resultatyper

Resultatyper, or result types, refer to type constructs that model the outcome of a computation. They typically represent one of two possibilities: a successful value or some form of error or alternative result. This approach makes outcomes explicit and predictable, reducing the reliance on exceptions for control flow.

Characteristics of resultatyper include that they are often algebraic data types or sum types. A value of a result type can be in a success variant carrying a value, or in an error variant carrying information about what went wrong. They are usually generic, allowing the success branch to hold any type and the error branch to hold an error type appropriate to the context. Access to the contained value is achieved through pattern matching, or by functional combinators that map, chain, or recover from errors.

Common language implementations include:

- Rust: Result<T, E> with Ok(T) for success and Err(E) for failure.

- Haskell: a similar pattern via Either a e or a custom Result type.

- Swift: Result<Success, Failure: Error> with success and failure cases.

- Kotlin and other languages provide comparable constructs or patterns, sometimes using Optional/Optional-like types for absence and separate error handling mechanisms.

Usage typically involves explicit handling of both branches, often through map and flatMap (or andThen) operations, or by unwrap-like methods that propagate errors. Benefits include clearer error propagation, easier reasoning about failure modes, and better composability of operations. Drawbacks can include boilerplate, nested result handling, and potential verbosity in deeply chained computations. Resultatyper form a central pattern in modern languages to express robust, predictable error handling without relying on unchecked exceptions.