(define fluid-$@  (make-preserved-thread-fluid (list)))
(define fluid-$<  (make-preserved-thread-fluid (list)))
(define fluid-$?  (make-preserved-thread-fluid (list)))
(define fluid-$^  (make-preserved-thread-fluid (list)))
(define fluid-$+  (make-preserved-thread-fluid (list)))
(define fluid-$*  (make-preserved-thread-fluid (list)))
(define fluid-$@/ (make-preserved-thread-fluid (list)))
(define fluid-/$@ (make-preserved-thread-fluid (list)))
(define fluid-$*/ (make-preserved-thread-fluid (list)))
(define fluid-/$* (make-preserved-thread-fluid (list)))
(define fluid-$</ (make-preserved-thread-fluid (list)))
(define fluid-/$< (make-preserved-thread-fluid (list)))
(define fluid-$^/ (make-preserved-thread-fluid (list)))
(define fluid-/$^ (make-preserved-thread-fluid (list)))
(define fluid-$+/ (make-preserved-thread-fluid (list)))
(define fluid-/$+ (make-preserved-thread-fluid (list)))
(define fluid-$?/ (make-preserved-thread-fluid (list)))
(define fluid-/$? (make-preserved-thread-fluid (list)))

(define (bind-fluids-gnu target prereqs prereqs-results thunk)
  (let (($@ target)
	($< (cond 
	     ((and (list? prereqs) (not (null? prereqs))) (car prereqs))
	     ((and (list? prereqs) (null? prereqs)) "")
	     (else prereqs)))
	($? (cond 
	     ((not (list? prereqs)) 
	      (let ((newer-prereq (list)))
		(if (car (rule-result-wants-build? 
			  (car prereqs-results)))
		    (cons newer-prereq newer-prereq)
		    newer-prereq)))
	     ((and (list? prereqs) (null? prereqs)) prereqs)
	     ((list? prereqs)
	      (let for-prereqs ((newer-prereqs (list))
				(current-prereq (car prereqs))
				(todo-prereqs (cdr prereqs))
				(current-result (car prereqs-results))
				(todo-results (cdr prereqs-results)))
		(let ((build? (if (is-rule-result? current-result)
				  (car (rule-result-wants-build?
					current-result))
				  #f)))
		  (if build?
		      (if (not (null? todo-prereqs))
			  (for-prereqs (cons current-prereq 
					     newer-prereqs)
				       (car todo-prereqs) 
				       (cdr todo-prereqs)
				       (car todo-results) 
				       (cdr todo-results))
			  newer-prereqs)
		      (if (not (null? todo-prereqs))
			  (for-prereqs newer-prereqs
				       (car todo-prereqs) 
				       (cdr todo-prereqs)
				       (car todo-results) 
				       (cdr todo-results))
			  newer-prereqs)))))
	     (else (error "no match in bind-fluids-gnu fluid-$?"))))
	($^ (delete-duplicates! prereqs))
	($+ prereqs)
	($* ""))

    (let-thread-fluids fluid-$@ $@ ;; $@ : file name of the target
		       ;; $% : target member name, when target is an archive member.
		       ;; fluid-$% target
		       
		       ;; $< : name of the first prerequisite
		       fluid-$< $<
		       
		       ;; $? : names of all prerequisites that are newer than target
		       fluid-$? $?

		       ;; $^ : names of all the prerequisites without duplicates 
		       ;; $+ : names of all the prerequisites
		       fluid-$^ $^
		       fluid-$+ $+

		       ;; $* : The stem with which an implicit rule matches.
		       fluid-$* $*
	      
		       ;; we have no parens so we will use the following *scheme*:
		       ;; e.g. for $@: $@/ denotes directory part of $@
		       ;; while        /$@ denotes file within directory of $@
		       ;;
		       ;; $(@D), $(@F) : directory part and file-within-directory
		       fluid-$@/ (file-name-directory $@)
		       fluid-/$@ (file-name-nondirectory $@)

		       ;; $(*D), $(*F) : directory part and file-within-directory
		       fluid-$*/ (file-name-directory $*)
		       fluid-/$* (file-name-nondirectory $*)

		       ;; $(%D), $(%F) : directory part and file-within-directory
;	$%/ (file-name-directory fluid-$%)
;	/$% (file-name-nondirectory fluid-$%)
	
		       ;; $(<D), $(<F) : directory part and file-within-directory
		       fluid-$</ (file-name-directory $<)
		       fluid-/$< (file-name-nondirectory $<)

		       ;; $(^D), $(^F) : directory part and file-within-directory
		       fluid-$^/ (map (lambda (d) 
					(file-name-directory d))
				      $^)
		       fluid-/$^ (map (lambda (f) 
					(file-name-nondirectory f))
				      $^)
	      
		     ;; $(+D), $(+F) : directory part and file-within-directory
		       fluid-$+/ (map (lambda (d) 
					(file-name-directory d))
				      $+)
		       fluid-/$+ (map (lambda (f) 
					(file-name-nondirectory f))
				      $+)
	      
		       ;; $(?D), $(?F) : directory part and the
		       ;;                file-within-directory part of $?.
		       fluid-$?/ (map (lambda (d) 
					(file-name-directory d))
				      $?)
		       fluid-/$? (map (lambda (f) 
					(file-name-nondirectory f))
				      $?)
		       thunk)))

(define ($@)  (thread-fluid fluid-$@))
(define ($<)  (thread-fluid fluid-$<))
(define ($?)  (thread-fluid fluid-$?))
(define ($^)  (thread-fluid fluid-$^))
(define ($+)  (thread-fluid fluid-$+))
(define ($*)  (thread-fluid fluid-$*))
(define ($@/) (thread-fluid fluid-$@/))
(define (/$@) (thread-fluid fluid-/$@))
(define ($*/) (thread-fluid fluid-$*/))
(define (/$*) (thread-fluid fluid-/$*))
(define ($</) (thread-fluid fluid-$</))
(define (/$<) (thread-fluid fluid-/$<))
(define ($^/) (thread-fluid fluid-$^/))
(define (/$^) (thread-fluid fluid-/$^))
(define ($+/) (thread-fluid fluid-$+/))
(define (/$+) (thread-fluid fluid-/$+))
(define ($?/) (thread-fluid fluid-$?/))
(define (/$?) (thread-fluid fluid-/$?))

(define (bind-fluids-human target prereqs prereqs-results thunk)
  (display "not yet implemented."))

;;; (define (bind-fluids-human target prereqs prereqs-results thunk)
;;;   (lambda () 
;;;     (bind-fluids-gnu target prereqs prereqs-results
;;; 		     (lambda () 
;;; 		       (let ((target-fname (make-preserved-thread-fluid $@))
;;; 			     (prereqs-first (make-preserved-thread-fluid $<))
;;; 			     (prereqs-to-build (make-preserved-thread-fluid $?))
;;; 			     (prereqs-unique (make-preserved-thread-fluid $^))
;;; 			     (prereqs (make-preserved-thread-fluid $+)))
;;; 			 (thunk))))))