Import Upstream version 2a6upstream/2a6

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+;;; "format.scm" Common LISP text output formatter for SLIB
+; Written 1992-1994 by Dirk Lutzebaeck (lutzeb@cs.tu-berlin.de)
+;
+; This code is in the public domain.
+
+; Authors of the original version (< 1.4) were Ken Dickey and Aubrey Jaffer.
+; Please send error reports to the email address above.
+; For documentation see slib.texi and format.doc.
+; For testing load formatst.scm.
+;
+; Version 3.0
+
+(provide 'format)
+(require 'string-case)
+(require 'string-port)
+(require 'rev4-optional-procedures)
+
+;;; Configuration ------------------------------------------------------------
+
+(define format:symbol-case-conv #f)
+;; Symbols are converted by symbol->string so the case of the printed
+;; symbols is implementation dependent. format:symbol-case-conv is a
+;; one arg closure which is either #f (no conversion), string-upcase!,
+;; string-downcase! or string-capitalize!.
+
+(define format:iobj-case-conv #f)
+;; As format:symbol-case-conv but applies for the representation of
+;; implementation internal objects.
+
+(define format:expch #\E)
+;; The character prefixing the exponent value in ~e printing.
+
+(define format:floats (provided? 'inexact))
+;; Detects if the scheme system implements flonums (see at eof).
+
+(define format:complex-numbers (provided? 'complex))
+;; Detects if the scheme system implements complex numbers.
+
+(define format:radix-pref (char=? #\# (string-ref (number->string 8 8) 0)))
+;; Detects if number->string adds a radix prefix.
+
+(define format:ascii-non-printable-charnames
+  '#("nul" "soh" "stx" "etx" "eot" "enq" "ack" "bel"
+     "bs"  "ht"  "nl"  "vt"  "np"  "cr"  "so"  "si"
+     "dle" "dc1" "dc2" "dc3" "dc4" "nak" "syn" "etb"
+     "can" "em"  "sub" "esc" "fs"  "gs"  "rs"  "us" "space"))
+
+;;; End of configuration ----------------------------------------------------
+
+(define format:version "3.0")
+(define format:port #f)			; curr. format output port
+(define format:output-col 0)		; curr. format output tty column
+(define format:flush-output #f)		; flush output at end of formatting
+(define format:case-conversion #f)
+(define format:error-continuation #f)
+(define format:args #f)
+(define format:pos 0)			; curr. format string parsing position
+(define format:arg-pos 0)		; curr. format argument position
+					; this is global for error presentation
+
+; format string and char output routines on format:port
+
+(define (format:out-str str)
+  (if format:case-conversion
+      (display (format:case-conversion str) format:port)
+      (display str format:port))
+  (set! format:output-col
+	(+ format:output-col (string-length str))))
+
+(define (format:out-char ch)
+  (if format:case-conversion
+      (display (format:case-conversion (string ch)) format:port)
+      (write-char ch format:port))
+  (set! format:output-col
+	(if (char=? ch #\newline)
+	    0
+	    (+ format:output-col 1))))
+
+;(define (format:out-substr str i n)  ; this allocates a new string
+;  (display (substring str i n) format:port)
+;  (set! format:output-col (+ format:output-col n)))
+
+(define (format:out-substr str i n)
+  (do ((k i (+ k 1)))
+      ((= k n))
+    (write-char (string-ref str k) format:port))
+  (set! format:output-col (+ format:output-col n)))
+
+;(define (format:out-fill n ch)       ; this allocates a new string
+;  (format:out-str (make-string n ch)))
+
+(define (format:out-fill n ch)
+  (do ((i 0 (+ i 1)))
+      ((= i n))
+    (write-char ch format:port))
+  (set! format:output-col (+ format:output-col n)))
+
+; format's user error handler
+
+(define (format:error . args)		; never returns!
+  (let ((error-continuation format:error-continuation)
+	(format-args format:args)
+	(port (current-error-port)))
+    (set! format:error format:intern-error)
+    (if (and (>= (length format:args) 2)
+	     (string? (cadr format:args)))
+	(let ((format-string (cadr format-args)))
+	  (if (not (zero? format:arg-pos))
+	      (set! format:arg-pos (- format:arg-pos 1)))
+	  (format port "~%FORMAT: error with call: (format ~a \"~a<===~a\" ~
+                                  ~{~a ~}===>~{~a ~})~%        "
+		  (car format:args)
+		  (substring format-string 0 format:pos)
+		  (substring format-string format:pos
+			     (string-length format-string))
+		  (list-head (cddr format:args) format:arg-pos)
+		  (list-tail (cddr format:args) format:arg-pos)))
+	(format port 
+		"~%FORMAT: error with call: (format~{ ~a~})~%        "
+		format:args))
+    (apply format port args)
+    (newline port)
+    (set! format:error format:error-save)
+    (set! format:error-continuation error-continuation)
+    (format:abort)
+    (format:intern-error "format:abort does not jump to toplevel!")))
+
+(define format:error-save format:error)
+
+(define (format:intern-error . args)   ;if something goes wrong in format:error
+  (display "FORMAT: INTERNAL ERROR IN FORMAT:ERROR!") (newline)
+  (display "        format args: ") (write format:args) (newline)
+  (display "        error args:  ") (write args) (newline)
+  (set! format:error format:error-save)
+  (format:abort))
+
+(define (format:format . args)		; the formatter entry
+  (set! format:args args)
+  (set! format:arg-pos 0)
+  (set! format:pos 0)
+  (if (< (length args) 1)
+      (format:error "not enough arguments"))
+  (let ((destination (car args))
+	(arglist (cdr args)))
+    (cond
+     ((or (and (boolean? destination)	; port output
+	       destination)
+	  (output-port? destination)
+	  (number? destination))
+      (format:out (cond
+		   ((boolean? destination) (current-output-port))
+		   ((output-port? destination) destination)
+		   ((number? destination) (current-error-port)))
+		  (car arglist) (cdr arglist)))
+     ((and (boolean? destination)	; string output
+	   (not destination))
+      (call-with-output-string
+       (lambda (port) (format:out port (car arglist) (cdr arglist)))))
+     ((string? destination)		; dest. is format string (Scheme->C)
+      (call-with-output-string
+       (lambda (port)
+	 (format:out port destination arglist))))
+     (else
+      (format:error "illegal destination `~a'" destination)))))
+
+(define (format:out port fmt args)	; the output handler for a port
+  (set! format:port port)		; global port for output routines
+  (set! format:case-conversion #f)	; modifier case conversion procedure
+  (set! format:flush-output #f)		; ~! reset
+  (let ((arg-pos (format:format-work fmt args))
+	(arg-len (length args)))
+    (cond
+     ((< arg-pos arg-len)
+      (set! format:arg-pos (+ arg-pos 1))
+      (set! format:pos (string-length fmt))
+      (format:error "~a superfluous argument~:p" (- arg-len arg-pos)))
+     ((> arg-pos arg-len)
+      (set! format:arg-pos (+ arg-len 1))
+      (display format:arg-pos)
+      (format:error "~a missing argument~:p" (- arg-pos arg-len)))
+     (else
+      (if format:flush-output (force-output port))
+      #t))))
+
+(define format:parameter-characters
+  '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\- #\+ #\v #\# #\'))
+
+(define (format:format-work format-string arglist) ; does the formatting work
+  (letrec
+      ((format-string-len (string-length format-string))
+       (arg-pos 0)			; argument position in arglist
+       (arg-len (length arglist))	; number of arguments
+       (modifier #f)			; 'colon | 'at | 'colon-at | #f
+       (params '())			; directive parameter list
+       (param-value-found #f)		; a directive parameter value found
+       (conditional-nest 0)		; conditional nesting level
+       (clause-pos 0)			; last cond. clause beginning char pos
+       (clause-default #f)		; conditional default clause string
+       (clauses '())			; conditional clause string list
+       (conditional-type #f)		; reflects the contional modifiers
+       (conditional-arg #f)		; argument to apply the conditional
+       (iteration-nest 0)		; iteration nesting level
+       (iteration-pos 0)		; iteration string beginning char pos
+       (iteration-type #f)		; reflects the iteration modifiers
+       (max-iterations #f)		; maximum number of iterations
+       (recursive-pos-save format:pos)
+
+       (next-char			; gets the next char from format-string
+	(lambda ()
+	  (let ((ch (peek-next-char)))
+	    (set! format:pos (+ 1 format:pos))
+	    ch)))
+
+       (peek-next-char
+	(lambda ()
+	  (if (>= format:pos format-string-len)
+	      (format:error "illegal format string")
+	      (string-ref format-string format:pos))))
+
+       (one-positive-integer?
+	(lambda (params)
+	  (cond
+	   ((null? params) #f)
+	   ((and (integer? (car params))
+		 (>= (car params) 0)
+		 (= (length params) 1)) #t)
+	   (else (format:error "one positive integer parameter expected")))))
+
+       (next-arg
+	(lambda ()
+	  (if (>= arg-pos arg-len)
+	      (begin
+		(set! format:arg-pos (+ arg-len 1))
+		(format:error "missing argument(s)")))
+	  (add-arg-pos 1)
+	  (list-ref arglist (- arg-pos 1))))
+
+       (prev-arg
+	(lambda ()
+	  (add-arg-pos -1)
+	  (if (negative? arg-pos)
+	      (format:error "missing backward argument(s)"))
+	  (list-ref arglist arg-pos)))
+
+       (rest-args
+	(lambda ()
+	  (let loop ((l arglist) (k arg-pos)) ; list-tail definition
+	    (if (= k 0) l (loop (cdr l) (- k 1))))))
+
+       (add-arg-pos
+	(lambda (n) 
+	  (set! arg-pos (+ n arg-pos))
+	  (set! format:arg-pos arg-pos)))
+
+       (anychar-dispatch		; dispatches the format-string
+	(lambda ()
+	  (if (>= format:pos format-string-len)
+	      arg-pos			; used for ~? continuance
+	      (let ((char (next-char)))
+		(cond
+		 ((char=? char #\~)
+		  (set! modifier #f)
+		  (set! params '())
+		  (set! param-value-found #f)
+		  (tilde-dispatch))
+		 (else
+		  (if (and (zero? conditional-nest)
+			   (zero? iteration-nest))
+		      (format:out-char char))
+		  (anychar-dispatch)))))))
+
+       (tilde-dispatch
+	(lambda ()
+	  (cond
+	   ((>= format:pos format-string-len)
+	    (format:out-str "~")	; tilde at end of string is just output
+	    arg-pos)			; used for ~? continuance
+	   ((and (or (zero? conditional-nest)
+		     (memv (peek-next-char) ; find conditional directives
+			   (append '(#\[ #\] #\; #\: #\@ #\^)
+				   format:parameter-characters)))
+		 (or (zero? iteration-nest)
+		     (memv (peek-next-char) ; find iteration directives
+			   (append '(#\{ #\} #\: #\@ #\^)
+				   format:parameter-characters))))
+	    (case (char-upcase (next-char))
+
+	      ;; format directives
+
+	      ((#\A)			; Any -- for humans
+	       (set! format:read-proof (memq modifier '(colon colon-at)))
+	       (format:out-obj-padded (memq modifier '(at colon-at))
+				      (next-arg) #f params)
+	       (anychar-dispatch))
+	      ((#\S)			; Slashified -- for parsers
+	       (set! format:read-proof (memq modifier '(colon colon-at)))
+	       (format:out-obj-padded (memq modifier '(at colon-at))
+				      (next-arg) #t params)
+	       (anychar-dispatch))
+	      ((#\D)			; Decimal
+	       (format:out-num-padded modifier (next-arg) params 10)
+	       (anychar-dispatch))
+	      ((#\X)			; Hexadecimal
+	       (format:out-num-padded modifier (next-arg) params 16)
+	       (anychar-dispatch))
+	      ((#\O)			; Octal
+	       (format:out-num-padded modifier (next-arg) params 8)
+	       (anychar-dispatch))
+	      ((#\B)			; Binary
+	       (format:out-num-padded modifier (next-arg) params 2)
+	       (anychar-dispatch))
+	      ((#\R)
+	       (if (null? params)
+		   (format:out-obj-padded ; Roman, cardinal, ordinal numerals
+		    #f
+		    ((case modifier
+		       ((at) format:num->roman)
+		       ((colon-at) format:num->old-roman)
+		       ((colon) format:num->ordinal)
+		       (else format:num->cardinal))
+		     (next-arg))
+		    #f params)
+		   (format:out-num-padded ; any Radix
+		    modifier (next-arg) (cdr params) (car params)))
+	       (anychar-dispatch))
+	      ((#\F)			; Fixed-format floating-point
+	       (if format:floats
+		   (format:out-fixed modifier (next-arg) params)
+		   (format:out-str (number->string (next-arg))))
+	       (anychar-dispatch))
+	      ((#\E)			; Exponential floating-point
+	       (if format:floats
+		   (format:out-expon modifier (next-arg) params)
+		   (format:out-str (number->string (next-arg))))
+	       (anychar-dispatch))
+	      ((#\G)			; General floating-point
+	       (if format:floats
+		   (format:out-general modifier (next-arg) params)
+		   (format:out-str (number->string (next-arg))))
+	       (anychar-dispatch))
+	      ((#\$)			; Dollars floating-point
+	       (if format:floats
+		   (format:out-dollar modifier (next-arg) params)
+		   (format:out-str (number->string (next-arg))))
+	       (anychar-dispatch))
+	      ((#\I)			; Complex numbers
+	       (if (not format:complex-numbers)
+		   (format:error
+		    "complex numbers not supported by this scheme system"))
+	       (let ((z (next-arg)))
+		 (if (not (complex? z))
+		     (format:error "argument not a complex number"))
+		 (format:out-fixed modifier (real-part z) params)
+		 (format:out-fixed 'at (imag-part z) params)
+		 (format:out-char #\i))
+	       (anychar-dispatch))
+	      ((#\C)			; Character
+	       (let ((ch (if (one-positive-integer? params)
+			     (integer->char (car params))
+			     (next-arg))))
+		 (if (not (char? ch)) (format:error "~~c expects a character"))
+		 (case modifier
+		   ((at)
+		    (format:out-str (format:char->str ch)))
+		   ((colon)
+		    (let ((c (char->integer ch)))
+		      (if (< c 0)
+			  (set! c (+ c 256))) ; compensate complement impl.
+		      (cond
+		       ((< c #x20)	; assumes that control chars are < #x20
+			(format:out-char #\^)
+			(format:out-char
+			 (integer->char (+ c #x40))))
+		       ((>= c #x7f)
+			(format:out-str "#\\")
+			(format:out-str
+			 (if format:radix-pref
+			     (let ((s (number->string c 8)))
+			       (substring s 2 (string-length s)))
+			     (number->string c 8))))
+		       (else
+			(format:out-char ch)))))
+		   (else (format:out-char ch))))
+	       (anychar-dispatch))
+	      ((#\P)			; Plural
+	       (if (memq modifier '(colon colon-at))
+		   (prev-arg))
+	       (let ((arg (next-arg)))
+		 (if (not (number? arg))
+		     (format:error "~~p expects a number argument"))
+		 (if (= arg 1)
+		     (if (memq modifier '(at colon-at))
+			 (format:out-char #\y))
+		     (if (memq modifier '(at colon-at))
+			 (format:out-str "ies")
+			 (format:out-char #\s))))
+	       (anychar-dispatch))
+	      ((#\~)			; Tilde
+	       (if (one-positive-integer? params)
+		   (format:out-fill (car params) #\~)
+		   (format:out-char #\~))
+	       (anychar-dispatch))
+	      ((#\%)			; Newline
+	       (if (one-positive-integer? params)
+		   (format:out-fill (car params) #\newline)
+		   (format:out-char #\newline))
+	       (set! format:output-col 0)
+	       (anychar-dispatch))
+	      ((#\&)			; Fresh line
+	       (if (one-positive-integer? params)
+		   (begin
+		     (if (> (car params) 0)
+			 (format:out-fill (- (car params)
+					     (if (> format:output-col 0) 0 1))
+					  #\newline))
+		     (set! format:output-col 0))
+		   (if (> format:output-col 0)
+		       (format:out-char #\newline)))
+	       (anychar-dispatch))
+	      ((#\_)			; Space character
+	       (if (one-positive-integer? params)
+		   (format:out-fill (car params) #\space)
+		   (format:out-char #\space))
+	       (anychar-dispatch))
+	      ((#\/)			; Tabulator character
+	       (if (one-positive-integer? params)
+		   (format:out-fill (car params) slib:tab)
+		   (format:out-char slib:tab))
+	       (anychar-dispatch))
+	      ((#\|)			; Page seperator
+	       (if (one-positive-integer? params)
+		   (format:out-str (car params) slib:form-feed)
+		   (format:out-char slib:form-feed))
+	       (set! format:output-col 0)
+	       (anychar-dispatch))
+	      ((#\T)			; Tabulate
+	       (format:tabulate modifier params)
+	       (anychar-dispatch))
+	      ((#\Y)			; Pretty-print
+	       (require 'pretty-print)
+	       (pretty-print (next-arg) format:port)
+	       (set! format:output-col 0)
+	       (anychar-dispatch))
+	      ((#\? #\K)		; Indirection (is "~K" in T-Scheme)
+	       (cond
+		((memq modifier '(colon colon-at))
+		 (format:error "illegal modifier in ~~?"))
+		((eq? modifier 'at)
+		 (let* ((frmt (next-arg))
+			(args (rest-args)))
+		   (add-arg-pos (format:format-work frmt args))))
+		(else
+		 (let* ((frmt (next-arg))
+			(args (next-arg)))
+		   (format:format-work frmt args))))
+	       (anychar-dispatch))
+	      ((#\!)			; Flush output
+	       (set! format:flush-output #t)
+	       (anychar-dispatch))
+	      ((#\newline)		; Continuation lines
+	       (if (eq? modifier 'at)
+		   (format:out-char #\newline))
+	       (if (< format:pos format-string-len)
+		   (do ((ch (peek-next-char) (peek-next-char)))
+		       ((or (not (char-whitespace? ch))
+			    (= format:pos (- format-string-len 1))))
+		     (if (eq? modifier 'colon)
+			 (format:out-char (next-char))
+			 (next-char))))
+	       (anychar-dispatch))
+	      ((#\*)			; Argument jumping
+	       (case modifier
+		 ((colon)		; jump backwards
+		  (if (one-positive-integer? params)
+		      (do ((i 0 (+ i 1)))
+			  ((= i (car params)))
+			(prev-arg))
+		      (prev-arg)))
+		 ((at)			; jump absolute
+		  (set! arg-pos (if (one-positive-integer? params)
+				    (car params) 0)))
+		 ((colon-at)
+		  (format:error "illegal modifier `:@' in ~~* directive"))
+		 (else			; jump forward
+		  (if (one-positive-integer? params)
+		      (do ((i 0 (+ i 1)))
+			  ((= i (car params)))
+			(next-arg))
+		      (next-arg))))
+	       (anychar-dispatch))
+	      ((#\()			; Case conversion begin
+	       (set! format:case-conversion
+		     (case modifier
+		       ((at) string-capitalize-first)
+		       ((colon) string-capitalize)
+		       ((colon-at) string-upcase)
+		       (else string-downcase)))
+	       (anychar-dispatch))
+	      ((#\))			; Case conversion end
+	       (if (not format:case-conversion)
+		   (format:error "missing ~~("))
+	       (set! format:case-conversion #f)
+	       (anychar-dispatch))
+	      ((#\[)			; Conditional begin
+	       (set! conditional-nest (+ conditional-nest 1))
+	       (cond
+		((= conditional-nest 1)
+		 (set! clause-pos format:pos)
+		 (set! clause-default #f)
+		 (set! clauses '())
+		 (set! conditional-type
+		       (case modifier
+			 ((at) 'if-then)
+			 ((colon) 'if-else-then)
+			 ((colon-at) (format:error "illegal modifier in ~~["))
+			 (else 'num-case)))
+		 (set! conditional-arg
+		       (if (one-positive-integer? params)
+			   (car params)
+			   (next-arg)))))
+	       (anychar-dispatch))
+	      ((#\;)                    ; Conditional separator
+	       (if (zero? conditional-nest)
+		   (format:error "~~; not in ~~[~~] conditional"))
+	       (if (not (null? params))
+		   (format:error "no parameter allowed in ~~;"))
+	       (if (= conditional-nest 1)
+		   (let ((clause-str
+			  (cond
+			   ((eq? modifier 'colon)
+			    (set! clause-default #t)
+			    (substring format-string clause-pos 
+				       (- format:pos 3)))
+			   ((memq modifier '(at colon-at))
+			    (format:error "illegal modifier in ~~;"))
+			   (else
+			    (substring format-string clause-pos
+				       (- format:pos 2))))))
+		     (set! clauses (append clauses (list clause-str)))
+		     (set! clause-pos format:pos)))
+	       (anychar-dispatch))
+	      ((#\])			; Conditional end
+	       (if (zero? conditional-nest) (format:error "missing ~~["))
+	       (set! conditional-nest (- conditional-nest 1))
+	       (if modifier
+		   (format:error "no modifier allowed in ~~]"))
+	       (if (not (null? params))
+		   (format:error "no parameter allowed in ~~]"))
+	       (cond
+		((zero? conditional-nest)
+		 (let ((clause-str (substring format-string clause-pos
+					      (- format:pos 2))))
+		   (if clause-default
+		       (set! clause-default clause-str)
+		       (set! clauses (append clauses (list clause-str)))))
+		 (case conditional-type
+		   ((if-then)
+		    (if conditional-arg
+			(format:format-work (car clauses)
+					    (list conditional-arg))))
+		   ((if-else-then)
+		    (add-arg-pos
+		     (format:format-work (if conditional-arg
+					     (cadr clauses)
+					     (car clauses))
+					 (rest-args))))
+		   ((num-case)
+		    (if (or (not (integer? conditional-arg))
+			    (< conditional-arg 0))
+			(format:error "argument not a positive integer"))
+		    (if (not (and (>= conditional-arg (length clauses))
+				  (not clause-default)))
+			(add-arg-pos
+			 (format:format-work
+			  (if (>= conditional-arg (length clauses))
+			      clause-default
+			      (list-ref clauses conditional-arg))
+			  (rest-args))))))))
+	       (anychar-dispatch))
+	      ((#\{)			; Iteration begin
+	       (set! iteration-nest (+ iteration-nest 1))
+	       (cond
+		((= iteration-nest 1)
+		 (set! iteration-pos format:pos)
+		 (set! iteration-type
+		       (case modifier
+			 ((at) 'rest-args)
+			 ((colon) 'sublists)
+			 ((colon-at) 'rest-sublists)
+			 (else 'list)))
+		 (set! max-iterations (if (one-positive-integer? params)
+					 (car params) #f))))
+	       (anychar-dispatch))
+	      ((#\})			; Iteration end
+	       (if (zero? iteration-nest) (format:error "missing ~~{"))
+	       (set! iteration-nest (- iteration-nest 1))
+	       (case modifier
+		 ((colon)
+		  (if (not max-iterations) (set! max-iterations 1)))
+		 ((colon-at at) (format:error "illegal modifier"))
+		 (else (if (not max-iterations) (set! max-iterations 100))))
+	       (if (not (null? params))
+		   (format:error "no parameters allowed in ~~}"))
+	       (if (zero? iteration-nest)
+		 (let ((iteration-str
+			(substring format-string iteration-pos
+				   (- format:pos (if modifier 3 2)))))
+		   (if (string=? iteration-str "")
+		       (set! iteration-str (next-arg)))
+		   (case iteration-type
+		     ((list)
+		      (let ((args (next-arg))
+			    (args-len 0))
+			(if (not (list? args))
+			    (format:error "expected a list argument"))
+			(set! args-len (length args))
+			(do ((arg-pos 0 (+ arg-pos
+					   (format:format-work
+					    iteration-str
+					    (list-tail args arg-pos))))
+			     (i 0 (+ i 1)))
+			    ((or (>= arg-pos args-len)
+				 (>= i max-iterations))))))
+		     ((sublists)
+		      (let ((args (next-arg))
+			    (args-len 0))
+			(if (not (list? args))
+			    (format:error "expected a list argument"))
+			(set! args-len (length args))
+			(do ((arg-pos 0 (+ arg-pos 1)))
+			    ((or (>= arg-pos args-len)
+				 (>= arg-pos max-iterations)))
+			  (let ((sublist (list-ref args arg-pos)))
+			    (if (not (list? sublist))
+				(format:error
+				 "expected a list of lists argument"))
+			    (format:format-work iteration-str sublist)))))
+		     ((rest-args)
+		      (let* ((args (rest-args))
+			     (args-len (length args))
+			     (usedup-args
+			      (do ((arg-pos 0 (+ arg-pos
+						 (format:format-work
+						  iteration-str
+						  (list-tail
+						   args arg-pos))))
+				   (i 0 (+ i 1)))
+				  ((or (>= arg-pos args-len)
+				       (>= i max-iterations))
+				   arg-pos))))
+			(add-arg-pos usedup-args)))
+		     ((rest-sublists)
+		      (let* ((args (rest-args))
+			     (args-len (length args))
+			     (usedup-args
+			      (do ((arg-pos 0 (+ arg-pos 1)))
+				  ((or (>= arg-pos args-len)
+				       (>= arg-pos max-iterations))
+				   arg-pos)
+				(let ((sublist (list-ref args arg-pos)))
+				  (if (not (list? sublist))
+				      (format:error "expected list arguments"))
+				  (format:format-work iteration-str sublist)))))
+			(add-arg-pos usedup-args)))
+		     (else (format:error "internal error in ~~}")))))
+	       (anychar-dispatch))
+	      ((#\^)			; Up and out
+	       (let* ((continue
+		       (cond
+			((not (null? params))
+			 (not
+			  (case (length params)
+			   ((1) (zero? (car params)))
+			   ((2) (= (list-ref params 0) (list-ref params 1)))
+			   ((3) (<= (list-ref params 0)
+				    (list-ref params 1)
+				    (list-ref params 2)))
+			   (else (format:error "too much parameters")))))
+			(format:case-conversion ; if conversion stop conversion
+			 (set! format:case-conversion string-copy) #t)
+			((= iteration-nest 1) #t)
+			((= conditional-nest 1) #t)
+			((>= arg-pos arg-len)
+			 (set! format:pos format-string-len) #f)
+			(else #t))))
+		 (if continue
+		     (anychar-dispatch))))
+
+	      ;; format directive modifiers and parameters
+
+	      ((#\@)			; `@' modifier
+	       (if (eq? modifier 'colon-at)
+		   (format:error "double `@' modifier"))
+	       (set! modifier (if (eq? modifier 'colon) 'colon-at 'at))
+	       (tilde-dispatch))
+	      ((#\:)			; `:' modifier
+	       (if modifier (format:error "illegal `:' modifier position"))
+	       (set! modifier 'colon)
+	       (tilde-dispatch))
+	      ((#\')			; Character parameter
+	       (if modifier (format:error "misplaced modifier"))
+	       (set! params (append params (list (char->integer (next-char)))))
+	       (set! param-value-found #t)
+	       (tilde-dispatch))
+	      ((#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\- #\+) ; num. paramtr
+	       (if modifier (format:error "misplaced modifier"))
+	       (let ((num-str-beg (- format:pos 1))
+		     (num-str-end format:pos))
+		 (do ((ch (peek-next-char) (peek-next-char)))
+		     ((not (char-numeric? ch)))
+		   (next-char)
+		   (set! num-str-end (+ 1 num-str-end)))
+		 (set! params
+		       (append params
+			       (list (string->number
+				      (substring format-string
+						 num-str-beg
+						 num-str-end))))))
+	       (set! param-value-found #t)
+	       (tilde-dispatch))
+	      ((#\V)			; Variable parameter from next argum.
+	       (if modifier (format:error "misplaced modifier"))
+	       (set! params (append params (list (next-arg))))
+	       (set! param-value-found #t)
+	       (tilde-dispatch))
+	      ((#\#)			; Parameter is number of remaining args
+	       (if modifier (format:error "misplaced modifier"))
+	       (set! params (append params (list (length (rest-args)))))
+	       (set! param-value-found #t)
+	       (tilde-dispatch))
+	      ((#\,)			; Parameter separators
+	       (if modifier (format:error "misplaced modifier"))
+	       (if (not param-value-found)
+		   (set! params (append params '(#f)))) ; append empty paramtr
+	       (set! param-value-found #f)
+	       (tilde-dispatch))
+	      ((#\Q)			; Inquiry messages
+	       (if (eq? modifier 'colon)
+		   (format:out-str format:version)
+		   (let ((nl (string #\newline)))
+		     (format:out-str
+		      (string-append
+		       "SLIB Common LISP format version " format:version nl
+		       "  (C) copyright 1992-1994 by Dirk Lutzebaeck" nl
+		       "  please send bug reports to `lutzeb@cs.tu-berlin.de'"
+		       nl))))
+	       (anychar-dispatch))
+	      (else			; Unknown tilde directive
+	       (format:error "unknown control character `~c'"
+		      (string-ref format-string (- format:pos 1))))))
+	   (else (anychar-dispatch)))))) ; in case of conditional
+
+    (set! format:pos 0)
+    (set! format:arg-pos 0)
+    (anychar-dispatch)			; start the formatting
+    (set! format:pos recursive-pos-save)
+    arg-pos))				; return the position in the arg. list
+
+;; format:obj->str returns a R4RS representation as a string of an arbitrary
+;; scheme object.
+;; First parameter is the object, second parameter is a boolean if the
+;; representation should be slashified as `write' does.
+;; It uses format:char->str which converts a character into
+;; a slashified string as `write' does and which is implementation dependent.
+;; It uses format:iobj->str to print out internal objects as
+;; quoted strings so that the output can always be processed by (read)
+
+(define (format:obj->str obj slashify)
+  (cond
+   ((string? obj)
+    (if slashify
+	(let ((obj-len (string-length obj)))
+	  (string-append
+	   "\""
+	   (let loop ((i 0) (j 0))	; taken from Marc Feeley's pp.scm
+	     (if (= j obj-len)
+		 (string-append (substring obj i j) "\"")
+		 (let ((c (string-ref obj j)))
+		   (if (or (char=? c #\\)
+			   (char=? c #\"))
+		       (string-append (substring obj i j) "\\"
+				      (loop j (+ j 1)))
+		       (loop i (+ j 1))))))))
+	obj))
+   
+   ((boolean? obj) (if obj "#t" "#f"))
+   
+   ((number? obj) (number->string obj))
+
+   ((symbol? obj) 
+    (if format:symbol-case-conv
+	(format:symbol-case-conv (symbol->string obj))
+	(symbol->string obj)))
+   
+   ((char? obj)
+    (if slashify
+	(format:char->str obj)
+	(string obj)))
+   
+   ((null? obj) "()")
+
+   ((input-port? obj)
+    (format:iobj->str obj))
+   
+   ((output-port? obj)
+    (format:iobj->str obj))
+     
+   ((list? obj)
+    (string-append "("
+		   (let loop ((obj-list obj))
+		     (if (null? (cdr obj-list))
+			 (format:obj->str (car obj-list) #t)
+			 (string-append
+			  (format:obj->str (car obj-list) #t)
+			  " "
+			  (loop (cdr obj-list)))))
+		   ")"))
+
+   ((pair? obj)
+    (string-append "("
+		   (format:obj->str (car obj) #t)
+		   " . "
+		   (format:obj->str (cdr obj) #t)
+		   ")"))
+   
+   ((vector? obj)
+    (string-append "#" (format:obj->str (vector->list obj) #t)))
+
+   (else				; only objects with an #<...> 
+    (format:iobj->str obj))))		; representation should fall in here
+
+;; format:iobj->str reveals the implementation dependent representation of 
+;; #<...> objects with the use of display and call-with-output-string.
+;; If format:read-proof is set to #t the resulting string is additionally 
+;; set into string quotes.
+
+(define format:read-proof #f)
+
+(define (format:iobj->str iobj)
+  (if (or format:read-proof
+	  format:iobj-case-conv)
+      (string-append 
+       (if format:read-proof "\"" "")
+       (if format:iobj-case-conv
+	   (format:iobj-case-conv
+	    (call-with-output-string (lambda (p) (display iobj p))))
+	   (call-with-output-string (lambda (p) (display iobj p))))
+       (if format:read-proof "\"" ""))
+      (call-with-output-string (lambda (p) (display iobj p)))))
+
+
+;; format:char->str converts a character into a slashified string as
+;; done by `write'. The procedure is dependent on the integer
+;; representation of characters and assumes a character number according to
+;; the ASCII character set.
+
+(define (format:char->str ch)
+  (let ((int-rep (char->integer ch)))
+    (if (< int-rep 0)			; if chars are [-128...+127]
+	(set! int-rep (+ int-rep 256)))
+    (string-append
+     "#\\"
+     (cond
+      ((char=? ch #\newline) "newline")
+      ((and (>= int-rep 0) (<= int-rep 32))
+       (vector-ref format:ascii-non-printable-charnames int-rep))
+      ((= int-rep 127) "del")
+      ((>= int-rep 128)		; octal representation
+       (if format:radix-pref
+	   (let ((s (number->string int-rep 8)))
+	     (substring s 2 (string-length s)))
+	   (number->string int-rep 8)))
+      (else (string ch))))))
+
+(define format:space-ch (char->integer #\space))
+(define format:zero-ch (char->integer #\0))
+
+(define (format:par pars length index default name)
+  (if (> length index)
+      (let ((par (list-ref pars index)))
+	(if par
+	    (if name
+		(if (< par 0)
+		    (format:error 
+		     "~s parameter must be a positive integer" name)
+		    par)
+		par)
+	    default))
+      default))
+
+(define (format:out-obj-padded pad-left obj slashify pars)
+  (if (null? pars)
+      (format:out-str (format:obj->str obj slashify))
+      (let ((l (length pars)))
+	(let ((mincol (format:par pars l 0 0 "mincol"))
+	      (colinc (format:par pars l 1 1 "colinc"))
+	      (minpad (format:par pars l 2 0 "minpad"))
+	      (padchar (integer->char
+			(format:par pars l 3 format:space-ch #f)))
+	      (objstr (format:obj->str obj slashify)))
+	  (if (not pad-left)
+	      (format:out-str objstr))
+	  (do ((objstr-len (string-length objstr))
+	       (i minpad (+ i colinc)))
+	      ((>= (+ objstr-len i) mincol)
+	       (format:out-fill i padchar)))
+	  (if pad-left
+	      (format:out-str objstr))))))
+
+(define (format:out-num-padded modifier number pars radix)
+  (if (not (integer? number)) (format:error "argument not an integer"))
+  (let ((numstr (number->string number radix)))
+    (if (and format:radix-pref (not (= radix 10)))
+	(set! numstr (substring numstr 2 (string-length numstr))))
+    (if (and (null? pars) (not modifier))
+	(format:out-str numstr)
+	(let ((l (length pars))
+	      (numstr-len (string-length numstr)))
+	  (let ((mincol (format:par pars l 0 #f "mincol"))
+		(padchar (integer->char
+			  (format:par pars l 1 format:space-ch #f)))
+		(commachar (integer->char
+			    (format:par pars l 2 (char->integer #\,) #f)))
+		(commawidth (format:par pars l 3 3 "commawidth")))
+	    (if mincol
+		(let ((numlen numstr-len)) ; calc. the output len of number
+		  (if (and (memq modifier '(at colon-at)) (> number 0))
+		      (set! numlen (+ numlen 1)))
+		  (if (memq modifier '(colon colon-at))
+		      (set! numlen (+ (quotient (- numstr-len 
+						   (if (< number 0) 2 1))
+						commawidth)
+				      numlen)))
+		  (if (> mincol numlen)
+		      (format:out-fill (- mincol numlen) padchar))))
+	    (if (and (memq modifier '(at colon-at))
+		     (> number 0))
+		(format:out-char #\+))
+	    (if (memq modifier '(colon colon-at)) ; insert comma character
+		(let ((start (remainder numstr-len commawidth))
+		      (ns (if (< number 0) 1 0)))
+		  (format:out-substr numstr 0 start)
+		  (do ((i start (+ i commawidth)))
+		      ((>= i numstr-len))
+		    (if (> i ns)
+			(format:out-char commachar))
+		    (format:out-substr numstr i (+ i commawidth))))
+		(format:out-str numstr)))))))
+
+(define (format:tabulate modifier pars)
+  (let ((l (length pars)))
+    (let ((colnum (format:par pars l 0 1 "colnum"))
+	  (colinc (format:par pars l 1 1 "colinc"))
+	  (padch (integer->char (format:par pars l 2 format:space-ch #f))))
+      (case modifier
+	((colon colon-at)
+	 (format:error "unsupported modifier for ~~t"))
+	((at)				; relative tabulation
+	 (format:out-fill
+	  (if (= colinc 0)
+	      colnum			; colnum = colrel
+	      (do ((c 0 (+ c colinc))
+		   (col (+ format:output-col colnum)))
+		  ((>= c col)
+		   (- c format:output-col))))
+	  padch))
+	(else				; absolute tabulation
+	 (format:out-fill
+	  (cond
+	   ((< format:output-col colnum)
+	    (- colnum format:output-col))
+	   ((= colinc 0)
+	    0)
+	   (else
+	    (do ((c colnum (+ c colinc)))
+		((>= c format:output-col)
+		 (- c format:output-col)))))
+	  padch))))))
+
+
+;; roman numerals (from dorai@cs.rice.edu).
+
+(define format:roman-alist
+  '((1000 #\M) (500 #\D) (100 #\C) (50 #\L)
+    (10 #\X) (5 #\V) (1 #\I)))
+
+(define format:roman-boundary-values
+  '(100 100 10 10 1 1 #f))
+
+(define format:num->old-roman
+  (lambda (n)
+    (if (and (integer? n) (>= n 1))
+	(let loop ((n n)
+		   (romans format:roman-alist)
+		   (s '()))
+	  (if (null? romans) (list->string (reverse s))
+	      (let ((roman-val (caar romans))
+		    (roman-dgt (cadar romans)))
+		(do ((q (quotient n roman-val) (- q 1))
+		     (s s (cons roman-dgt s)))
+		    ((= q 0)
+		     (loop (remainder n roman-val)
+		       (cdr romans) s))))))
+	(format:error "only positive integers can be romanized"))))
+
+(define format:num->roman
+  (lambda (n)
+    (if (and (integer? n) (> n 0))
+	(let loop ((n n)
+		   (romans format:roman-alist)
+		   (boundaries format:roman-boundary-values)
+		   (s '()))
+	  (if (null? romans)
+	      (list->string (reverse s))
+	      (let ((roman-val (caar romans))
+		    (roman-dgt (cadar romans))
+		    (bdry (car boundaries)))
+		(let loop2 ((q (quotient n roman-val))
+			    (r (remainder n roman-val))
+			    (s s))
+		  (if (= q 0)
+		      (if (and bdry (>= r (- roman-val bdry)))
+			  (loop (remainder r bdry) (cdr romans)
+			    (cdr boundaries)
+			    (cons roman-dgt
+			      (append
+				(cdr (assv bdry romans))
+				s)))
+			  (loop r (cdr romans) (cdr boundaries) s))
+		      (loop2 (- q 1) r (cons roman-dgt s)))))))
+	(format:error "only positive integers can be romanized"))))
+
+;; cardinals & ordinals (from dorai@cs.rice.edu)
+
+(define format:cardinal-ones-list
+  '(#f "one" "two" "three" "four" "five"
+     "six" "seven" "eight" "nine" "ten" "eleven" "twelve" "thirteen"
+     "fourteen" "fifteen" "sixteen" "seventeen" "eighteen"
+     "nineteen"))
+
+(define format:cardinal-tens-list
+  '(#f #f "twenty" "thirty" "forty" "fifty" "sixty" "seventy" "eighty"
+     "ninety"))
+
+(define format:num->cardinal999
+  (lambda (n)
+    ;this procedure is inspired by the Bruno Haible's CLisp
+    ;function format-small-cardinal, which converts numbers
+    ;in the range 1 to 999, and is used for converting each
+    ;thousand-block in a larger number
+    (let* ((hundreds (quotient n 100))
+	   (tens+ones (remainder n 100))
+	   (tens (quotient tens+ones 10))
+	   (ones (remainder tens+ones 10)))
+      (append
+	(if (> hundreds 0)
+	    (append
+	      (string->list
+		(list-ref format:cardinal-ones-list hundreds))
+	      (string->list" hundred")
+	      (if (> tens+ones 0) '(#\space) '()))
+	    '())
+	(if (< tens+ones 20)
+	    (if (> tens+ones 0)
+		(string->list
+		  (list-ref format:cardinal-ones-list tens+ones))
+		'())
+	    (append
+	      (string->list
+		(list-ref format:cardinal-tens-list tens))
+	      (if (> ones 0)
+		  (cons #\-
+		    (string->list
+		      (list-ref format:cardinal-ones-list ones))))))))))
+
+(define format:cardinal-thousand-block-list
+  '("" " thousand" " million" " billion" " trillion" " quadrillion"
+     " quintillion" " sextillion" " septillion" " octillion" " nonillion"
+     " decillion" " undecillion" " duodecillion" " tredecillion"
+     " quattuordecillion" " quindecillion" " sexdecillion" " septendecillion"
+     " octodecillion" " novemdecillion" " vigintillion"))
+
+(define format:num->cardinal
+  (lambda (n)
+    (cond ((not (integer? n))
+	   (format:error
+	     "only integers can be converted to English cardinals"))
+	  ((= n 0) "zero")
+	  ((< n 0) (string-append "minus " (format:num->cardinal (- n))))
+	  (else
+	    (let ((power3-word-limit
+		    (length format:cardinal-thousand-block-list)))
+	      (let loop ((n n)
+			 (power3 0)
+			 (s '()))
+		(if (= n 0)
+		    (list->string s)
+		    (let ((n-before-block (quotient n 1000))
+			  (n-after-block (remainder n 1000)))
+		      (loop n-before-block
+			(+ power3 1)
+			(if (> n-after-block 0)
+			    (append
+			      (if (> n-before-block 0)
+				  (string->list ", ") '())
+			      (format:num->cardinal999 n-after-block)
+			      (if (< power3 power3-word-limit)
+				  (string->list
+				    (list-ref
+				     format:cardinal-thousand-block-list
+				     power3))
+				  (append
+				    (string->list " times ten to the ")
+				    (string->list
+				      (format:num->ordinal
+					(* power3 3)))
+				    (string->list " power")))
+			      s)
+			    s))))))))))
+
+(define format:ordinal-ones-list
+  '(#f "first" "second" "third" "fourth" "fifth"
+     "sixth" "seventh" "eighth" "ninth" "tenth" "eleventh" "twelfth"
+     "thirteenth" "fourteenth" "fifteenth" "sixteenth" "seventeenth"
+     "eighteenth" "nineteenth"))
+
+(define format:ordinal-tens-list
+  '(#f #f "twentieth" "thirtieth" "fortieth" "fiftieth" "sixtieth"
+     "seventieth" "eightieth" "ninetieth"))
+
+(define format:num->ordinal
+  (lambda (n)
+    (cond ((not (integer? n))
+	   (format:error
+	     "only integers can be converted to English ordinals"))
+	  ((= n 0) "zeroth")
+	  ((< n 0) (string-append "minus " (format:num->ordinal (- n))))
+	  (else
+	    (let ((hundreds (quotient n 100))
+		  (tens+ones (remainder n 100)))
+	      (string-append
+		(if (> hundreds 0)
+		    (string-append
+		      (format:num->cardinal (* hundreds 100))
+		      (if (= tens+ones 0) "th" " "))
+		    "")
+		(if (= tens+ones 0) ""
+		    (if (< tens+ones 20)
+			(list-ref format:ordinal-ones-list tens+ones)
+			(let ((tens (quotient tens+ones 10))
+			      (ones (remainder tens+ones 10)))
+			  (if (= ones 0)
+			      (list-ref format:ordinal-tens-list tens)
+			      (string-append
+				(list-ref format:cardinal-tens-list tens)
+				"-"
+				(list-ref format:ordinal-ones-list ones))))
+			))))))))
+
+;; format fixed flonums (~F)
+
+(define (format:out-fixed modifier number pars)
+  (if (not (or (number? number) (string? number)))
+      (format:error "argument is not a number or a number string"))
+
+  (let ((l (length pars)))
+    (let ((width (format:par pars l 0 #f "width"))
+	  (digits (format:par pars l 1 #f "digits"))
+	  (scale (format:par pars l 2 0 #f))
+	  (overch (format:par pars l 3 #f #f))
+	  (padch (format:par pars l 4 format:space-ch #f)))
+
+    (if digits
+
+	(begin				; fixed precision
+	  (format:parse-float 
+	   (if (string? number) number (number->string number)) #t scale)
+	  (if (<= (- format:fn-len format:fn-dot) digits)
+	      (format:fn-zfill #f (- digits (- format:fn-len format:fn-dot)))
+	      (format:fn-round digits))
+	  (if width
+	      (let ((numlen (+ format:fn-len 1)))
+		(if (or (not format:fn-pos?) (eq? modifier 'at))
+		    (set! numlen (+ numlen 1)))
+		(if (and (= format:fn-dot 0) (> width (+ digits 1)))
+		    (set! numlen (+ numlen 1)))
+		(if (< numlen width)
+		    (format:out-fill (- width numlen) (integer->char padch)))
+		(if (and overch (> numlen width))
+		    (format:out-fill width (integer->char overch))
+		    (format:fn-out modifier (> width (+ digits 1)))))
+	      (format:fn-out modifier #t)))
+
+	(begin				; free precision
+	  (format:parse-float
+	   (if (string? number) number (number->string number)) #t scale)
+	  (format:fn-strip)
+	  (if width
+	      (let ((numlen (+ format:fn-len 1)))
+		(if (or (not format:fn-pos?) (eq? modifier 'at))
+		    (set! numlen (+ numlen 1)))
+		(if (= format:fn-dot 0)
+		    (set! numlen (+ numlen 1)))
+		(if (< numlen width)
+		    (format:out-fill (- width numlen) (integer->char padch)))
+		(if (> numlen width)	; adjust precision if possible
+		    (let ((dot-index (- numlen
+					(- format:fn-len format:fn-dot))))
+		      (if (> dot-index width)
+			  (if overch	; numstr too big for required width
+			      (format:out-fill width (integer->char overch))
+			      (format:fn-out modifier #t))
+			  (begin
+			    (format:fn-round (- width dot-index))
+			    (format:fn-out modifier #t))))
+		    (format:fn-out modifier #t)))
+	      (format:fn-out modifier #t)))))))
+
+;; format exponential flonums (~E)
+
+(define (format:out-expon modifier number pars)
+  (if (not (or (number? number) (string? number)))
+      (format:error "argument is not a number"))
+
+  (let ((l (length pars)))
+    (let ((width (format:par pars l 0 #f "width"))
+	  (digits (format:par pars l 1 #f "digits"))
+	  (edigits (format:par pars l 2 #f "exponent digits"))
+	  (scale (format:par pars l 3 1 #f))
+	  (overch (format:par pars l 4 #f #f))
+	  (padch (format:par pars l 5 format:space-ch #f))
+	  (expch (format:par pars l 6 #f #f)))
+	 
+    (if digits				; fixed precision
+
+	(let ((digits (if (> scale 0)
+			  (if (< scale (+ digits 2))
+			      (+ (- digits scale) 1)
+			      0)
+			  digits)))
+	  (format:parse-float 
+	   (if (string? number) number (number->string number)) #f scale)
+	  (if (<= (- format:fn-len format:fn-dot) digits)
+	      (format:fn-zfill #f (- digits (- format:fn-len format:fn-dot)))
+	      (format:fn-round digits))
+	  (if width
+	      (if (and edigits overch (> format:en-len edigits))
+		  (format:out-fill width (integer->char overch))
+		  (let ((numlen (+ format:fn-len 3))) ; .E+
+		    (if (or (not format:fn-pos?) (eq? modifier 'at))
+			(set! numlen (+ numlen 1)))
+		    (if (and (= format:fn-dot 0) (> width (+ digits 1)))
+			(set! numlen (+ numlen 1)))	
+		    (set! numlen
+			  (+ numlen 
+			     (if (and edigits (>= edigits format:en-len))
+				 edigits 
+				 format:en-len)))
+		    (if (< numlen width)
+			(format:out-fill (- width numlen)
+					 (integer->char padch)))
+		    (if (and overch (> numlen width))
+			(format:out-fill width (integer->char overch))
+			(begin
+			  (format:fn-out modifier (> width (- numlen 1)))
+			  (format:en-out edigits expch)))))
+	      (begin
+		(format:fn-out modifier #t)
+		(format:en-out edigits expch))))
+
+	(begin				; free precision
+	  (format:parse-float
+	   (if (string? number) number (number->string number)) #f scale)
+	  (format:fn-strip)
+	  (if width
+	      (if (and edigits overch (> format:en-len edigits))
+		  (format:out-fill width (integer->char overch))
+		  (let ((numlen (+ format:fn-len 3))) ; .E+
+		    (if (or (not format:fn-pos?) (eq? modifier 'at))
+			(set! numlen (+ numlen 1)))
+		    (if (= format:fn-dot 0)
+			(set! numlen (+ numlen 1)))
+		    (set! numlen
+			  (+ numlen
+			     (if (and edigits (>= edigits format:en-len))
+				 edigits 
+				 format:en-len)))
+		    (if (< numlen width)
+			(format:out-fill (- width numlen)
+					 (integer->char padch)))
+		    (if (> numlen width) ; adjust precision if possible
+			(let ((f (- format:fn-len format:fn-dot))) ; fract len
+			  (if (> (- numlen f) width)
+			      (if overch ; numstr too big for required width
+				  (format:out-fill width 
+						   (integer->char overch))
+				  (begin
+				    (format:fn-out modifier #t)
+				    (format:en-out edigits expch)))
+			      (begin
+				(format:fn-round (+ (- f numlen) width))
+				(format:fn-out modifier #t)
+				(format:en-out edigits expch))))
+			(begin
+			  (format:fn-out modifier #t)
+			  (format:en-out edigits expch)))))
+	      (begin
+		(format:fn-out modifier #t)
+		(format:en-out edigits expch))))))))
+	
+;; format general flonums (~G)
+
+(define (format:out-general modifier number pars)
+  (if (not (or (number? number) (string? number)))
+      (format:error "argument is not a number or a number string"))
+
+  (let ((l (length pars)))
+    (let ((width (if (> l 0) (list-ref pars 0) #f))
+	  (digits (if (> l 1) (list-ref pars 1) #f))
+	  (edigits (if (> l 2) (list-ref pars 2) #f))
+	  (overch (if (> l 4) (list-ref pars 4) #f))
+	  (padch (if (> l 5) (list-ref pars 5) #f)))
+    (format:parse-float
+     (if (string? number) number (number->string number)) #t 0)
+    (format:fn-strip)
+    (let* ((ee (if edigits (+ edigits 2) 4)) ; for the following algorithm
+	   (ww (if width (- width ee) #f))   ; see Steele's CL book p.395
+	   (n (if (= format:fn-dot 0)	; number less than (abs 1.0) ?
+		  (- (format:fn-zlead))
+		  format:fn-dot))
+	   (d (if digits
+		  digits
+		  (max format:fn-len (min n 7)))) ; q = format:fn-len
+	   (dd (- d n)))
+      (if (<= 0 dd d)
+	  (begin
+	    (format:out-fixed modifier number (list ww dd #f overch padch))
+	    (format:out-fill ee #\space)) ;~@T not implemented yet
+	  (format:out-expon modifier number pars))))))
+
+;; format dollar flonums (~$)
+
+(define (format:out-dollar modifier number pars)
+  (if (not (or (number? number) (string? number)))
+      (format:error "argument is not a number or a number string"))
+
+  (let ((l (length pars)))
+    (let ((digits (format:par pars l 0 2 "digits"))
+	  (mindig (format:par pars l 1 1 "mindig"))
+	  (width (format:par pars l 2 0 "width"))
+	  (padch (format:par pars l 3 format:space-ch #f)))
+
+    (format:parse-float
+     (if (string? number) number (number->string number)) #t 0)
+    (if (<= (- format:fn-len format:fn-dot) digits)
+	(format:fn-zfill #f (- digits (- format:fn-len format:fn-dot)))
+	(format:fn-round digits))
+    (let ((numlen (+ format:fn-len 1)))
+      (if (or (not format:fn-pos?) (memq modifier '(at colon-at)))
+	  (set! numlen (+ numlen 1)))
+      (if (and mindig (> mindig format:fn-dot))
+	  (set! numlen (+ numlen (- mindig format:fn-dot))))
+      (if (and (= format:fn-dot 0) (not mindig))
+	  (set! numlen (+ numlen 1)))
+      (if (< numlen width)
+	  (case modifier
+	    ((colon)
+	     (if (not format:fn-pos?)
+		 (format:out-char #\-))
+	     (format:out-fill (- width numlen) (integer->char padch)))
+	    ((at)
+	     (format:out-fill (- width numlen) (integer->char padch))
+	     (format:out-char (if format:fn-pos? #\+ #\-)))
+	    ((colon-at)
+	     (format:out-char (if format:fn-pos? #\+ #\-))
+	     (format:out-fill (- width numlen) (integer->char padch)))
+	    (else
+	     (format:out-fill (- width numlen) (integer->char padch))
+	     (if (not format:fn-pos?)
+		 (format:out-char #\-))))
+	  (if format:fn-pos?
+	      (if (memq modifier '(at colon-at)) (format:out-char #\+))
+	      (format:out-char #\-))))
+    (if (and mindig (> mindig format:fn-dot))
+	(format:out-fill (- mindig format:fn-dot) #\0))
+    (if (and (= format:fn-dot 0) (not mindig))
+	(format:out-char #\0))
+    (format:out-substr format:fn-str 0 format:fn-dot)
+    (format:out-char #\.)
+    (format:out-substr format:fn-str format:fn-dot format:fn-len))))
+
+; the flonum buffers
+
+(define format:fn-max 200)		; max. number of number digits
+(define format:fn-str (make-string format:fn-max)) ; number buffer
+(define format:fn-len 0)		; digit length of number
+(define format:fn-dot #f)		; dot position of number
+(define format:fn-pos? #t)		; number positive?
+(define format:en-max 10)		; max. number of exponent digits
+(define format:en-str (make-string format:en-max)) ; exponent buffer
+(define format:en-len 0)		; digit length of exponent
+(define format:en-pos? #t)		; exponent positive?
+
+(define (format:parse-float num-str fixed? scale)
+  (set! format:fn-pos? #t)
+  (set! format:fn-len 0)
+  (set! format:fn-dot #f)
+  (set! format:en-pos? #t)
+  (set! format:en-len 0)
+  (do ((i 0 (+ i 1))
+       (left-zeros 0)
+       (mantissa? #t)
+       (all-zeros? #t)
+       (num-len (string-length num-str))
+       (c #f))			; current exam. character in num-str
+      ((= i num-len)
+       (if (not format:fn-dot)
+	   (set! format:fn-dot format:fn-len))
+
+       (if all-zeros?
+	   (begin
+	     (set! left-zeros 0)
+	     (set! format:fn-dot 0)
+	     (set! format:fn-len 1)))
+
+       ;; now format the parsed values according to format's need
+
+       (if fixed?
+
+	   (begin			; fixed format m.nnn or .nnn
+	     (if (and (> left-zeros 0) (> format:fn-dot 0))
+		 (if (> format:fn-dot left-zeros) 
+		     (begin		; norm 0{0}nn.mm to nn.mm
+		       (format:fn-shiftleft left-zeros)
+		       (set! left-zeros 0)
+		       (set! format:fn-dot (- format:fn-dot left-zeros)))
+		     (begin		; normalize 0{0}.nnn to .nnn
+		       (format:fn-shiftleft format:fn-dot)
+		       (set! left-zeros (- left-zeros format:fn-dot))
+		       (set! format:fn-dot 0))))
+	     (if (or (not (= scale 0)) (> format:en-len 0))
+		 (let ((shift (+ scale (format:en-int))))
+		   (cond
+		    (all-zeros? #t)
+		    ((> (+ format:fn-dot shift) format:fn-len)
+		     (format:fn-zfill
+		      #f (- shift (- format:fn-len format:fn-dot)))
+		     (set! format:fn-dot format:fn-len))
+		    ((< (+ format:fn-dot shift) 0)
+		     (format:fn-zfill #t (- (- shift) format:fn-dot))
+		     (set! format:fn-dot 0))
+		    (else
+		     (if (> left-zeros 0)
+			 (if (<= left-zeros shift) ; shift always > 0 here
+			     (format:fn-shiftleft shift) ; shift out 0s
+			     (begin
+			       (format:fn-shiftleft left-zeros)
+			       (set! format:fn-dot (- shift left-zeros))))
+			 (set! format:fn-dot (+ format:fn-dot shift))))))))
+
+	   (let ((negexp		; expon format m.nnnEee
+		  (if (> left-zeros 0)
+		      (- left-zeros format:fn-dot -1)
+		      (if (= format:fn-dot 0) 1 0))))
+	     (if (> left-zeros 0)
+		 (begin			; normalize 0{0}.nnn to n.nn
+		   (format:fn-shiftleft left-zeros)
+		   (set! format:fn-dot 1))
+		 (if (= format:fn-dot 0)
+		     (set! format:fn-dot 1)))
+	     (format:en-set (- (+ (- format:fn-dot scale) (format:en-int))
+			       negexp))
+	     (cond 
+	      (all-zeros?
+	       (format:en-set 0)
+	       (set! format:fn-dot 1))
+	      ((< scale 0)		; leading zero
+	       (format:fn-zfill #t (- scale))
+	       (set! format:fn-dot 0))
+	      ((> scale format:fn-dot)
+	       (format:fn-zfill #f (- scale format:fn-dot))
+	       (set! format:fn-dot scale))
+	      (else
+	       (set! format:fn-dot scale)))))
+       #t)
+
+    ;; do body      
+    (set! c (string-ref num-str i))	; parse the output of number->string
+    (cond				; which can be any valid number
+     ((char-numeric? c)			; representation of R4RS except 
+      (if mantissa?			; complex numbers
+	  (begin
+	    (if (char=? c #\0)
+		(if all-zeros?
+		    (set! left-zeros (+ left-zeros 1)))
+		(begin
+		  (set! all-zeros? #f)))
+	    (string-set! format:fn-str format:fn-len c)
+	    (set! format:fn-len (+ format:fn-len 1)))
+	  (begin
+	    (string-set! format:en-str format:en-len c)
+	    (set! format:en-len (+ format:en-len 1)))))
+     ((or (char=? c #\-) (char=? c #\+))
+      (if mantissa?
+	  (set! format:fn-pos? (char=? c #\+))
+	  (set! format:en-pos? (char=? c #\+))))
+     ((char=? c #\.)
+      (set! format:fn-dot format:fn-len))
+     ((char=? c #\e)
+      (set! mantissa? #f))
+     ((char=? c #\E)
+      (set! mantissa? #f))
+     ((char-whitespace? c) #t)
+     ((char=? c #\d) #t)		; decimal radix prefix
+     ((char=? c #\#) #t)
+     (else
+      (format:error "illegal character `~c' in number->string" c)))))
+
+(define (format:en-int)			; convert exponent string to integer
+  (if (= format:en-len 0)
+      0
+      (do ((i 0 (+ i 1))
+	   (n 0))
+	  ((= i format:en-len) 
+	   (if format:en-pos?
+	       n
+	       (- n)))
+	(set! n (+ (* n 10) (- (char->integer (string-ref format:en-str i))
+			       format:zero-ch))))))
+
+(define (format:en-set en)		; set exponent string number
+  (set! format:en-len 0)
+  (set! format:en-pos? (>= en 0))
+  (let ((en-str (number->string en)))
+    (do ((i 0 (+ i 1))
+	 (en-len (string-length en-str))
+	 (c #f))
+	((= i en-len))
+      (set! c (string-ref en-str i))
+      (if (char-numeric? c)
+	  (begin
+	    (string-set! format:en-str format:en-len c)
+	    (set! format:en-len (+ format:en-len 1)))))))
+
+(define (format:fn-zfill left? n)	; fill current number string with 0s
+  (if (> (+ n format:fn-len) format:fn-max) ; from the left or right
+      (format:error "number is too long to format (enlarge format:fn-max)"))
+  (set! format:fn-len (+ format:fn-len n))
+  (if left?
+      (do ((i format:fn-len (- i 1)))	; fill n 0s to left
+	  ((< i 0))
+	(string-set! format:fn-str i
+		     (if (< i n)
+			 #\0
+			 (string-ref format:fn-str (- i n)))))
+      (do ((i (- format:fn-len n) (+ i 1))) ; fill n 0s to the right
+	  ((= i format:fn-len))
+	(string-set! format:fn-str i #\0))))
+
+(define (format:fn-shiftleft n)		; shift left current number n positions
+  (if (> n format:fn-len)
+      (format:error "internal error in format:fn-shiftleft (~d,~d)"
+		    n format:fn-len))
+  (do ((i n (+ i 1)))
+      ((= i format:fn-len)
+       (set! format:fn-len (- format:fn-len n)))
+    (string-set! format:fn-str (- i n) (string-ref format:fn-str i))))
+
+(define (format:fn-round digits)	; round format:fn-str
+  (set! digits (+ digits format:fn-dot))
+  (do ((i digits (- i 1))		; "099",2 -> "10"
+       (c 5))				; "023",2 -> "02"
+      ((or (= c 0) (< i 0))		; "999",2 -> "100"
+       (if (= c 1)			; "005",2 -> "01"
+	   (begin			; carry overflow
+	     (set! format:fn-len digits)
+	     (format:fn-zfill #t 1)	; add a 1 before fn-str
+	     (string-set! format:fn-str 0 #\1)
+	     (set! format:fn-dot (+ format:fn-dot 1)))
+	   (set! format:fn-len digits)))
+    (set! c (+ (- (char->integer (string-ref format:fn-str i))
+		  format:zero-ch) c))
+    (string-set! format:fn-str i (integer->char
+				  (if (< c 10) 
+				      (+ c format:zero-ch)
+				      (+ (- c 10) format:zero-ch))))
+    (set! c (if (< c 10) 0 1))))
+
+(define (format:fn-out modifier add-leading-zero?)
+  (if format:fn-pos?
+      (if (eq? modifier 'at) 
+	  (format:out-char #\+))
+      (format:out-char #\-))
+  (if (= format:fn-dot 0)
+      (if add-leading-zero?
+	  (format:out-char #\0))
+      (format:out-substr format:fn-str 0 format:fn-dot))
+  (format:out-char #\.)
+  (format:out-substr format:fn-str format:fn-dot format:fn-len))
+
+(define (format:en-out edigits expch)
+  (format:out-char (if expch (integer->char expch) format:expch))
+  (format:out-char (if format:en-pos? #\+ #\-))
+  (if edigits 
+      (if (< format:en-len edigits)
+	  (format:out-fill (- edigits format:en-len) #\0)))
+  (format:out-substr format:en-str 0 format:en-len))
+
+(define (format:fn-strip)		; strip trailing zeros but one
+  (string-set! format:fn-str format:fn-len #\0)
+  (do ((i format:fn-len (- i 1)))
+      ((or (not (char=? (string-ref format:fn-str i) #\0))
+	   (<= i format:fn-dot))
+       (set! format:fn-len (+ i 1)))))
+
+(define (format:fn-zlead)		; count leading zeros
+  (do ((i 0 (+ i 1)))
+      ((or (= i format:fn-len)
+	   (not (char=? (string-ref format:fn-str i) #\0)))
+       (if (= i format:fn-len)		; found a real zero
+	   0
+	   i))))
+
+
+;;; some global functions not found in SLIB
+
+;; string-index finds the index of the first occurence of the character `c'
+;; in the string `s'; it returns #f if there is no such character in `s'.
+
+(define (string-index s c)
+  (let ((slen-1 (- (string-length s) 1)))
+    (let loop ((i 0))
+      (cond
+       ((char=? c (string-ref s i)) i)
+       ((= i slen-1) #f)
+       (else (loop (+ i 1)))))))
+
+(define (string-capitalize-first str)	; "hello" -> "Hello"
+  (let ((cap-str (string-copy str))	; "hELLO" -> "Hello"
+	(non-first-alpha #f)		; "*hello" -> "*Hello"
+	(str-len (string-length str)))	; "hello you" -> "Hello you"
+    (do ((i 0 (+ i 1)))
+	((= i str-len) cap-str)
+      (let ((c (string-ref str i)))
+	(if (char-alphabetic? c)
+	    (if non-first-alpha
+		(string-set! cap-str i (char-downcase c))
+		(begin
+		  (set! non-first-alpha #t)
+		  (string-set! cap-str i (char-upcase c)))))))))
+
+(define (list-head l k)
+  (if (= k 0)
+      '()
+      (cons (car l) (list-head (cdr l) (- k 1)))))
+
+
+;; Aborts the program when a formatting error occures. This is a null
+;; argument closure to jump to the interpreters toplevel continuation.
+
+(define format:abort (lambda () (slib:error "error in format")))
+
+(define format format:format)
+
+;; If this is not possible then a continuation is used to recover
+;; properly from a format error. In this case format returns #f.
+
+;(define format:abort
+;  (lambda () (format:error-continuation #f)))
+
+;(define format
+;  (lambda args				; wraps format:format with an error
+;    (call-with-current-continuation	; continuation
+;     (lambda (cont)
+;       (set! format:error-continuation cont)
+;       (apply format:format args)))))
+
+;eof