Singleexpression

Singleexpression is a term used to describe a programming style or design in which the core computation is expressed as a single expression rather than a sequence of statements. In this approach, values are produced directly through evaluation of expressions, and composition of smaller expressions forms more complex behavior. The concept is common in expression-oriented and functional languages, where functions are often built by combining simple expressions and higher-order functions.

In practice, singleexpression aligns with languages and idioms that favor referential transparency and composability. Many languages enable a single-expression function or lambda to capture logic succinctly, even if full programs might use additional constructs for input, side effects, or data management. Examples include Haskell, where function definitions can be seen as single expressions; Lisp-like languages, which encourage expression-based design; Python via lambda expressions; JavaScript with arrow functions; and Scala with concise function literals.

Examples of single-expression constructs include: Haskell f x = x + 1; Python f = lambda x: x + 1; JavaScript const f = x => x + 1. These patterns illustrate how behavior can be expressed as a single evaluative unit, enabling straightforward composition and transformation.

Benefits of the singleexpression approach include conciseness, easier reasoning about pure computations, and a natural fit for equational reasoning and refactoring. Limitations arise when complex logic or stateful operations are required, potentially reducing readability and maintainability if forced into a single expression.

See also: expression-oriented programming, functional programming, lambda calculus, higher-order functions.