Racket vs. Scheme vs. Unlambda vs. ZenScript Comparison Chart

Racket is a general-purpose, multi-paradigm programming language that serves as a modern dialect of Lisp and a descendant of Scheme. It is designed as a platform for programming language design and implementation, enabling developers to create new domain-specific and general-purpose languages. Racket's core language includes features such as macros, modules, lexical closures, tail calls, delimited continuations, parameters (fluid variables), software contracts, green threads, and OS threads. The language also comes with primitives, such as event spaces and custodians, which control resource management and enable the language to act like an operating system for loading and managing other programs. Further extensions to the language are created with the powerful macro system, which, together with the module system and custom parsers, can control all aspects of a language. Most language constructs in Racket are implemented as macros in the base language.

Unlambda is a programming language. Nothing remarkable there. The originality of Unlambda is that it stands as the unexpected intersection of two marginal families of languages. Functional programming languages, of which the canonical representative is Scheme (a Lisp dialect). This means that the basic object manipulated by the language (and indeed the only one as far as Unlambda is concerned) is the function. Rather, Unlambda uses a functional approach to programming: the only form of objects it manipulates are functions. Each function takes a function as an argument and returns a function. Apart from a binary “apply” operation, Unlambda provides several built-in functions (the most important ones being the K and S combinators). User-defined functions can be created, but not saved or named, because Unlambda does not have any variables.