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+||Text formatting program (DT)
+||Reformats text to a specified width, with line-fill
+
+%export just 
+
+||To try this out from within a Miranda session, say e.g.
+||	just 60 (read "file")
+||where "file" contains some text you want to reformat.
+
+||You could also make it into a UNIX filter -- see the example `mrev'.
+
+||----------------------------------------------------------------------||
+|| in this program we move between three different representations of	||
+|| text - as a flat list of characters, including spaces and newlines	||
+|| - as a list of lines (containing spaces but not newlines)            ||
+|| - and as a list of list of words.					||
+||----------------------------------------------------------------------||
+
+text == [char]
+line == [char]
+word == [char]
+
+just::num->text->text  ||the main function
+just n = concat.map(reformat n).paras.map words.lines
+
+||lines::text->[line]
+||lines is defined in <stdenv> - it breaks a string into lines,
+||removing the newline characters
+
+paras::[[word]]->[[word]]
+||make each paragraph into one long line, by joining adjacent 
+||non-blank lines
+paras (a:b:x) = paras ((a++b):x), if a~=[]~=b
+              = a:paras (b:x), otherwise
+paras (a:[]) = a:[]
+paras [] = []
+
+reformat::num->[word]->text
+||reformat a paragraph to width n
+reformat n [] = "\n"  ||the empty paragraph represents a blank line
+reformat n x = lay(justify n (partition n x))
+
+||lay::[line]->text
+||lay is defined in <stdenv> - it is the inverse of lines
+
+justify::num->[[word]]->[line]
+justify n para = map(fill_line n)(init para)++[unwords(last para)]
+
+partition::num->[word]->[[word]]
+||break a paragraph into lines, with as many words as will fit in width
+||n on each line (except the last)
+partition n [] = []
+partition n x  = x1 : partition n rest
+		 where
+		 (x1,rest) = grab [] x
+		 grab y (w:x) = grab (w:y) x, if sum(map(#)y)+#y+#w <= n
+			      = (reverse y,w:x), otherwise
+		 grab y [] = (reverse y,[])
+
+fill_line :: num->[word]->line
+||make words into a line of length n exactly, by inserting enough spaces
+fill_line n words 
+    = (concat.concat) (transpose [words,mkspaces (w-1) (n-sw)])
+      where
+      w = #words
+      sw = sum(map (#) words)
+
+mkspaces :: num->num->[[char]]
+||return s spaces broken into n groups
+mkspaces n s = map f [1..n], if n mod 2=0  ||see note
+	     = map f [n,n-1..1], otherwise
+               where
+	       f i = rep (s div n + delta) ' '
+		     where
+		     delta = 1, if i<=s mod n
+			   = 0, otherwise
+||note: we put the extra spaces in sometimes from the left and sometimes 
+||from the right, depending on the parity of n.  This is to avoid 
+||visually unbalancing the text by having all the extra spaces towards
+||one margin.  Using the parity of n to decide this is arbitrary.
+
+words :: line->[word]
+||break a line into words
+words = filter (~=[]) . foldr (breakon ' ') [[]]
+
+unwords :: [word]->line
+||join words to make a line, inserting one space as separator
+unwords = foldr1 (insert ' ')
+
+insert :: *->[*]->[*]->[*]
+insert a x y = x ++ [a] ++ y
+
+breakon :: *->*->[[*]]->[[*]]
+breakon c a x = []:x, if a=c
+	      = (a:hd x):tl x, otherwise
+
+||These definitions of `words' and `unwords' are due to Richard Bird,  see
+||Bird and Wadler (1988), page 91.