;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.
-(in-package "SB!EXT")
+(in-package "SB!IMPL")
-;;; Lots of code wants to get to the KEYWORD package or the COMMON-LISP package
-;;; without a lot of fuss, so we cache them in variables. TO DO: How much
-;;; does this actually buy us? It sounds sensible, but I don't know for sure
-;;; that it saves space or time.. -- WHN 19990521
+;;; Lots of code wants to get to the KEYWORD package or the
+;;; COMMON-LISP package without a lot of fuss, so we cache them in
+;;; variables. TO DO: How much does this actually buy us? It sounds
+;;; sensible, but I don't know for sure that it saves space or time..
+;;; -- WHN 19990521
+;;;
+;;; (The initialization forms here only matter on the cross-compilation
+;;; host; In the target SBCL, these variables are set in cold init.)
(declaim (type package *cl-package* *keyword-package*))
-(defvar *cl-package* (find-package "COMMON-LISP"))
-(defvar *keyword-package* (find-package "KEYWORD"))
+(defvar *cl-package* (find-package "COMMON-LISP"))
+(defvar *keyword-package* (find-package "KEYWORD"))
+
+;;; a helper function for various macros which expect clauses of a
+;;; given length, etc.
+;;;
+;;; FIXME: This implementation will hang on circular list structure.
+;;; Since this is an error-checking utility, i.e. its job is to deal
+;;; with screwed-up input, it'd be good style to fix it so that it can
+;;; deal with circular list structure.
+(eval-when (:compile-toplevel :load-toplevel :execute)
+ ;; Return true if X is a proper list whose length is between MIN and
+ ;; MAX (inclusive).
+ (defun proper-list-of-length-p (x min &optional (max min))
+ (cond ((minusp max)
+ nil)
+ ((null x)
+ (zerop min))
+ ((consp x)
+ (and (plusp max)
+ (proper-list-of-length-p (cdr x)
+ (if (plusp (1- min))
+ (1- min)
+ 0)
+ (1- max))))
+ (t nil))))
\f
;;;; the COLLECT macro
-;;; helper functions for COLLECT, which become the expanders of the MACROLET
-;;; definitions created by COLLECT
+;;; helper functions for COLLECT, which become the expanders of the
+;;; MACROLET definitions created by COLLECT
;;;
;;; COLLECT-NORMAL-EXPANDER handles normal collection macros.
;;;
macros))))
`(macrolet ,macros (let* ,(nreverse binds) ,@body))))
\f
+;;; This function can be used as the default value for keyword
+;;; arguments that must be always be supplied. Since it is known by
+;;; the compiler to never return, it will avoid any compile-time type
+;;; warnings that would result from a default value inconsistent with
+;;; the declared type. When this function is called, it signals an
+;;; error indicating that a required &KEY argument was not supplied.
+;;; This function is also useful for DEFSTRUCT slot defaults
+;;; corresponding to required arguments.
(declaim (ftype (function () nil) required-argument))
(defun required-argument ()
#!+sb-doc
- "This function can be used as the default value for keyword arguments that
- must be always be supplied. Since it is known by the compiler to never
- return, it will avoid any compile-time type warnings that would result from a
- default value inconsistent with the declared type. When this function is
- called, it signals an error indicating that a required keyword argument was
- not supplied. This function is also useful for DEFSTRUCT slot defaults
- corresponding to required arguments."
(/show0 "entering REQUIRED-ARGUMENT")
- (error "A required keyword argument was not supplied."))
+ (error "A required &KEY argument was not supplied."))
\f
-;;; "the ultimate iteration macro"
+;;; "the ultimate iteration macro"
;;;
;;; note for Schemers: This seems to be identical to Scheme's "named LET".
-(defmacro iterate (name binds &body body)
+(defmacro named-let (name binds &body body)
#!+sb-doc
- "Iterate Name ({(Var Initial-Value)}*) Declaration* Form*
- This is syntactic sugar for Labels. It creates a local function Name with
- the specified Vars as its arguments and the Declarations and Forms as its
- body. This function is then called with the Initial-Values, and the result
- of the call is returned from the macro."
(dolist (x binds)
(unless (proper-list-of-length-p x 2)
(error "Malformed ITERATE variable spec: ~S." x)))
`(labels ((,name ,(mapcar #'first binds) ,@body))
(,name ,@(mapcar #'second binds))))
-\f
-;;; Once-Only is a utility useful in writing source transforms and macros.
-;;; It provides an easy way to wrap a LET around some code to ensure that some
-;;; forms are only evaluated once.
+
+;;; ONCE-ONLY is a utility useful in writing source transforms and
+;;; macros. It provides a concise way to wrap a LET around some code
+;;; to ensure that some forms are only evaluated once.
+;;;
+;;; Create a LET* which evaluates each value expression, binding a
+;;; temporary variable to the result, and wrapping the LET* around the
+;;; result of the evaluation of BODY. Within the body, each VAR is
+;;; bound to the corresponding temporary variable.
(defmacro once-only (specs &body body)
- #!+sb-doc
- "Once-Only ({(Var Value-Expression)}*) Form*
- Create a Let* which evaluates each Value-Expression, binding a temporary
- variable to the result, and wrapping the Let* around the result of the
- evaluation of Body. Within the body, each Var is bound to the corresponding
- temporary variable."
- (iterate frob
- ((specs specs)
- (body body))
+ (named-let frob ((specs specs)
+ (body body))
(if (null specs)
`(progn ,@body)
(let ((spec (first specs)))
(let* ((name (first spec))
(exp-temp (gensym (symbol-name name))))
`(let ((,exp-temp ,(second spec))
- (,name (gensym "OO-")))
+ (,name (gensym "ONCE-ONLY-")))
`(let ((,,name ,,exp-temp))
,,(frob (rest specs) body))))))))
\f
;; which is pretty, but which would have required adding awkward
;; build order constraints on SBCL (or figuring out some way to make
;; inline definitions installable at build-the-cross-compiler time,
- ;; which was too ambitious for now). Rather than mess with that,
- ;; we just define ASSQ explicitly in terms of more primitive operations:
+ ;; which was too ambitious for now). Rather than mess with that, we
+ ;; just define ASSQ explicitly in terms of more primitive
+ ;; operations:
(dolist (pair alist)
(when (eq (car pair) item)
(return pair))))
(setq list (cdr x))
(rplacd splice (cdr x))))
(t (setq splice x)))))) ; Move splice along to include element.
+
+
+;; (defmacro posq (item list) `(position ,item ,list :test #'eq))
+(defun posq (item list)
+ #!+sb-doc
+ "Returns the position of the first element EQ to ITEM."
+ (do ((i list (cdr i))
+ (j 0 (1+ j)))
+ ((null i))
+ (when (eq (car i) item)
+ (return j))))
+
+;; (defmacro neq (x y) `(not (eq ,x ,y)))
+(defun neq (x y) (not (eq x y)))
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