CLHS: Function TYPE-OF

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Function TYPE-OF

Syntax:

type-of object => typespec

Arguments and Values:

object---an object.

typespec---a type specifier.

Description:

Returns a type specifier, typespec, for a type that has the object as an element. The typespec satisfies the following:

1. For any object that is an element of some built-in type:

  a. the type returned is a recognizable subtype of that built-in type.

  b. the type returned does not involve `and`, `eql`, `member`, `not`, `or`, `satisfies`, or `values`.

2. For all objects, `(typep` object`(type-of` object`))` returns true. Implicit in this is that type specifiers which are not valid for use with typep, such as the list form of the function type specifier, are never returned by type-of.

3. The type returned by type-of is always a recognizable subtype of the class returned by class-of. That is,

       (subtypep (type-of object) (class-of object)) =>  true, true

4. For objects of metaclass structure-class or standard-class, and for conditions, type-of returns the proper name of the class returned by class-of if it has a proper name, and otherwise returns the class itself. In particular, for objects created by the constructor function of a structure defined with defstruct without a `:type` option, type-of returns the structure name; and for objects created by make-condition, the typespec is the name of the condition type.

5. For each of the types short-float, single-float, double-float, or long-float of which the object is an element, the typespec is a recognizable subtype of that type.

Examples:

     (type-of 'a) =>  SYMBOL
     (type-of '(1 . 2))
    =>  CONS
    OR=>  (CONS FIXNUM FIXNUM)
     (type-of #c(0 1))
    =>  COMPLEX
    OR=>  (COMPLEX INTEGER)
     (defstruct temp-struct x y z) =>  TEMP-STRUCT
     (type-of (make-temp-struct)) =>  TEMP-STRUCT
     (type-of "abc")
    =>  STRING
    OR=>  (STRING 3)
     (subtypep (type-of "abc") 'string) =>  true, true
     (type-of (expt 2 40))
    =>  BIGNUM
    OR=>  INTEGER
    OR=>  (INTEGER 1099511627776 1099511627776)
    OR=>  SYSTEM::TWO-WORD-BIGNUM
    OR=>  FIXNUM
     (subtypep (type-of 112312) 'integer) =>  true, true
     (defvar *foo* (make-array 5 :element-type t)) =>  *FOO*
     (class-name (class-of *foo*)) =>  VECTOR
     (type-of *foo*)
    =>  VECTOR
    OR=>  (VECTOR T 5)

Affected By: None.

Exceptional Situations: None.

See Also:

array-element-type, class-of, defstruct, typecase, typep, Section 4.2 (Types)

Notes:

Implementors are encouraged to arrange for type-of to return a portable value.

The following X3J13 cleanup issues, not part of the specification, apply to this section:

- TYPE-OF-AND-PREDEFINED-CLASSES:TYPE-OF-HANDLES-FLOATS
- TYPE-OF-AND-PREDEFINED-CLASSES:UNIFY-AND-EXTEND
- TYPE-OF-UNDERCONSTRAINED:ADD-CONSTRAINTS

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