &std::use_facet<char_type>(loc);
    for (typename string::size_type i = 0; i <str.size(); ++i)
    {
        str[i] = the_type_ptr->toupper(str[i]);
    }
    return (str);
}

Cheers!

This is what I settled on:

Code:

void searchRecords(std::ifstream &fin, std::string &searchString, 
                   OldStudentData &obj, long recordNum)
{
    fin.seekg(sizeof(OldStudentData) * recordNum, std::ios::beg);
    fin.read((char *) &obj, sizeof(OldStudentData));

    std::string personName(obj.studentname);

    if(noCaseEqual(searchString, personName))
    {
        // Do some stuff in here!
    }
}

bool noCaseEqual(const std::string &lhs, const std::string &rhs)
{
    return lhs.size() == rhs.size() 
        && std::equal(lhs.begin(), lhs.end(), rhs.begin(), noCaseEqualChar);
}

bool noCaseEqualChar(char lhs, char rhs)
{
    return std::toupper(lhs) == std::toupper(rhs);
}

Thanks for all of the help! Any Ideas on refinement?