Combinator
A combinator is a function or computational construct that combines, composes, or transforms smaller functions or computations into a larger operation.
Functional Programming in Scala, Second Edition
A combinator is a compositional operation that builds a larger computation from smaller functions or computational structures.
- How it is used
- Builds larger parallel computations, generators, properties, and parsers by composing smaller operations.
- How deep it goes
- Develops API refinement, primitive-versus-derived distinctions, laws, and implementations while deferring representation in algebraic parser design.
- Examples
- Uses parallel choice and lazyUnit, generator construction, property conjunction, and repeated alternative parsers.
- What you can do after
- Build composite operations from a minimal algebra and refine overly specific APIs into reusable combinators.
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Functional Programming in JavaScript
A higher-order function that combines other functions to coordinate control flow or transformation in a functional program.
- How it is used
- Coordinates functional control flow without placing business logic or local variables inside the coordinating functions.
- How deep it goes
- Defines identity, tap, alternation, sequence, and fork with JavaScript implementations and worked compositions.
- Examples
- Uses student lookup, logging during validation, average-grade calculation, equality comparison, and Lodash chained transformations.
- What you can do after
- Apply combinators via Ramda and Lodash to compose transformations, choose alternatives, sequence actions, and combine results.
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Functional Design and Architecture: Examples in Haskell
A combinator is a function or expression-building operation that combines smaller computational elements into a larger computation.
- How it is used
- Organizes functional interfaces and embedded domain-specific languages around small operations that compose into larger computations.
- How deep it goes
- Defines the compositional principle and gives representative APIs, but stops short of formal category-theoretic derivations or implementation internals.
- Examples
- Uses mapM, sequence, replicateM, lenses, and reactive streams as examples of composable functional operations.
- What you can do after
- Evaluate/understand functional interfaces by recognizing when small operations compose into reusable domain-specific behavior.
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Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
A higher-order function or construct that builds a new operation by composing or transforming existing ones.
- How it is used
- Transforms observable streams into more specific streams by composing operations such as mapping and filtering.
- How deep it goes
- Defines combinators through subscription and new-observable creation, then walks through filtering; error and completion forwarding are deferred.
- Examples
- Uses a clock stream formatted into distinct time strings and a number stream filtered to odd values.
- What you can do after
- Build it from scratch by subscribing to an existing observable and forwarding transformed or selected values through a new observable.
Related concepts
- trampolineincludes · A trampoline is a control mechanism that repeatedly invokes returned functions or computation steps until a final value is produced.
- parser combinatorincludes · A parser combinator is a compositional function or operation that constructs larger parsers from existing parsers.
- higher-order functionuses · A higher-order function is a function that accepts functions as arguments, returns functions as results, or both.
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