ANSI Common Lisp 3 Evaluation and Compilation 3.8 Dictionary Evaluation and Compilation
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 the next figure.
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.
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
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
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.)
- Exceptional Situations:
The consequences of trying to use a declare expression as
a form to be evaluated are undefined.
- See Also:
Section 4.2.3 Type Specifiers,
- Allegro CL Implementation Details: