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

wolf4earth
Inspired by this thread about arcade games - which I initially misread as favorite arcade game soundtracks - I wanted to ask about your f...
New
chasekaylee
Just like the title says :smiley: which courses you find that have had the most impact in the span of your career as a developer?
New
AstonJ
Do the test and post your score :nerd_face: :keyboard: If possible, please add info such as the keyboard you’re using, the layout (Qw...
New
AstonJ
Are you a touch typist? :keyboard: poll If you haven’t checked your typing speed yet, you can do so here here :smiley:
New
DevotionGeo
The Odin programming language is designed with the intent of creating an alternative to C with the following goals: simplicity high per...
New
dwaynebradley
For those that are interested, Snyk (developer security tool) announced support for Elixir earlier this week: Just thought I’d pass it...
New
Exadra37
A modern streaming platform for mission critical workloads Redpanda is a Kafka® compatible event streaming platform. No Zookeeper®, no JV...
New
New
foxtrottwist
A few weeks ago I started using Warp a terminal written in rust. Though in it’s current state of development there are a few caveats (tab...
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

Other popular topics Top

DevotionGeo
I know that these benchmarks might not be the exact picture of real-world scenario, but still I expect a Rust web framework performing a ...
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
dimitarvp
Small essay with thoughts on macOS vs. Linux: I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
New
Maartz
Hi folks, I don’t know if I saw this here but, here’s a new programming language, called Roc Reminds me a bit of Elm and thus Haskell. ...
New
PragmaticBookshelf
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
PragmaticBookshelf
Author Spotlight: VM Brasseur @vmbrasseur We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
PragmaticBookshelf
Author Spotlight: Karl Stolley @karlstolley Logic! Rhetoric! Prag! Wow, what a combination. In this spotlight, we sit down with Karl ...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New
PragmaticBookshelf
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
New
Fl4m3Ph03n1x
Background Lately I am in a quest to find a good quality TTS ai generation tool to run locally in order to create audio for some videos I...
New