singleL

singleL is a minimal, hypothetical programming language used in academic discussions of language design and formal semantics. Conceived as a teaching aid, it emphasizes a small core of constructs over a feature-rich surface syntax, enabling precise reasoning about evaluation rules and type checking without extraneous complexity.

The design goal of singleL is to illustrate how a usable language can be built from a compact set of elements. Its lexicon favors single-letter identifiers and a deliberately limited keyword set, with the idea that programmers focus on semantics rather than syntax. The language typically targets a simple, statically typed core and a deterministic evaluation strategy.

In singleL, programs are composed of expressions built from a small set of constructs such as variables, function abstractions, and applications. A conventional static type system assigns simple types to expressions, and evaluation follows a defined strategy, commonly call-by-value. A minimal standard library provides illustrating features such as basic data types and basic input/output in a restrained, didactic form.

Example (illustrative, in plain form): L x. x represents the identity function; the application (L x. x) 5 evaluates to 5 in a closed context.

As a teaching tool, singleL has appeared in computer science pedagogy and theoretical discussions but has no standardized implementation or official specification. Prototypes and exercises are used to demonstrate concepts such as reduction, typing, and program equivalence. Related topics include lambda calculus and minimal functional languages.