Concept
Miranda is a lazy, purely functional programming language designed by David Turner as a successor to his earlier programming languages SASL and KRC, using some concepts from ML and Hope. It was produced by Research Software Ltd. of England (which holds a trademark on the name Miranda) and was the first purely functional language to be commercially supported. Miranda was first released in 1985 as a fast interpreter in C for Unix-flavour operating systems, with subsequent releases in 1987 and 1989. It had a strong influence on the later Haskell language. Turner stated that the benefits of Miranda over Haskell are: "Smaller language, simpler type system, simpler arithmetic". In 2020 a version of Miranda was released as open source under a BSD licence. The code has been updated to conform to modern C standards (C11/C18) and to generate 64-bit binaries. This has been tested on operating systems including Debian, Ubuntu, WSL/Ubuntu, and macOS (Catalina). Miranda is a lazy, purely functional programming language. That is, it lacks side effects and imperative programming features. A Miranda program (called a script) is a set of equations that define various mathematical functions and algebraic data types. The word set is important here: the order of the equations is, in general, irrelevant, and there is no need to define an entity prior to its use. Since the parsing algorithm makes intelligent use of layout (indentation, via off-side rule), bracketing statements are rarely needed and statement terminators are unneeded. This feature, inspired by ISWIM, is also used in occam and Haskell and was later popularized by Python. Commentary is introduced into regular scripts by the characters || and continue to the end of the same line. An alternative commenting convention affects an entire source code file, known as a "literate script", in which every line is considered a comment unless it starts with a > sign. Miranda's basic data types are char, num and bool.
