Next: ignore, Previous: declaim, Up: Evaluation and Compilation Dictionary
declare {declaration-specifier}*
declaration-specifier—a declaration specifier; not evaluated.
A declare expression, sometimes called a declaration, can occur only at the beginning of the bodies of certain forms; that is, it may be preceded only by other declare expressions, or by a documentation string if the context permits.
A declare expression can occur in a lambda expression or in any of the forms listed in Figure 3–23.
defgeneric do-external-symbols prog
define-compiler-macro do-symbols prog*
define-method-combination dolist restart-case
define-setf-expander dotimes symbol-macrolet
defmacro flet with-accessors
defmethod handler-case with-hash-table-iterator
defsetf labels with-input-from-string
deftype let with-open-file
defun let* with-open-stream
destructuring-bind locally with-output-to-string
do macrolet with-package-iterator
do* multiple-value-bind with-slots
do-all-symbols pprint-logical-block
Figure 3–23: Standardized Forms In Which Declarations Can Occur
A declare expression can only occur where specified by the syntax of these forms. The consequences of attempting to evaluate a declare expression are undefined. In situations where such expressions can appear, explicit checks are made for their presence and they are never actually evaluated; it is for this reason that they are called “declare expressions” rather than “declare forms.”
Macro forms cannot expand into declarations; declare expressions must appear as actual subexpressions of the form to which they refer.
Figure 3–24 shows a list of declaration identifiers that can be used with declare.
dynamic-extent ignore optimize ftype inline special ignorable notinline type Figure 3–24: Local Declaration Specifiers
An implementation is free to support other (implementation-defined) declaration identifiers as well.
(defun nonsense (k x z)
(foo z x) ;First call to foo
(let ((j (foo k x)) ;Second call to foo
(x (* k k)))
(declare (inline foo) (special x z))
(foo x j z))) ;Third call to foo
In this example, the inline declaration applies only to the third call to foo, but not to the first or second ones. The special declaration of x causes let to make a dynamic binding for x, and causes the reference to x in the body of let to be a dynamic reference. The reference to x in the second call to foo is a local reference to the second parameter of nonsense. The reference to x in the first call to foo is a local reference, not a special one. The special declaration of z causes the reference to z in the third call to foo to be a dynamic reference; it does not refer to the parameter to nonsense named z, because that parameter binding has not been declared to be special. (The special declaration of z does not appear in the body of defun, but in an inner form, and therefore does not affect the binding of the parameter.)
The consequences of trying to use a declare expression as a form to be evaluated are undefined.
[Editorial Note by KMP: Probably we need to say something here about ill-formed declare expressions.]
proclaim , Type Specifiers, declaration, dynamic-extent, ftype, ignorable, ignore, inline, notinline, optimize, type
Next: ignore, Previous: declaim, Up: Evaluation and Compilation Dictionary