How to use std::expected?

To use the std::expected class template, follow the given steps:

  1. Create an instance of std::expected with the expected value type (T) and the error type (E).
  2. In case of an error, return an instance of std::expected with the error type (E).
  3. When an operation succeeds, return an instance of std::expected with the expected value (T).
  4. Utilize methods like has_value() and value() to access the value or error() to obtain the error, as needed.

C++23 – Header

C++23, the next major version of the C++ programming language, brings several exciting features and enhancements. One of the significant additions in C++23 is the <expected> header, which aims to improve error handling and make code more robust and readable. In this article, we will explore the feature of <expected> header, its purpose, and how it simplifies error handling in C++.

Problem with Error Handling

Error handling in C++ has historically been a complex and error-prone task. C++ has exceptions and error codes, but choosing the right approach and implementing error handling consistently across a codebase can be challenging. Additionally, exceptions can introduce performance overhead in certain scenarios.

Similar Reads

Header in C++

The header in C++23 introduces a new way to handle errors and expected values. It is inspired by similar constructs in other programming languages, such as Rust’s Result and Swift’s Result types. The primary goal of is to provide a more explicit and structured way to handle expected values and errors without relying solely on exceptions or error codes....

1. std::expected Class Template

The std::expected is a class template in C++ that serves as a mechanism for managing functions that may return either a valid result or an error. It is a wrapper that is particularly useful in scenarios where exceptions might not be the preferred error-handling approach....

2. std::unexpected Class Template

The std::unexpected is not a standalone class but rather a concept used with std::expected. It helps to define how unexpected errors are handled within a specific context....

How to use std::expected?

To use the std::expected class template, follow the given steps:...

Examples

Below given is the example code that uses expected in C++:...

Advantages of using std::expected

...

Conclusion

...