First-class object
A first-class object is a language value that can be stored, passed, returned, and manipulated in the same general ways as other values.
Learn Concurrent Programming with Go
A first-class object is a value that a programming language allows to be stored, passed as an argument, returned from a function, or otherwise handled like other ordinary values.
- How it is used
- Uses channels as composable connections for message-passing pipelines and select-based concurrent behavior.
- How deep it goes
- Defines first-class channels and works through returned streams and a dynamically growing prime-filter pipeline.
- Examples
- Demonstrates periodic Tick/Tock channels selected together and a prime-number sieve that adds filter goroutines.
- What you can do after
- Apply it via Go channels to compose reusable stages and change a concurrent program’s channel topology at runtime.
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Secrets of the JavaScript Ninja, Second Edition
A value that can be assigned, passed as an argument, returned, and otherwise handled like an ordinary value.
- How it is used
- Uses first-class functions to explain why JavaScript functions can be placed where values are needed, including callback arguments.
- How deep it goes
- Explains assignable, passable, returnable, and invokable functions with code; defers detailed closure and scope mechanics.
- Examples
- Compares number and function literals in assignments and arguments, then contrasts function declarations with expressions.
- What you can do after
- Practice/perform it by placing function expressions in assignments, arguments, and return positions.
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Kotlin in Action, 2E
A first-class function is a function that can be stored in variables, passed as an argument, or returned from another function.
- How it is used
- Uses functions as values to parameterize behavior, remove duplication, and structure functional-style Kotlin code.
- How deep it goes
- Defines storing, passing, and returning functions, then works through lambda callbacks and returned calculators and predicates.
- Examples
- Uses a button click listener, a message-processing pipeline, shipping-cost calculators, and contact-list predicates.
- What you can do after
- Apply it via Kotlin lambdas and function types to pass or return behavior for callbacks, calculators, and filters.
Functional Programming in JavaScript
A function value that can be assigned, passed as an argument, and returned like other values in a language.
- How it is used
- Uses functions as reusable values for composing functional JavaScript and passing parameterized behavior.
- How deep it goes
- Defines function objects, variables, properties, constructors, and arguments, then stops short of detailed execution internals.
- Examples
- Demonstrates variable assignment, object methods, Function constructors, sorting callbacks, operation arguments, and returned functions.
- What you can do after
- Apply it by passing operations, selectors, printers, and callbacks into reusable JavaScript functions.
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Functional Programming in Scala, Second Edition
A first-class value is a value that can be represented, returned, stored, passed to functions, and otherwise manipulated like other values.
- How it is used
- Separates business logic from payment effects so purchases and charges can be reused and tested independently.
- How deep it goes
- Demonstrates representation, reuse, aggregation, and function passing, but does not develop the general theory of first-class values.
- Examples
- Uses Coffee, Charge, buyCoffee, buyCoffees, and coalesce to demonstrate explicit and combinable values.
- What you can do after
- Apply first-class values to separate effects, compose collection operations, and write reusable testable business logic.
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Learn Haskell by Example
A first-class function is a function that can be treated as a value, including being passed, returned, named, stored, or composed.
- How it is used
- Uses functions as reusable values for composing declarative programs and passing transformations between operations.
- How deep it goes
- Explains passing, returning, naming, storing, and composing functions, then demonstrates composition in GHCi and CSV output.
- Examples
- Uses a cake recipe analogy, GHCi composition expressions, composed function lists, and a CSV file-writing pipeline.
- What you can do after
- Apply function composition and partial application to build concise transformation pipelines, including CSV output actions.
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Data-Oriented Programming: Reduce software complexity
A first-class citizen is a value or language entity that can be represented, stored, passed, and manipulated in the same general ways as other values.
- How it is used
- Uses first-class data and fields to support generic manipulation, debugging, and reproducible database-backed behavior.
- How deep it goes
- Defines the idea through data collections, fields, late binding, and a worked REPL reproduction, without formal language-runtime internals.
- Examples
- Demonstrates captured catalog data, reproduced book-search calls, and a failing then improved 'Habit' query.
- What you can do after
- Diagnose/debug with it by capturing data arguments, reproducing calls in a REPL, and iterating against concrete database data.
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Related concepts
- functionincludes · A function is a defined operation that maps inputs to outputs and, when implemented as a callable program unit, may also produce effects.
- functional, stateless philosophyused by · Functional programming is a programming paradigm that expresses computation through the evaluation and composition of functions, typically favoring immutable data and minimizing mutable state and side effects.
- arithmetic operatorcontrasts with · An arithmetic operator is a programming-language operator that performs a numerical calculation on one or more operands.
- JavaScriptused by · JavaScript is a high-level, dynamically typed, multi-paradigm programming language standardized as ECMAScript and used for web and general-purpose programming.
- channelincludes · A channel is a typed Go communication and synchronization mechanism through which goroutines send and receive values.
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