1 Introduction

narrowed-types

Type definitions narrowed with predicates

Description

This Common Lisp package provides a single macro which helps you define type specifiers for subsets, on the basis on an existing supertype and a condition expressed on the value.

DEFMACRO deftype-narrowed ((var type super-type) &body body)

DEFTYPE-NARROWED defines a type with name TYPE as well as a matching predicate TYPE-p.
The instances of the resulting type are the subset of instances of SUPER-TYPE which satisfy
a condition on VAR expressed by the BODY of the statement.

Example

This simple example defines a type for the odd integers.

(deftype-narrowed (x odd-integer integer)
  (oddp x))

Note: In the body of the example, the argument x to oddp is guaranteed to be an instance of the supertype integer.

The type odd-integer is usable in any context where a type specifier is expected. This includes standard forms such as typep, check-type, typecase, the, defstruct, defclass. You may not use it however to specialize a generic method.

(typecase x
  (odd-integer :odd)
  (integer :even)
  (t :other))

For some more usage examples, see tests.

References

CLHS 4.2.3: Type Specifiers

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2 Systems

The main system appears first, followed by any subsystem dependency.

• narrowed-types

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3 Files

Files are sorted by type and then listed depth-first from the systems components trees.

• Lisp

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4 Packages

Packages are listed by definition order.

• narrowed-types

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5 Definitions

Definitions are sorted by export status, category, package, and then by lexicographic order.

• Public Interface

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