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+#! /home/dat/mira/states/src/miranda/mira -exec
+|| Contributed by John Cupitt, University of Kent
+
+||A while ago Steve Hill (I think) appealed for useful Miranda programs
+||-- well, here is the greatest productivity aid for Miranda hackers
+||since ball-point pens.  A 'vi' type filter to *rebox your comments*!!
+||Amazing. It turns dull, unexciting notes like:
+
+|| Given a node in the tree,
+||examine the branches and chose the exit with the
+|| highest score.
+
+||into:
+
+||----------------------------------------------------------------------||
+|| Given a node in the tree, examine the branches and chose the exit 	||
+|| with the highest score.						||
+||----------------------------------------------------------------------||
+
+||Any comments welcome -- my Miranda is not as hot as it could be ...
+
+||John
+
+||----------------------------------------------------------------------||
+|| Box up Miranda comments. A filter from stdin to stdout
+||	do_box :: [char] -> [char]					||
+||		- Strip ||s, reformat, rebox.				||
+||----------------------------------------------------------------------||
+
+main = [Stdout (do_box $-)]
+
+||----------------------------------------------------------------------||
+|| Reboxing done in a pipeline of five stages.				||
+||	- Split the input into lines					||
+||	- Strip '||'s from input					||
+||	- Lex the input, breaking into tokens				||
+||	- Rejig tokens to produce fmted type output			||
+||	- Output tokens as [char] with a box drawn around them		||
+|| Formatting rules:							||
+||	- Lines starting '||-' are deleted				||
+||	- Leading & trailing '||' removed				||
+||	- Lines starting with a tab are not reformatted			||
+||	- Blank lines are 'new paragraph'				||
+||----------------------------------------------------------------------||
+
+||----------------------------------------------------------------------||
+|| First a few types and useful little functions.			||
+||----------------------------------------------------------------------||
+
+|| Useful constants
+outWid = 68			|| Width of the text in our boxes
+boxWid = 72			|| Size of the box we draw
+
+|| A token
+tok ::=	Word [char] | Newpara | Line [char]
+
+|| Useful character classifier
+whitespace :: char -> bool
+whitespace ch
+      =	True, if ch = '\n' \/ ch = '\t' \/ ch = ' '
+      =	False, otherwise
+
+|| An edge of a box boxWid across
+edge :: [char]
+edge  =	"||" ++ (rep (boxWid-2) '-') ++ "||\n"
+
+|| Find the length of a line containing tabs
+len :: [char] -> num
+len str
+      = len' 0 str
+	where
+	len' n []
+	      = n
+	len' n (a:rest)
+	      =	len' (n+tab_space) rest, if a = '\t'
+	      =	len' (n+1) rest, otherwise
+		where
+		tab_space
+		      =	8 - (n mod 8)
+
+|| Useful when doing output --- only attach first param if its not [].
+no_blank :: [char] -> [[char]] -> [[char]]
+no_blank a b
+      = a : b, if a ~= []
+      = b, otherwise
+
+||----------------------------------------------------------------------||
+|| The main function. Call from a shell script in your /bin directory	||
+|| looking something like:						||
+||	#! /usr/bin/mira -exec						||
+||	main = [Stdout (do_box $-)]					||
+||	%include "../mira/box/box.m"					||
+||----------------------------------------------------------------------||
+
+do_box :: [char] -> [char]
+do_box input
+      =	edge ++ rejig input ++ edge
+	where
+	rejig =	re_box . format . lex_start . strip_start . split
+
+||----------------------------------------------------------------------||
+|| The first stage in processing. Split the input [char] into lines as	||
+|| [[char]].								||
+||----------------------------------------------------------------------||
+
+|| Split the text into a list of lines
+split :: [char] -> [[char]]
+split input
+      =	split' [] input
+	where
+	split' sofar (a:input)
+	      =	sofar : split input, if a = '\n'
+	      = split' (sofar ++ [a]) input, otherwise
+	split' sofar []
+	      = no_blank sofar []			|| No extra blank lines!
+
+||----------------------------------------------------------------------||
+|| The next stage ... strip old '||'s from the input. Remove:		||
+||	- Lines starting '||-'						||
+||	- Strip leading '||'s						||
+||	- Strip trailing '||'s & trailing spaces			||
+||----------------------------------------------------------------------||
+
+|| At the start of a line:
+strip_start :: [[char]] -> [[char]]
+strip_start ([]:input)
+      =	[] : strip_start input			|| Keep blank lines
+strip_start (('|':'|':line):input)
+      = strip_start' line
+	where
+	strip_start' ('-':rest)
+	      = strip_start input		|| Strip '||---||' lines
+	strip_start' rest
+	      =	strip_rest rest input		|| Strip leading '||'
+strip_start (line:input)
+      = strip_rest line input			|| Pass rest through
+strip_start []
+      = []
+
+|| Scan along the rest of the line looking for trailing '||'s to strip.
+strip_rest :: [char] -> [[char]] -> [[char]]
+strip_rest line input
+      =	strip_rest' (rev line) input
+	where
+	strip_rest' ('|':'|':rest) input
+	      =	strip_rest' rest input			|| Strip trailing ||
+	strip_rest' (x:rest) input
+	      = strip_rest' rest input, if whitespace x
+	strip_rest' line input
+	      =	(rev line) : strip_start input
+
+|| Efficient(ish) reverse
+rev list
+      =	rev' [] list
+	where
+	rev' sofar (a:x)
+	      =	rev' (a:sofar) x
+	rev' sofar []
+	      = sofar
+
+||----------------------------------------------------------------------||
+|| The next stage ... Break the input into Word, Newpara and Line	||
+|| tokens. Newpara for blank lines and line starting with space; Line	||
+|| for lines starting with a tab.					||
+||----------------------------------------------------------------------||
+
+|| At the start of a line.
+lex_start :: [[char]] -> [tok]
+lex_start ([]:input)
+      = Newpara : lex_start input		|| Preserve blank lines
+lex_start (('\t':rest):input)
+      =	Line ('\t':rest) : lex_start input	|| Don't format tab lines
+lex_start (line:input)
+      = lex_rest (strip_ws line) input		|| Lex to eol
+lex_start []
+      =	[]
+
+|| In the middle of a line. Try to take words off the front of what we
+|| have so far. 
+lex_rest :: [char] -> [[char]] -> [tok]
+lex_rest [] input
+      =	lex_start input
+lex_rest sofar input
+      =	Word wd : lex_rest (strip_ws rest) input
+	where
+	(wd, rest)
+	      =	break_word sofar
+
+|| Strip ws from the start of the line
+strip_ws (a:input)
+      =	(a:input), if ~whitespace a
+      = strip_ws input, otherwise
+strip_ws []
+      =	[]
+
+|| Break the word from the front of a line of text. Return the remains
+|| of the line along with the word.
+break_word :: [char] -> ([char], [char])
+break_word (a:line)
+      =	([a] ++ rest, tag), if ~whitespace a
+      =	([], (a:line)), otherwise
+	where
+	(rest, tag)
+	      =	break_word line
+break_word []
+      =	([],[])
+
+||----------------------------------------------------------------------||
+|| Almost the last stage ... Turn [tok] back into [[char]]. Format	||
+|| onto outWid character lines.						||
+||----------------------------------------------------------------------||
+
+format :: [tok] -> [[char]]
+format input
+      =	format' [] input
+	where
+	format' sofar (Word wd:rest)
+	      =	format' (sofar ++ " " ++ wd) rest, if #sofar + #wd < outWid
+	      = sofar : format' (" " ++ wd) rest, otherwise
+	format' sofar (Newpara:rest)
+	      = no_blank sofar ([] : format rest)
+	format' sofar (Line line:rest)
+	      = no_blank sofar (line : format rest)
+	format' sofar []
+	      = no_blank sofar []
+
+||----------------------------------------------------------------------||
+|| The final stage. Box up a list of formatted lines. Try to be clever	||
+|| about using tabs on the ends of lines.				||
+||----------------------------------------------------------------------||
+
+|| Draw a box boxWid across.
+re_box :: [[char]] -> [char]
+re_box (line:rest)
+      =	"||" ++ line ++ padding ++ "||\n" ++ (re_box rest)
+	where
+	padding
+	      =	rep n_tab '\t'
+	n_tab
+	      =	(boxWid - line_length + 7) div 8
+	line_length
+	      =	len ("||" ++ line)
+re_box []
+      =[]