C++ Only execute toLowercase conversion when template is of type string

Question

Good day,

I am writing a simple C++ Linked List using templates. I have got everything working, but I wanted to add to the functionality by making it case insensitive by converting all characters to lowercase for when the template is of type string.

So, I wrote the following snippet to handle any word and convert it to all lower cases:

        #define TEMPLATE string // changing this changes the template type in the rest of the program
        Stack <TEMPLATE> s; //not used in this example, but just to show that I have an actual template for a class declared at some point, not just a definition called TEMPLATE
        TEMPLATE word; // User inputs a word that is the same type of the Linked List Stack to compare if it is in the Stack.
        cin >> word; // just showing that user defines word
        for (unsigned int i = 0; i < word.length(); i++)
        {
            if (word.at(i) >= 'A' && word.at(i) <= 'Z')
                word.at(i) += 'a' - 'A';
        }

The problem is that when the TEMPLATE of my Stack, and subsequently the compared word to the stack is not of type string, then it obviously throws error messages because the for loop was written specifically to look at strings.

So, is there a way I could make this function more generic so that any type can be passed? (I don't think so, since there would be no error checking for ints, etc. String is the only one that relies on this)

Or, is there a way that I can only execute the above code when my Template for my Stack and compared variable is of type string?

I looked at exception handling, except I'm very much used to how Python works and so I could not figure out exactly how to implement in C++ instead.

Just as a side note, I am not using any built in functions to convert the string to all lower cases, so that is not an option either and I am not looking for recommendations of those.

Answer 1

Create overloads to normalize your data:

std::string normalize(const std::string& s) {
    std::string res(s);
    for (auto& c : res) {
        c = std::tolower(c);
    }
    return res;
}

template <typename T>
const T& normalize(const T& t) { return t; }