How to Check for Numeric Character Content in C Strings and char* Variables?

Checking for Numeric Character Content in C Strings and char* Variables

When working with strings in C , it is often necessary to determine if a given sequence of characters contains only numeric digits. This can be achieved using various methods, each with its own advantages and drawbacks.

For std::string objects, one approach is to utilize the std::find_first_not_of() function. This function searches for the first character in the string that does not match any of the characters specified in its input. By passing a string containing only the numeric characters (e.g., "0123456789"), we can determine if the input string contains any non-numeric characters.

<code class="cpp">bool is_digits(const std::string &str) {
    return str.find_first_not_of("0123456789") == std::string::npos;
}</code>

Alternatively, for both std::string and char* variables, we can use the std::all_of() function. This function takes a range of elements and a predicate (a function that returns a boolean value for each element). By applying the ::isdigit() predicate, which returns true for numeric characters, we can verify if all characters in the sequence satisfy this condition.

<code class="cpp">bool is_digits(const std::string &str) {
    return std::all_of(str.begin(), str.end(), ::isdigit); // C++11
}</code>

These methods provide efficient ways to check for numeric character content in both std::string and char* variables. The choice of approach depends on the specific requirements and preferences of the developer.

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