"Like `case2', but signals an error if no clause matches the SCRUTINEE."
(do-case2-like 'ecase vform clauses))
-;;;--------------------------------------------------------------------------
-;;; Locatives.
-
-(export '(loc locp))
-(defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
- "Locative data type. See `locf' and `ref'."
- (reader nil :type function)
- (writer nil :type function))
-
-(export 'locf)
-(defmacro locf (place &environment env)
- "Slightly cheesy locatives.
-
- (locf PLACE) returns an object which, using the `ref' function, can be
- used to read or set the value of PLACE. It's cheesy because it uses
- closures rather than actually taking the address of something. Also,
- unlike Zetalisp, we don't overload `car' to do our dirty work."
- (multiple-value-bind
- (valtmps valforms newtmps setform getform)
- (get-setf-expansion place env)
- `(let* (,@(mapcar #'list valtmps valforms))
- (make-loc (lambda () ,getform)
- (lambda (,@newtmps) ,setform)))))
-
-(export 'ref)
-(declaim (inline ref (setf ref)))
-(defun ref (loc)
- "Fetch the value referred to by a locative."
- (funcall (loc-reader loc)))
-(defun (setf ref) (new loc)
- "Store a new value in the place referred to by a locative."
- (funcall (loc-writer loc) new))
-
-(export 'with-locatives)
-(defmacro with-locatives (locs &body body)
- "Evaluate BODY with implicit locatives.
-
- LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
- symbol and LOC-EXPR evaluates to a locative. If LOC-EXPR is omitted, it
- defaults to SYM. As an abbreviation for a common case, LOCS may be a
- symbol instead of a list.
-
- The BODY is evaluated in an environment where each SYM is a symbol macro
- which expands to (ref LOC-EXPR) -- or, in fact, something similar which
- doesn't break if LOC-EXPR has side-effects. Thus, references, including
- `setf' forms, fetch or modify the thing referred to by the LOC-EXPR.
- Useful for covering over where something uses a locative."
- (setf locs (mapcar (lambda (item)
- (cond ((atom item) (list item item))
- ((null (cdr item)) (list (car item) (car item)))
- (t item)))
- (if (listp locs) locs (list locs))))
- (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs))
- (ll (mapcar #'cadr locs))
- (ss (mapcar #'car locs)))
- `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll))
- (symbol-macrolet (,@(mapcar (lambda (sym tmp)
- `(,sym (ref ,tmp))) ss tt))
- ,@body))))
-
;;;--------------------------------------------------------------------------
;;; Standard error-reporting functions.