Singlefunction

Singlefunction is a software design approach that structures a component, service, or library around a single public function that serves as the primary entry point. The goal is to maximize cohesion and minimize the API surface, so users interact with one well-defined function rather than a collection of methods.

In practice, singlefunction can be implemented by exporting one main function from a module, with internal helpers used only by that function. In web services, a single handler may orchestrate a sequence of operations, delegating to private routines, while ensuring the external API remains a single callable entry. In data processing, a pipeline can be organized so that a single transformation function represents the visible interface, with composition happening behind the scenes.

Rationale for the approach centers on clarity and testability. A narrow interface makes intent easier to understand, simplifies mocking or stubbing in tests, and clarifies data flow. It can also facilitate reuse by isolating the core logic behind a stable contract, while keeping implementation details opaque to consumers.

Criticisms include potential over-indirection or the tendency to squeeze complex domains into a single entry point, which can lead to a bloated or less readable function if not managed carefully. The pattern is most effective in narrow domains with well-defined responsibilities and where the benefits of a minimal API outweigh the costs of additional orchestration.

Related concepts include the single responsibility principle, high cohesion, and minimal API design. See also function composition and modular programming.