An expression-oriented programming language is a

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

in which every (or nearly every) construction is an expression and thus yields a value. The typical exceptions are macro definitions,

preprocessor In computer science, a preprocessor (or precompiler) is a Computer program, program that processes its input data to produce output that is used as input in another program. The output is said to be a preprocessed form of the input data, which i ...

commands, and declarations, which expression-oriented languages often treat as

statements Statement or statements may refer to: Common uses *Statement (computer science), the smallest standalone element of an imperative programming language * Statement (logic and semantics), declarative sentence that is either true or false *Statement, ...

Lisp Lisp (historically LISP, an abbreviation of "list processing") is a family of programming languages with a long history and a distinctive, fully parenthesized Polish notation#Explanation, prefix notation. Originally specified in the late 1950s, ...

and

ALGOL 68 ALGOL 68 (short for ''Algorithmic Language 1968'') is an imperative programming language member of the ALGOL family that was conceived as a successor to the ALGOL 60 language, designed with the goal of a much wider scope of application and ...

are expression-oriented languages. Pascal is not an expression-oriented language. All

functional programming In computer science, functional programming is a programming paradigm where programs are constructed by Function application, applying and Function composition (computer science), composing Function (computer science), functions. It is a declarat ...

languages are expression-oriented.

Criticism and prevention

Critics, including language designers, blame expression-orientation for an entire class of programming mistakes wherein a programmer accidentally codes an assignment ''expression'', which replaces a variable with an expression rather than testing it for

equality Equality generally refers to the fact of being equal, of having the same value. In specific contexts, equality may refer to: Society * Egalitarianism, a trend of thought that favors equality for all people ** Political egalitarianism, in which ...

with that expression. The designers of Ada and

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

prevent this type of mistake by restricting control expressions to those that evaluate strictly to the

boolean data type In computer science, the Boolean (sometimes shortened to Bool) is a data type that has one of two possible values (usually denoted ''true'' and ''false'') which is intended to represent the two truth values of logic and Boolean algebra. It is na ...

. The designers of Python implemented assignment as a statement rather than an expression, thus prohibiting assignment from nesting inside any other statement or expression. (Until version 3.8 added 'assignment expressions', with a different syntax.) In some expression-oriented languages, expressions that merely cause

side effects In medicine, a side effect is an effect of the use of a medicinal drug or other treatment, usually adverse but sometimes beneficial, that is unintended. Herbal and traditional medicines also have side effects. A drug or procedure usually used ...

return

void type The void type, in several programming languages, more so curly bracket programming languages derived from C and ALGOL 68, is the return type of a function that returns normally, but provides no result value to its caller. Usually such functi ...

Examples

BLISS BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C ...

Icon An icon () is a religious work of art, most commonly a painting, in the cultures of the Eastern Orthodox, Oriental Orthodox, Catholic Church, Catholic, and Lutheranism, Lutheran churches. The most common subjects include Jesus, Mary, mother of ...

* ML *

Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed ...

* Rebol *

Ruby Ruby is a pinkish-red-to-blood-red-colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapph ...

Elixir An elixir is a sweet liquid used for medical purposes, to be taken orally and intended to cure one's illness. When used as a dosage form, pharmaceutical preparation, an elixir contains at least one active ingredient designed to be taken orall ...

* Erlang *

Haskell Haskell () is a general-purpose, statically typed, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research, and industrial applications, Haskell pioneered several programming language ...

Rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...

* Scala *

Smalltalk Smalltalk is a purely object oriented programming language (OOP) that was originally created in the 1970s for educational use, specifically for constructionist learning, but later found use in business. It was created at Xerox PARC by Learni ...

* Kotlin *

OCaml OCaml ( , formerly Objective Caml) is a General-purpose programming language, general-purpose, High-level programming language, high-level, Comparison of multi-paradigm programming languages, multi-paradigm programming language which extends the ...

References

{{Programming paradigms navbox Programming language classification

Criticism and prevention

Examples

See also

References