Type compatibility
Type compatibility is the relationship in which values of one type can be used where another type is expected under applicable language rules.
Building User-Friendly DSLs
A relation between types specifying whether values of one type can be used where values of another type are expected.
- How it is used
- Uses type compatibility to validate expressions, constrain attribute values, and select type-specific rendering.
- How deep it goes
- Implements equality-based matching and contrasts it with assignability, inheritance, and coercion without implementing those broader relations.
- Examples
- Demonstrates compatibility with amount, date range, percentage, untyped values, binary subtraction, attribute assignments, and display markers.
- What you can do after
- Build it from scratch by representing types as objects, comparing stable IDs, and propagating checks into constraints and projections.
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Clojure: The Essential Reference
Type compatibility is the property that two values belong to categories that an operation can compare according to its compatibility rules.
- How it is used
- Compares Clojure values with diff while preserving compatible collection structure.
- How deep it goes
- Explains collection predicates, scalar equality, nested outputs, exceptions, and deep-recursion limits.
- Examples
- Uses vectors, lists, maps, sets, arrays, sorted maps, and deeply nested maps as comparison cases.
- What you can do after
- Diagnose compatible and incompatible comparisons by interpreting diff's unique and common result positions.
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Functional Programming in JavaScript
The property that one function’s output type matches another function’s accepted input type.
- How it is used
- Connects stages in functional pipelines by matching returned values with receiving function inputs.
- How deep it goes
- Defines output-input matching, explains duck typing in JavaScript, and stops short of covering static type systems.
- Examples
- Uses trim, normalize, and isValid to process a Social Security number through compatible function stages.
- What you can do after
- Apply it via function signatures to design pipelines whose stages accept one another’s outputs.
Read how Functional Programming in JavaScript explains type compatibility →
Related concepts
- subtypingmeasured by · Subtyping is a type-system relationship in which values of a more specific type can be used wherever a compatible, more general type is expected.
- assignment compatibilityuses · Assignment compatibility is a type-system relation determining whether a value or expression of one type can be assigned to an object of another type.
- type equalityequivalent to · A type equality is a constraint asserting that two type expressions must denote the same type.
- arityequivalent to · Arity is the number of arguments or operands accepted by a function, method, operator, or other operation.
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