Symbol declare

Syntax:

Arguments:

9.1.0 6declaration-specifier—a declaration specifier; not evaluated.

Description:

9.1.0 2A 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.

Deleted GENERIC-FLET, GENERIC-LABELS, GENERIC-FUNCTION -kmp 7-Feb-92 Deleted WITH-ADDED-METHODS. -kmp 7-Jan-91 Added DEFINE-COMPILER-MACRO, DESTRUCTURING-BIND, HANDLER-CASE, PPRINT-LOGICAL-BLOCK, RESTART-CASE, WITH-HASH-TABLE-ITERATOR, and WITH-PACKAGE-ITERATOR. -kmp 15-Feb-92

A declare expression can only occur where specified by the syntax of these forms. 9.1.0 3The 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.”

This doesn't belong here. I think it is adequately covered by the discussion of lambda lists and scoping of lambda variables. --sjl 5 mar 92 When evaluating a \term{lambda form}, none of the \term{bound declarations} made by \misc{declare} \term{expressions} appearing at the beginning of the body of the \term{lambda expression} apply to the \term{argument} \term{evaluations}. However, such \term{declarations} apply to the \term{initialization form} code (if any) for \keyref{optional}, \keyref{key}, and \keyref{aux} \term{bindings} Added to please KMP (and hopefully Moon, too). subsequent to the \term{name} to which the \term{bound declaration} refers; \seesection\DeclScope.

\term{macro} calls may expand into declarations as long as this syntax is observed.Macro forms cannot expand into declarations; declare expressions must appear as actual subexpressions of the form to which they refer. the only valid declarations are \term{lists} whose \term{car} is the symbol \misc{declare}. Removed because this is already said in PROCLAIM. \term{Macro forms} can expand into \funref{proclaim} forms, however.

The next figure shows a list of declaration identifiers that can be used with declare.

function removed.

9.2.0 20An 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 Added for Moon: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.

Editor: KMP: Probably we need to say something here about ill-formed declare expressions.

See Also:

proclaim, Section 4.2.3 (Type Specifiers), declaration, dynamic-extent, ftype, ignorable, ignore, inline, notinline, optimize, type

Notes:

None.