How Can I Convert Strings to Integers in C While Handling Conversion Errors?

Converting Strings to Integers with Boolean Failure in C

Problem:

Converting strings to integers in C often presents the problem of handling invalid conversions. This raises the need for an efficient method to perform such conversions with the ability to indicate failure.

Solution: Boost's Lexical Cast

Boost's lexical_cast library offers a robust solution for safe string-to-integer conversions. It throws an exception when encountering an invalid conversion:

<code class="cpp">#include <boost/lexical_cast.hpp>

try {
    int i = boost::lexical_cast<int>(s);
    // Success handling
} catch(...) {
    // Failure handling
}</code>

Alternative Without Boost: Standard Streams and Exceptions

If Boost is unavailable, you can use standard input/output stream operations with exceptions:

<code class="cpp">#include <iostream>
#include <sstream>
#include <string>

try {
    std::stringstream ss(s);
    int i;
    if ((ss >> i).fail() || !(ss >> std::ws).eof())
        throw std::bad_cast();
    // Success handling
} catch(...) {
    // Failure handling
}</code>

Faking Boost's Lexical Cast (Optional)

You can create a customized version of lexical_cast without using Boost:

<code class="cpp">template <typename T>
T lexical_cast(const std::string& s) {
    std::stringstream ss(s);
    T result;
    if ((ss >> result).fail() || !(ss >> std::ws).eof())
        throw std::bad_cast();
    return result;
}</code>

No-Throw Versions (Optional)

For no-throw versions, handle exceptions within the lexical_cast function:

<code class="cpp">template <typename T>
bool lexical_cast(const std::string& s, T& t) {
    try {
        t = lexical_cast<T>(s);
        return true;
    } catch (const std::bad_cast& e) {
        return false;
    }
}</code>

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