How Can I Efficiently Detect Numeric Strings in C ?

Detecting Numeric Strings in C

Determining whether a string represents a numeric value can be a ubiquitous requirement in various programming scenarios. For instance, in the context of data file parsing, identifying numeric lines becomes crucial. While various methods exist, this article focuses on two efficient approaches to accomplishing this task in the realm of C .

Iterative Approach

The simplest and most straightforward method involves iterating through each character in the string. If any character is non-digit, the string is deemed not numeric.

bool is_number(const std::string& s) {
    for (char c : s) {
        if (!std::isdigit(c)) {
            return false;
        }
    }
    return true;
}

C 11's find_if

Modern C proponents may prefer utilizing find_if for a concise implementation. This approach leverages lambda expressions to search for the first non-digit character, returning false if found and true if none are present.

bool is_number(const std::string& s) {
    return std::find_if(s.begin(), s.end(), [](unsigned char c) { return !std::isdigit(c); }) == s.end();
}

Caveats

It's important to note that both techniques assume only positive integers. To handle negative integers or fractions, a more comprehensive solution is recommended, potentially utilizing third-party libraries like Boost or C 20's header.

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