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Add #'constantly, as specified by ANSI Common Lisp. 2010-02-22 Aidan Kehoe <kehoea@parhasard.net> * cl-extra.el (constantly): Add this function, from ANSI Common Lisp, using the SBCL extension that extra arguments to it are passed back as multiple values in the constructed function. * cl-macs.el (constantly): In the compiler macro for #'constantly, construct a compiled-function object almost every time, at compile time when all arguments are constant, and at runtime when they vary.
author Aidan Kehoe <kehoea@parhasard.net>
date Mon, 22 Feb 2010 20:08:51 +0000
parents 8800b5350a13
children 868a9ffcc37b
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5036:9624523604c5 5056:6aba0daedb7c
610 (cond ((atom (cdr plst)) 610 (cond ((atom (cdr plst))
611 (error "Malformed property list: %S." plist)) 611 (error "Malformed property list: %S." plist))
612 ((memq (car plst) indicator-list) 612 ((memq (car plst) indicator-list)
613 (return (values (car plst) (cadr plst) plst)))))) 613 (return (values (car plst) (cadr plst) plst))))))
614 614
615 ;; See our compiler macro in cl-macs.el, we will only pass back the
616 ;; actual lambda list in interpreted code or if we've been funcalled
617 ;; (from #'apply or #'mapcar or whatever).
618 (defun constantly (value &rest more-values)
619 "Construct a function always returning VALUE, and possibly MORE-VALUES.
620
621 The constructed function accepts any number of arguments, and ignores them.
622
623 Members of MORE-VALUES, if provided, will be passed as multiple values; see
624 `multiple-value-bind' and `multiple-value-setq'."
625 `(lambda (&rest ignore) (values-list ',(cons value more-values))))
615 626
616 ;;; Hash tables. 627 ;;; Hash tables.
617 628
618 ;; The `regular' Common Lisp hash-table stuff has been moved into C. 629 ;; The `regular' Common Lisp hash-table stuff has been moved into C.
619 ;; Only backward compatibility stuff remains here. 630 ;; Only backward compatibility stuff remains here.