recordtypes

Record types are a common composite data type that groups named fields, each with a type. A record value consists of a fixed set of labeled fields accessible by name. They model structured data such as a person’s profile or a coordinate pair.

Fields are defined at the type level; records are constructed by supplying values for each field. Depending on the language, records may be immutable or mutable, and fields are typically accessed via dot notation or through pattern matching.

Typing varies by language. Some languages use structural typing, where two records are compatible if their field names and types match; others use nominal typing with explicit declarations. Some systems support open or extensible records, enabling additional fields via row polymorphism.

Record types are related to structs in imperative languages and to labeled algebraic data types in functional languages. They contrast with tuples (unnamed) and with maps or dictionaries (dynamic keys). Design choices affect field visibility, mutability, and how records interact with functions.

Common examples include ML and OCaml records; Haskell records; TypeScript interfaces; Rust structs; Go structs; and database contexts where a row corresponds to a record. Syntax and features such as pattern matching on fields or open records vary by language.