harwind

harwind

C++ String to Integer Conversion

I’m working on a C++ program where I need to convert a string containing a numeric value into an integer. I want to ensure that this conversion is handled correctly and safely, especially when dealing with potential exceptions or invalid input.

Here’s a simplified example of what I’m trying to do:

#include <iostream>
#include <string>

int main() {
    std::string str = "12345"; // This could be any numeric string.

    // How can I safely convert the string 'str' to an integer?

    int num = ???; // The converted integer should be stored here.

    std::cout << "Converted integer: " << num << std::endl;

    return 0;
}

In this code, I have a string str containing a numeric value. I want to convert this string into an integer variable num . However, I want to handle potential issues gracefully, such as cases where the string is not a valid integer. Could you offer a C++ code sample illustrating the proper and secure approach to convert a string to an integer while managing any potential exceptions or errors? I appreciate you helping me. I attempted to visit multiple sites like Scaler to locate the answer, but I was unable to do so. Thank you.

Most Liked

gulshan212

gulshan212

Well, I can see some logical issues with your code.
Can you try this code and confirm wether it is working or not.

#include <iostream>
#include <string>
#include <stdexcept> // Include this for std::invalid_argument and std::out_of_range

int main() {
    std::string str = "12345"; // This could be any numeric string.

    int num = 0; // The converted integer will be stored here.

    try {
        num = std::stoi(str);
        std::cout << "Converted integer: " << num << std::endl;
    } catch (const std::invalid_argument& e) {
        std::cerr << "Invalid argument: " << e.what() << std::endl;
    } catch (const std::out_of_range& e) {
        std::cerr << "Out of range: " << e.what() << std::endl;
    }

    return 0;
}

Thanks

Eiji

Eiji

I’m not a senior C++ developer, so I have no idea about the best way, but this should work:

#include <iostream>
#include <string>
#include <cctype>

int main() {
  std::string str = "123";
  // str[0] - gets the first character
  // isdigit(character) - checks if character is a digit
  // stoi throws invalid_argument exception
  // if string does not start with a digit
  if (isdigit(str[0])) {
    /*
    stoi means "String TO Integer"
    you can easily change it to for example:
      * stof ("String TO Float"),
      * stol ("String TO Long")
      * and so on …
    */
    int num = std::stoi(str);
    std::cout << "[DONE] Converted integer: " << num << std::endl;
  } else {
    std::cout << "[ERROR] Invalid input string: " << str << std::endl;
  }

  return 0;
}

Helpful resources

  1. Reference : string : stoi
  2. Reference : cctype : isdigit
Eiji

Eiji

For me looks good. I have tested it on my MX Linux distribution.

It’s interesting how much the code says about it’s author. In my case 7 years in Elixir gives result …

  1. Even if somehow I remember somewhat about try/catch I was still looking for a “better” solution, so I have added one extra dependency for a single isdigit call. :sweat_smile:

  2. std:err of course! When I saw your code I have reminded it immediately. :older_man:

  3. stdexcept is interesting. Maybe I have used it, but I don’t remember it much especially e.what() call. I guess that I haven’t used multiple catch blocks before in C++. :bulb:

  4. out_of_range error handling is simple, but also brilliant idea. I’m not surprised that I wasn’t thinking about such edge case since in Elixir we have just Integer for all well … integers (no small or big ones). :+1:

  5. I only wonder why you define num variable outside of try block having in mind it’s only usage is within it, but that’s definitely not the most important thing. :thinking:

So much to learn in such a small code, thanks! :open_book:

Adding additional links below to the documentation pages:

  1. Reference : stdexcept : invalid_argument
  2. Reference : stdexcept : out_of_range

Where Next?

Popular General Dev topics Top

AstonJ
Thread to discuss ideas and thoughts on how developers might be able help in the Coronavirus pandemic.
New
KyleHunter
What is a good language for beginners to make apps like snapchat and instagram?
New
AstonJ
What do you think needs fixing in the digital / computer science sphere?
New
Exadra37
I am a Linux user since 2012, more or less, and I always use Ubuntu on my computers, and my last 2 laptops have been used Thinkpads, wher...
New
AstonJ
Do you think it’s worth worrying about? Do you think it’s going to be an even bigger issue in future? If so what can the teams of smaller...
New
jaeyson
Not trying to add more mess here but, reddit has ELI5 but i wanted to know if it’s okay to ask Elixir-specific (or outside of it) in a si...
New
malloryerik
With 100% less blockchain. I went searching for a lightweight immutable database that could be audited and ran into this. I guess this ...
New
DevotionGeo
Amazon CodeWhisperer is an alternative to GitHub Copilot, and it’s free!
New
harwind
I’m working on a C++ program where I need to convert a string containing a numeric value into an integer. I want to ensure that this conv...
New
Margaret
Hello DevTalk Community! Once again, The Pragmatic Programmers are looking for developers who’d like to help shape the future of our boo...
New

Other popular topics Top

AstonJ
SpaceVim seems to be gaining in features and popularity and I just wondered how it compares with SpaceMacs in 2020 - anyone have any thou...
New
Rainer
My first contact with Erlang was about 2 years ago when I used RabbitMQ, which is written in Erlang, for my job. This made me curious and...
New
AstonJ
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
New
Margaret
Hello content creators! Happy new year. What tech topics do you think will be the focus of 2021? My vote for one topic is ethics in tech...
New
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
New
New
PragmaticBookshelf
Author Spotlight: Karl Stolley @karlstolley Logic! Rhetoric! Prag! Wow, what a combination. In this spotlight, we sit down with Karl ...
New
New