Typed functions

Typed functions enforce explicit parameter and return types, guaranteeing data contracts for improved code reliability and compile-time error detection.

Typed functions formalize a function's signature: they define the domain (input types) and range (output type). This core concept, often denoted as $A \to B$ in theoretical settings like the simply typed lambda calculus, is crucial for program correctness. In practice, languages like TypeScript and C# leverage static type systems to catch type errors during compilation, not runtime. This strict contract prevents unexpected behavior, such as passing a `string` to a function expecting a `number`, significantly boosting code quality and maintainability across large-scale projects.

https://en.wikipedia.org/wiki/Function_type