[lisp] / optparse.lisp

;;; -*-lisp-*-
;;;
;;; $Id$
;;;
;;; Option parser, standard issue
;;;
;;; (c) 2005 Straylight/Edgeware
;;;

;;;----- Licensing notice ---------------------------------------------------
;;;
;;; This program is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 2 of the License, or
;;; (at your option) any later version.
;;; 
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;; 
;;; You should have received a copy of the GNU General Public License
;;; along with this program; if not, write to the Free Software Foundation,
;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

;;;--------------------------------------------------------------------------
;;; Packages.

(defpackage #:optparse
  (:use #:common-lisp #:mdw.base #:mdw.sys-base #:mdw.str)
  (:export #:exit #:*program-name* #:*command-line-strings*
	   #:moan #:die
	   #:option #:optionp #:make-option
	     #:opt-short-name #:opt-long-name #:opt-tag #:opt-negated-tag
	     #:opt-arg-name #:opt-arg-optional-p #:opt-documentation
	   #:option-parser #:make-option-parser #:option-parser-p
	     #:op-options #:op-non-option #:op-long-only-p #:op-numeric-p
	     #:op-negated-numeric-p #:op-negated-p
	   #:option-parse-error
	   #:option-parse-remainder #:option-parse-next #:option-parse-try
	     #:with-unix-error-reporting 
	   #:defopthandler #:invoke-option-handler
	     #:set #:clear #:inc #:dec #:read #:int #:string
	     #:keyword #:list
	   #:parse-option-form #:options
	   #:simple-usage #:show-usage #:show-version #:show-help
	   #:sanity-check-option-list))

(in-package #:optparse)

;;;--------------------------------------------------------------------------
;;; Standard error-reporting functions.

(defun moan (msg &rest args)
  "Report an error message in the usual way."
  (format *error-output* "~&~A: ~?~%" *program-name* msg args))
(defun die (&rest args)
  "Report an error message and exit."
  (apply #'moan args)
  (exit 1))

;;;--------------------------------------------------------------------------
;;; The main option parser.

(defstruct (option (:predicate optionp)
		   (:conc-name opt-)
		   (:print-function
		    (lambda (o s k)
		      (declare (ignore k))
		      (format s
	   "#<option~@[ -~C,~]~@[ --~A~]~:[~2*~;~:[=~A~;[=~A]~]~]~@[ ~S~]>"
		              (opt-short-name o)
			      (opt-long-name o)
			      (opt-arg-name o)
			      (opt-arg-optional-p o)
			      (opt-arg-name o)
			      (opt-documentation o))))
		   (:constructor %make-option)
		   (:constructor make-option
				 (long-name
				  short-name
				  &optional
				  arg-name
				  &key
				  (tag (intern (string-upcase long-name)
					       :keyword))
				  negated-tag
				  arg-optional-p
				  doc
				  (documentation doc))))
  "Describes a command-line option.  Slots:

LONG-NAME       The option's long name.  If this is null, the `option' is
                just a banner to be printed in the program's help text.

TAG             The value to be returned if this option is encountered.  If
                this is a function, instead, the function is called with the
                option's argument or nil.

NEGATED-TAG     As for TAG, but used if the negated form of the option is
                found.  If this is nil (the default), the option cannot be
                negated. 

SHORT-NAME      The option's short name.  This must be a single character, or
                nil if the option has no short name.

ARG-NAME        The name of the option's argument, a string.  If this is nil,
                the option doesn't accept an argument.  The name is shown in
                the help text.

ARG-OPTIONAL-P  If non-nil, the option's argument is optional.  This is
                ignored unless ARG-NAME is non-null.

DOCUMENTATION   The help text for this option.  It is automatically
                line-wrapped.  If nil, the option is omitted from the help
                text.

Usually, one won't use make-option, but use the option macro instead."
  (long-name nil :type (or null string))
  (tag nil :type t)
  (negated-tag nil :type t)
  (short-name nil :type (or null character))
  (arg-name nil :type (or null string))
  (arg-optional-p nil :type t)
  (documentation nil :type (or null string)))

(defstruct (option-parser (:conc-name op-)
			  (:constructor make-option-parser
					(argstmp
					 options
					 &key
					 (non-option :skip)
					 ((:numericp numeric-p))
					 negated-numeric-p
					 long-only-p
					 &aux
					 (args (cons nil argstmp))
					 (next args)
					 (negated-p (or negated-numeric-p
							(some
							 #'opt-negated-tag
							 options))))))
  "An option parser object.  Slots:

ARGS            The arguments to be parsed.  Usually this will be
                *command-line-strings*.

OPTIONS         List of option structures describing the acceptable options.

NON-OPTION      Behaviour when encountering a non-option argument.  The
                default is :skip.  Allowable values are:
                  :skip -- pretend that it appeared after the option
                    arguments; this is the default behaviour of GNU getopt
                  :stop -- stop parsing options, leaving the remaining
                    command line unparsed
                  :return -- return :non-option and the argument word

NUMERIC-P       Non-nil tag (as for options) if numeric options (e.g., -43)
                are to be allowed.  The default is nil.  (Anomaly: the
                keyword for this argument is :numericp.)

NEGATED-NUMERIC-P
                Non-nil tag (as for options) if numeric options (e.g., -43)
                can be negated.  This is not the same thing as a negative
                numeric option!

LONG-ONLY-P     A misnomer inherited from GNU getopt.  Whether to allow
                long options to begin with a single dash.  Short options are
                still allowed, and may be cuddled as usual.  The default is
                nil."
  (args nil :type list)
  (options nil :type list)
  (non-option :skip :type (or function (member :skip :stop :return)))
  (next nil :type list)
  (short-opt nil :type (or null string))
  (short-opt-index 0 :type fixnum)
  (short-opt-neg-p nil :type t)
  (long-only-p nil :type t)
  (numeric-p nil :type t)
  (negated-numeric-p nil :type t)
  (negated-p nil :type t))

(define-condition option-parse-error (error simple-condition)
  ()
  (:documentation "Indicates an error found while parsing options.  Probably
not that useful."))

(defun option-parse-error (msg &rest args)
  "Signal an option-parse-error with the given message and arguments."
  (error (make-condition 'option-parse-error
			 :format-control msg
			 :format-arguments args)))

(defun option-parse-remainder (op)
  "Returns the unparsed remainder of the command line."
  (cdr (op-args op)))

(defun option-parse-next (op)
  "The main option-parsing function.  OP is an option-parser object,
initialized appropriately.  Returns two values, OPT and ARG: OPT is the tag
of the next option read, and ARG is the argument attached to it, or nil if
there was no argument.  If there are no more options, returns nil twice.
Options whose TAG is a function aren't returned; instead, the tag function is
called, with the option argument (or nil) as the only argument.  It is safe
for tag functions to throw out of option-parse-next, if they desparately need
to.  (This is the only way to actually get option-parse-next to return a
function value, should that be what you want.)

While option-parse-next is running, there is a restart `skip-option' which
moves on to the next option.  Error handlers should use this to resume after
parsing errors."
  (loop
     (labels ((ret (opt &optional arg)
		(return-from option-parse-next (values opt arg)))
	      (finished ()
		(setf (op-next op) nil)
		(ret nil nil))
	      (peek-arg ()
		(cadr (op-next op)))
	      (more-args-p ()
		(and (op-next op)
		     (cdr (op-next op))))
	      (skip-arg ()
		(setf (op-next op) (cdr (op-next op))))
	      (eat-arg ()
		(setf (cdr (op-next op)) (cddr (op-next op))))
	      (get-arg ()
		(prog1 (peek-arg) (eat-arg)))
	      (process-option (o name negp &key arg argfunc)
		(cond ((not (opt-arg-name o))
		       (when arg
			 (option-parse-error
			  "Option `~A' does not accept arguments"
			  name)))
		      (arg)
		      (argfunc
		       (setf arg (funcall argfunc)))
		      ((opt-arg-optional-p o))
		      ((more-args-p)
		       (setf arg (get-arg)))
		      (t
		       (option-parse-error "Option `~A' requires an argument"
					   name)))
		(let ((how (if negp (opt-negated-tag o) (opt-tag o))))
		  (if (functionp how)
		      (funcall how arg)
		      (ret how arg))))
	      (process-long-option (arg start negp)
		(when (and (not negp)
			   (op-negated-p op)
			   (> (length arg) (+ start 3))
			   (string= arg "no-"
				    :start1 start :end1 (+ start 3)))
		  (incf start 3)
		  (setf negp t))
		(let* ((matches nil)
		       (eqpos (position #\= arg :start start))
		       (len (or eqpos (length arg)))
		       (optname (subseq arg 0 len))
		       (len-2 (- len start)))
		  (dolist (o (op-options op))
		    (cond ((or (not (stringp (opt-long-name o)))
			       (and negp (not (opt-negated-tag o)))
			       (< (length (opt-long-name o)) len-2)
			       (string/= optname (opt-long-name o)
					 :start1 start :end2 len-2)))
			  ((= (length (opt-long-name o)) len-2)
			   (setf matches (list o))
			   (return))
			  (t
			   (push o matches))))
		  (cond ((null matches)
			 (option-parse-error "Unknown option `~A'" optname))
			((cdr matches)
			 (option-parse-error
			  "~
Ambiguous long option `~A' -- could be any of:~{~%  --~A~}"
			  optname
			  (mapcar #'opt-long-name matches))))
		  (process-option (car matches)
				  optname
				  negp
				  :arg (and eqpos
					    (subseq arg (1+ eqpos)))))))
       (with-simple-restart (skip-option "Skip this bogus option.")
	 (cond
	   ;;
	   ;; We're embroiled in short options: handle them.
	   ((op-short-opt op)
	    (if (>= (op-short-opt-index op) (length (op-short-opt op)))
		(setf (op-short-opt op) nil)
		(let* ((str (op-short-opt op))
		       (i (op-short-opt-index op))
		       (ch (char str i))
		       (negp (op-short-opt-neg-p op))
		       (name (format nil "~C~A" (if negp #\+ #\-) ch))
		       (o (find ch (op-options op) :key #'opt-short-name)))
		  (incf i)
		  (setf (op-short-opt-index op) i)
		  (when (or (not o)
			    (and negp (not (opt-negated-tag o))))
		    (option-parse-error "Unknown option `~A'" name))
		  (process-option o
				  name
				  negp
				  :argfunc
				  (and (< i (length str))
				       (lambda ()
					 (prog1
					     (subseq str i)
					   (setf (op-short-opt op)
						 nil))))))))
	   ;;
	   ;; End of the list.  Say we've finished.
	   ((not (more-args-p))
	    (finished))
	   ;;
	   ;; Process the next option.
	   (t
	    (let ((arg (peek-arg)))
	      (cond
		;;
		;; Non-option.  Decide what to do.
		((or (<= (length arg) 1)
		     (and (char/= (char arg 0) #\-)
			  (or (char/= (char arg 0) #\+)
			      (not (op-negated-p op)))))
		 (case (op-non-option op)
		   (:skip (skip-arg))
		   (:stop (finished))
		   (:return (eat-arg)
			    (ret :non-option arg))
		   (t (eat-arg)
		      (funcall (op-non-option op) arg))))
		;;
		;; Double-hyphen.  Stop right now.
		((string= arg "--")
		 (eat-arg)
		 (finished))
		;;
		;; Numbers.  Check these before long options, since `--43' is
		;; not a long option.
		((and (op-numeric-p op)
		      (or (char= (char arg 0) #\-)
			  (op-negated-numeric-p op))
		      (or (and (digit-char-p (char arg 1))
			       (every #'digit-char-p (subseq arg 2)))
			  (and (or (char= (char arg 1) #\-)
				   (char= (char arg 1) #\+))
			       (>= (length arg) 3)
			       (digit-char-p (char arg 2))
			       (every #'digit-char-p (subseq arg 3)))))
		 (eat-arg)
		 (let ((negp (char= (char arg 0) #\+))
		       (num (parse-integer arg :start 1)))
		   (when (and negp (eq (op-negated-numeric-p op) :-))
		     (setf num (- num))
		     (setf negp nil))
		   (let ((how (if negp
				  (op-negated-numeric-p op)
				  (op-numeric-p op))))
		     (if (functionp how)
			 (funcall how num)
			 (ret (if negp :negated-numeric :numeric) num)))))
		;;
		;; Long option.  Find the matching option-spec and process
		;; it.
		((and (char= (char arg 0) #\-)
		      (char= (char arg 1) #\-))
		 (eat-arg)
		 (process-long-option arg 2 nil))
		;;
		;; Short options.  All that's left.
		(t
		 (eat-arg)
		 (let ((negp (char= (char arg 0) #\+))
		       (ch (char arg 1)))
		   (cond ((and (op-long-only-p op)
			       (not (member ch (op-options op)
					    :key #'opt-short-name)))
			  (process-long-option arg 1 negp))
			 (t
			  (setf (op-short-opt op) arg
				(op-short-opt-index op) 1
				(op-short-opt-neg-p op) negp)))))))))))))

(defmacro option-parse-try (&body body)
  "Report errors encountered while parsing options, and continue struggling
along.  Also establishes a restart `stop-parsing'.  Returns t if parsing
completed successfully, or nil if errors occurred."
  (with-gensyms (retcode)
    `(let ((,retcode t))
       (restart-case
	   (handler-bind
	       ((option-parse-error
		 (lambda (cond)
		   (setf ,retcode nil)
		   (moan "~A" cond)
		   (dolist (rn '(skip-option stop-parsing))
		     (let ((r (find-restart rn)))
		       (when r (invoke-restart r)))))))
	     ,@body)
	 (stop-parsing ()
	   :report "Give up parsing options."
	   (setf ,retcode nil)))
       ,retcode)))

(defmacro with-unix-error-reporting ((&key) &body body)
  "Evaluate BODY with errors reported in the standard Unix fashion."
  (with-gensyms (cond)
    `(handler-case
	 (progn ,@body)
       (simple-condition (,cond)
	 (die (simple-condition-format-control ,cond)
	      (simple-condition-format-arguments ,cond)))
       (error (,cond)
	 (die "~A" ,cond)))))

;;;--------------------------------------------------------------------------
;;; Standard option handlers.

(defmacro defopthandler (name (var &optional (arg (gensym)))
			 (&rest args)
			 &body body)
  "Define an option handler function NAME.  Option handlers update a
generalized variable, which may be referred to as VAR in the BODY, based on
some parameters (the ARGS) and the value of an option-argument named ARG."
  (let ((func (intern (format nil "OPTHANDLER/~:@(~A~)" name))))
    `(progn
       (setf (get ',name 'opthandler) ',func)
       (defun ,func (,var ,arg ,@args)
	 (with-locatives ,var
	   (declare (ignorable ,arg))
	   ,@body))
       ',name)))

(defun parse-c-integer (string &key radix (start 0) end)
  "Parse STRING, or at least the parts of it between START and END, according
to the standard C rules.  Well, almost: the 0 and 0x prefixes are accepted,
but so too are 0o (Haskell) and 0b (original); also RADIX_DIGITS is accepted,
for any radix between 2 and 36.  Prefixes are only accepted if RADIX is nil.
Returns two values: the integer parsed (or nil if there wasn't enough for a
sensible parse), and the index following the characters of the integer."
  (unless end (setf end (length string)))
  (labels ((simple (i r goodp sgn)
	     (multiple-value-bind
		 (a i)
		 (if (and (< i end)
			  (digit-char-p (char string i) r))
		     (parse-integer string
				    :start i :end end
				    :radix r
				    :junk-allowed t)
		     (values nil i))
	       (values (if a (* sgn a) (and goodp 0)) i)))
	   (get-radix (i r sgn)
	     (cond (r (simple i r nil sgn))
		   ((>= i end) (values nil i))
		   ((and (char= (char string i) #\0)
			 (>= (- end i) 2))
		    (case (char string (1+ i))
		      (#\x (simple (+ i 2) 16 nil sgn))
		      (#\o (simple (+ i 2) 8 nil sgn))
		      (#\b (simple (+ i 2) 2 nil sgn))
		      (t (simple (1+ i) 8 t sgn))))
		   (t
		    (multiple-value-bind
			(r i)
			(simple i 10 nil +1)
		      (cond ((not r) (values nil i))
			    ((and (< i end)
				  (char= (char string i) #\_)
				  (<= 2 r 36))
			     (simple (1+ i) r nil sgn))
			    (t
			     (values (* r sgn) i))))))))
    (cond ((>= start end) (values nil start))
	  ((char= (char string start) #\-)
	   (get-radix (1+ start) radix -1))
	  ((char= (char string start) #\+)
	   (get-radix (1+ start) radix +1))
	  (t
	   (get-radix start radix +1)))))

(defun invoke-option-handler (handler loc arg args)
  "Call the HANDLER function, giving it LOC to update, the option-argument
ARG, and the remaining ARGS."
  (apply (if (functionp handler) handler
	     (fdefinition (get handler 'opthandler)))
	 loc
	 arg
	 args))

(defopthandler set (var) (&optional (value t))
  "Sets VAR to VALUE; defaults to t."
  (setf var value))
(defopthandler clear (var) (&optional (value nil))
  "Sets VAR to VALUE; defaults to nil."
  (setf var value))
(defopthandler inc (var) (&optional max (step 1))
  "Increments VAR by STEP (defaults to 1), but not greater than MAX (default
nil for no maximum).  No errors are signalled."
  (incf var step)
  (when (>= var max)
    (setf var max)))
(defopthandler dec (var) (&optional min (step 1))
  "Decrements VAR by STEP (defaults to 1), but not less than MIN (default nil
for no maximum).  No errors are signalled."
  (decf var step)
  (when (<= var min)
    (setf var min)))
(defopthandler read (var arg) ()
  "Stores in VAR the Lisp object found by reading the ARG.  Evaluation is
forbidden while reading ARG.  If there is an error during reading, an error
of type option-parse-error is signalled."
  (handler-case
      (let ((*read-eval* nil))
	(multiple-value-bind (x end) (read-from-string arg t)
	  (unless (>= end (length arg))
	    (option-parse-error "Junk at end of argument `~A'" arg))
	  (setf var x)))
    (error (cond)
      (option-parse-error (format nil "~A" cond)))))
(defopthandler int (var arg) (&key radix min max)
  "Stores in VAR the integer read from the ARG.  Integers are parsed
according to C rules, which is normal in Unix; the RADIX may be nil to allow
radix prefixes, or an integer between 2 and 36.  An option-parse-error is
signalled if the ARG is not a valid integer, or if it is not between MIN and
MAX (either of which may be nil if no lower resp. upper bound is wanted)."
  (multiple-value-bind (v end) (parse-c-integer arg :radix radix)
    (unless (and v (>= end (length arg)))
      (option-parse-error "Bad integer `~A'" arg))
    (when (or (and min (< v min))
	      (and max (> v max)))
      (option-parse-error
       "Integer ~A out of range (must have ~@[~D <= ~]x~@[ <= ~D~])"
       arg min max))
    (setf var v)))
(defopthandler string (var arg) ()
  "Stores ARG in VAR, just as it is."
  (setf var arg))
(defopthandler keyword (var arg) (&rest valid)
  (if (null valid)
      (setf var (intern (string-upcase arg) :keyword))
      (let ((matches nil)
	    (guess (string-upcase arg))
	    (len (length arg)))
	(dolist (k valid)
	  (let* ((kn (symbol-name k))
		 (klen (length kn)))
	    (cond ((string= kn guess)
		   (setf matches (list k))
		   (return))
		  ((and (< len klen)
			(string= guess kn :end2 len))
		   (push k matches)))))
	(case (length matches)
	  (0 (option-parse-error "Argument `~A' invalid: must be one of:~
                                   ~{~%~8T~(~A~)~}"
				 arg valid))
	  (1 (setf var (car matches)))
	  (t (option-parse-error "Argument `~A' ambiguous: may be any of:~
                                   ~{~%~8T~(~A~)~}"
				 arg matches))))))
(defopthandler list (var arg) (&optional handler &rest handler-args)
  "Collect ARGs in a list at VAR.  ARGs are translated by the HANDLER first,
if specified.  If not, it's as if you asked for `string'."
  (when handler
    (invoke-option-handler handler (locf arg) arg handler-args))
  (setf var (nconc var (list arg))))

(compile-time-defun parse-option-form (form)
  "Does the heavy lifting for parsing an option form.  See the docstring for
the `option' macro for details of the syntax."
  (flet ((doc (form)
	   (cond ((stringp form) form)
		 ((null (cdr form)) (car form))
		 (t `(format nil ,@form))))
	 (docp (form)
	   (or (stringp form)
	       (and (consp form)
		    (stringp (car form))))))
    (if (and (docp (car form))
	     (null (cdr form)))
	`(%make-option :documentation ,(doc (car form)))
	(let (long-name short-name
			arg-name arg-optional-p
			tag negated-tag
			doc)
	  (dolist (f form)
	    (cond ((and (or (not tag) (not negated-tag))
			(or (keywordp f)
			    (and (consp f)
				 (member (car f) '(lambda function)))))
		   (if tag
		       (setf negated-tag f)
		       (setf tag f)))
		  ((and (not long-name)
			(or (rationalp f)
			    (symbolp f)
			    (stringp f)))
		   (setf long-name (if (stringp f) f
				       (format nil "~(~A~)" f))))
		  ((and (not short-name)
			(characterp f))
		   (setf short-name f))
		  ((and (not doc)
			(docp f))
		   (setf doc (doc f)))
		  ((and (consp f) (symbolp (car f)))
		   (case (car f)
		     (:arg (setf arg-name (cadr f)))
		     (:opt-arg (setf arg-name (cadr f))
			       (setf arg-optional-p t))
		     (:doc (setf doc (doc (cdr f))))
		     (t (let ((handler (get (car f) 'opthandler)))
			  (unless handler
			    (error "No handler `~S' defined." (car f)))
			  (let* ((var (cadr f))
				 (arg (gensym))
				 (thunk `#'(lambda (,arg)
					     (,handler (locf ,var)
							,arg
							,@(cddr f)))))
			    (if tag
				(setf negated-tag thunk)
				(setf tag thunk)))))))
		  (t
		   (error "Unexpected thing ~S in option form." f))))
	  `(make-option ,long-name ,short-name ,arg-name
			,@(and arg-optional-p `(:arg-optional-p t))
			,@(and tag `(:tag ,tag))
			,@(and negated-tag `(:negated-tag ,negated-tag))
			,@(and doc `(:documentation ,doc)))))))

(defmacro options (&rest optlist)
  "More convenient way of initializing options.  The OPTLIST is a list of
OPTFORMS.  Each OPTFORM is either a banner string, or a list of
items.  Acceptable items are interpreted as follows:

  KEYWORD or FUNCTION
    If no TAG is set yet, then as a TAG; otherwise as the NEGATED-TAG.

  STRING (or SYMBOL or RATIONAL)
    If no LONG-NAME seen yet, then the LONG-NAME.  For symbols and rationals,
    the item is converted to a string and squashed to lower-case.

  CHARACTER
     The SHORT-NAME.

  STRING or (STRING STUFF...)
    If no DOCUMENTATION set yet, then the DOCUMENTATION string.  A string is
    used as-is; a list is considered to be a `format' string and its
    arguments.  This is evaluated at standard evaluation time: the option
    structure returned contains a simple documentation string.

  (:ARG NAME)
    Set the ARG-NAME.

  (:OPT-ARG NAME)
    Set the ARG-NAME, and also set ARG-OPTIONAL-P.

  (HANDLER VAR ARGS...)
    If no TAG is set yet, attach the HANDLER to this option, giving it ARGS.
    Otherwise, set the NEGATED-TAG."
  `(list ,@(mapcar (lambda (form)
		     (if (stringp form)
			 `(%make-option :documentation ,form)
			 (parse-option-form form)))
		   optlist)))

;;;--------------------------------------------------------------------------
;;; Support stuff for help and usage messages

(defun print-text (string
		   &optional
		   (stream *standard-output*)
		   &key
		   (start 0)
		   (end nil))
  "Prints STRING to a pretty-printed STREAM, breaking it at whitespace and
newlines in the obvious way.  Stuff between square brackets is not broken:
this makes usage messages work better."
  (let ((i start)
	(nest 0)
	(splitp nil))
    (flet ((emit ()
	     (write-string string stream :start start :end i)
	     (setf start i)))
      (unless end
	(setf end (length string)))
      (loop
	 (unless (< i end)
	   (emit)
	   (return))
	 (let ((ch (char string i)))
	   (cond ((char= ch #\newline)
		  (emit)
		  (incf start)
		  (pprint-newline :mandatory stream))
		 ((whitespace-char-p ch)
		  (when (zerop nest)
		    (setf splitp t)))
		 (t
		  (when splitp
		    (emit)
		    (pprint-newline :fill stream))
		  (setf splitp nil)
		  (case ch
		    (#\[ (incf nest))
		    (#\] (when (plusp nest) (decf nest))))))
	   (incf i))))))

(defun simple-usage (opts &optional mandatory-args)
  "Build a simple usage list from a list of options, and (optionally)
mandatory argument names."
  (let (short-simple long-simple short-arg long-arg)
    (dolist (o opts)
      (cond ((not (and (opt-documentation o)
		       (opt-long-name o))))
	    ((and (opt-short-name o) (opt-arg-name o))
	     (push o short-arg))
	    ((opt-short-name o)
	     (push o short-simple))
	    ((opt-arg-name o)
	     (push o long-arg))
	    (t
	     (push o long-simple))))
    (list
     (nconc (and short-simple
		 (list (format nil "[-~{~C~}]"
			       (sort (mapcar #'opt-short-name short-simple)
				     #'char<))))
	    (and long-simple
		 (mapcar (lambda (o)
			   (format nil "[--~A]" (opt-long-name o)))
			 (sort long-simple #'string< :key #'opt-long-name)))
	    (and short-arg
		 (mapcar (lambda (o)
			   (format nil "~:[[-~C ~A]~;[-~C[~A]]~]"
				   (opt-arg-optional-p o)
				   (opt-short-name o)
				   (opt-arg-name o)))
			 (sort short-arg #'char-lessp
			       :key #'opt-short-name)))
	    (and long-arg
		 (mapcar (lambda (o)
			   (format nil "~:[[--~A ~A]~;[--~A[=~A]]~]"
				   (opt-arg-optional-p o)
				   (opt-long-name o)
				   (opt-arg-name o)))
			 (sort long-arg #'string-lessp
			       :key #'opt-long-name)))
	    (listify mandatory-args)))))

(defun show-usage (prog usage &optional (stream *standard-output*))
  "Basic usage-showing function.  PROG is the program name, probable from
*command-line-strings*.  USAGE is a list of possible usages of the program,
each of which is a list of items to be supplied by the user.  In simple
cases, a single string is sufficient."
  (pprint-logical-block (stream nil :prefix "Usage: ")
    (dolist (u (listify usage))
      (pprint-logical-block (stream nil :prefix (format nil "~A " prog))
	(format stream "~{~A ~:_~}" (listify u)))
      (pprint-newline :mandatory stream))))

(defun show-help (prog ver usage opts &optional (stream *standard-output*))
  "Basic help-showing function.  PROG is the program name, probably from
*command-line-strings*.  VER is the program's version number.  USAGE is a
list of the possible usages of the program, each of which may be a list of
items to be supplied.  OPTS is the list of supported options, as provided to
the options parser.  STREAM is the stream to write on."
  (format stream "~A, version ~A~2%" prog ver)
  (show-usage prog usage stream)
  (terpri stream)
  (let (newlinep)
    (dolist (o opts)
      (let ((doc (opt-documentation o)))
	(cond ((not o))
	      ((not (opt-long-name o))
	       (when newlinep
		 (terpri stream)
		 (setf newlinep nil))
	       (pprint-logical-block (stream nil)
		 (print-text doc stream))
	       (terpri stream))
	      (t
	       (setf newlinep t)
	       (pprint-logical-block (stream nil :prefix "  ")
		 (pprint-indent :block 30 stream)
		 (format stream "~:[   ~;-~:*~C,~] --~A"
			 (opt-short-name o)
			 (opt-long-name o))
		 (when (opt-arg-name o)
		   (format stream "~:[=~A~;[=~A]~]"
			   (opt-arg-optional-p o)
			   (opt-arg-name o)))
		 (write-string "  " stream)
		 (pprint-tab :line 30 1 stream)
		 (print-text doc stream))
	       (terpri stream)))))))

(defun sanity-check-option-list (opts)
  "Check the option list OPTS for basic sanity.  Reused short and long option
names are diagnosed.  Maybe other problems will be reported later.  Returns a
list of warning strings."
  (let ((problems nil)
	(longs (make-hash-table :test #'equal))
	(shorts (make-hash-table)))
    (flet ((problem (msg &rest args)
	     (push (apply #'format nil msg args) problems)))
      (dolist (o opts)
	(push o (gethash (opt-long-name o) longs))
	(push o (gethash (opt-short-name o) shorts)))
      (maphash (lambda (k v)
		 (when (and k (cdr v))
		   (problem "Long name `--~A' reused in ~S" k v)))
	       longs)
      (maphash (lambda (k v)
		 (when (and k (cdr v))
		   (problem "Short name `-~C' reused in ~S" k v)))
	       shorts)
      problems)))

;;;----- That's all, folks --------------------------------------------------