Type constructor
A type constructor is a type-level function that takes types as parameters and produces a parameterized type.
Functional Programming in Scala, Second Edition
A type constructor is a type-level function that takes one or more types as parameters and produces a new parameterized type.
- How it is used
- Abstracts over parameterized computational and data contexts to define shared interfaces such as Foldable, Functor, Monad, and Free.
- How deep it goes
- Defines unary constructors, then works through partial application and type lambdas for two-argument State before applying constructors in abstractions.
- Examples
- Uses List, Option, Gen, Parser, State, Par, Function0, Async, TailRec, and Free as concrete constructor examples.
- What you can do after
- Apply it via Scala type aliases and type lambdas to supply one-argument constructors required by Monad instances.
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Functional Programming in JavaScript
An operation or definition that creates values of a parameterized type.
- How it is used
- Creates the container form used before chaining, flattening, or handling missing values in monadic code.
- How deep it goes
- Defines the constructor role and names its place in the monad interface, but stops short of formal type-system detail.
- Examples
- Uses Wrapper.of, Maybe.of, and Maybe.fromNullable as concrete constructors for wrapped, present, or absent values.
- What you can do after
- Build it from scratch as the entry point for values that will be mapped, joined, or safely handled later.
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Related concepts
- foldableused by · Foldable is a typeclass abstraction for data structures whose elements can be traversed and reduced to a result by folding operations.
- initializercontrasts with · An initializer is a function, declaration, or language construct that establishes the initial value or state of an object, value, computation, or process.
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