How deeply does Building User-Friendly DSLs cover type compatibility?

Implements equality-based matching and contrasts it with assignability, inheritance, and coercion without implementing those broader relations.

Type compatibility

As explained in Building User-Friendly DSLs

A relation between types specifying whether values of one type can be used where values of another type are expected.

Type compatibility determines whether a value of one type may be used where another type is expected. A simple type system can define compatibility as equality: two type objects match when their IDs match. Practical systems often use directional assignability instead, where type T is assignable to type U without requiring the reverse. section 13.3

Implementation uses compatibility to:

Compare type objects by stable IDs rather than JavaScript object identity. section 13.3

How Building User-Friendly DSLs covers it

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Also explained in

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Clojure: The Essential ReferenceType compatibility is the property that two values belong to categories that an operation can compare according to its compatibility rules.
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Functional Programming in JavaScriptThe property that one function’s output type matches another function’s accepted input type.

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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.

This explainer was generated by Manning's knowledge graph from the text of Building User-Friendly DSLs. The section links point to the parts of the book it draws on.