Polymorphic dispatch
Polymorphic dispatch is runtime selection of an operation implementation based on a call's arguments, function value, or context.
Data-Oriented Programming: Reduce software complexity
A dispatch function is a function that defines a multimethod's signature, validates its arguments, and emits a value used to select an implementation.
- How it is used
- Uses dispatch functions to separate multimethod call signatures and selection logic from method implementations.
- How deep it goes
- Explains signatures, validation, single, multiple, and dynamic dispatch with JavaScript examples, but does not develop their implementation machinery.
- Examples
- Demonstrates animal greetings selected by type, animal-language pairs, and animal type combined with name length.
- What you can do after
- Build multimethods whose behavior varies by one argument, several arguments, or runtime-derived values.
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Clojure: The Essential Reference
A dispatch function is a callable operation that selects and invokes an implementation based on an argument's dispatch value.
- How it is used
- Selects behavior for data-driven operations and supports flexible polymorphism beyond type-based method selection.
- How deep it goes
- Defines dispatch functions, implementations, hierarchies, ambiguity resolution, extension, removal, inspection, and failure behavior.
- Examples
- Demonstrates expression evaluation, custom operation hierarchies, runtime extension, method removal, ambiguity resolution, recursion, and exceptions.
- What you can do after
- Build it from scratch using defmulti, defmethod, custom hierarchies, default methods, and protocol extensions.
Read how Clojure: The Essential Reference explains polymorphic dispatch →
Related concepts
- multiple dispatchused by · Multiple dispatch is a method-selection mechanism that chooses an implementation based on the types of multiple arguments.
- multimethodused by · A multimethod is a dispatch mechanism that selects an implementation by applying a dispatch function to multiple arguments, often using their runtime types or values.
- defprotocolproduced by · defprotocol is a Clojure macro that defines a protocol interface supporting dynamic dispatch independently of Java class inheritance.
- contractcontrasts with · An API contract is a specification of the operations, data, and behavioral expectations that govern interactions between software components.
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