Syntax:
declare declaration-specifier*
Arguments:
declaration-specifier---a declaration specifier; not evaluated.
Description:
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 the next figure.
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.
The next figure 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.
Examples:
(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.)
Affected By: None.
Exceptional Situations:
The consequences of trying to use a declare expression as a form to be evaluated are undefined.
See Also:
proclaim, Section 4.2.3 (Type Specifiers), declaration, dynamic-extent, ftype, ignorable, ignore, inline, notinline, optimize, type
Notes: None.