Burke_et_al-NIL_Reference_Manual_0286-1984

Prcdic4Jtes 16 Nil. Mamml
4. Predicates
4.1 Type Predicates
4. J.I Type Specifiers
A type specifier is an expression which may be used to exprcs.~ a data-type constraint.
nil No object is of the type nit: nif is a subtype of aU types.
t All objects arc of the type 1. For· instctncc.
(make-array ·(10 10) :.element-type t)
m~tkcs an 10xl0 ~lrmy which can huld objects of any type.
tJt,c-name
This is the most common fhnn of type specifier; just a type name. filr insumcc number.
double-float. string. IJ1'('-llilmemay be .the name of 1 flavor defined with defflavor
(page 173). the name of a stnJcture defined by defstruct {page 125) (assuming defstruct
is not told to implement the stnlcturc in some other fashion). or one of the m,my NIL
types noted in various places in this document
(not type-specijiery
AU objects which are not of type type-specifier.
Carto !s! !s2 ... IS!?)
The intersection of the types corresponding to the given type spccifiers~
(or lsi Is) •.. tsn)
The union of the types corresponding to the given type sp~jfiers.
(member x) xl ... XIl)
This describes a type which is one of the objects xl, xl, ... xiz. Equality is defined by
eql (page 20).
(satisfiesjUnclion-name)
An object is a ttmember" of this type if junction-name returns a non-null value when
applied to it, otherwise it is not.
. There are some more complex fonns which are used variously as synonyms for, and
constraints on. more general types. For instance:
(integer low high)
An object is of this type if it is an integer between low and high. low and high may be
integers. in which case the boundary check is illclusive, lists of integers. in which case the
boundary check is exclusive. or the atom ., which signifies infinity of the appropriate
sign. Thus. (integer 0 .) is a type specifier for all non-negative integers. and (integer
(0) .) or (integer 1 .) for all positive integers.
(signed - byte size)
(unsigned - byte size)
An object is of these types if it can be r.cprcscnted in the appropriate fonn in twos-
MC:NILMAN:PRElJ 29
23-DEC-83
, .. ~ , - ~
-,.:,:c ".,~> .. ); ". }': ..', J'-. : : " ',' ~
,
,.... .' ,". . ~.
,