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-- | Part of this code is from "Report on the Programming Language Haskell",
-- version 1.2, appendix C.
module Language.Preprocessor.Unlit (unlit) where
import Data.Char
import Data.List (isPrefixOf)
data Classified = Program String | Blank | Comment
| Include Int String | Pre String
classify :: [String] -> [Classified]
classify [] = []
classify (('\\':x):xs) | x == "begin{code}" = Blank : allProg xs
where allProg [] = [] -- Should give an error message,
-- but I have no good position information.
allProg (('\\':x):xs) | "end{code}"`isPrefixOf`x = Blank : classify xs
allProg (x:xs) = Program x:allProg xs
classify (('>':x):xs) = Program (' ':x) : classify xs
classify (('#':x):xs) = (case words x of
(line:rest) | all isDigit line
-> Include (read line) (unwords rest)
_ -> Pre x
) : classify xs
classify (x:xs) | all isSpace x = Blank:classify xs
classify (x:xs) = Comment:classify xs
unclassify :: Classified -> String
unclassify (Program s) = s
unclassify (Pre s) = '#':s
unclassify (Include i f) = '#':' ':show i ++ ' ':f
unclassify Blank = ""
unclassify Comment = ""
-- | 'unlit' takes a filename (for error reports), and transforms the
-- given string, to eliminate the literate comments from the program text.
unlit :: FilePath -> String -> String
unlit file lhs = (unlines
. map unclassify
. adjacent file (0::Int) Blank
. classify) (inlines lhs)
adjacent :: FilePath -> Int -> Classified -> [Classified] -> [Classified]
adjacent file 0 _ (x :xs) = x : adjacent file 1 x xs -- force evaluation of line number
adjacent file n y@(Program _) (x@Comment :xs) = error (message file n "program" "comment")
adjacent file n y@(Program _) (x@(Include i f):xs) = x: adjacent f i y xs
adjacent file n y@(Program _) (x@(Pre _) :xs) = x: adjacent file (n+1) y xs
adjacent file n y@Comment (x@(Program _) :xs) = error (message file n "comment" "program")
adjacent file n y@Comment (x@(Include i f):xs) = x: adjacent f i y xs
adjacent file n y@Comment (x@(Pre _) :xs) = x: adjacent file (n+1) y xs
adjacent file n y@Blank (x@(Include i f):xs) = x: adjacent f i y xs
adjacent file n y@Blank (x@(Pre _) :xs) = x: adjacent file (n+1) y xs
adjacent file n _ (x@next :xs) = x: adjacent file (n+1) x xs
adjacent file n _ [] = []
message :: String -> Int -> String -> String -> String
message "\"\"" n p c = "Line "++show n++": "++p++ " line before "++c++" line.\n"
message [] n p c = "Line "++show n++": "++p++ " line before "++c++" line.\n"
message file n p c = "In file " ++ file ++ " at line "++show n++": "++p++ " line before "++c++" line.\n"
-- Re-implementation of 'lines', for better efficiency (but decreased laziness).
-- Also, importantly, accepts non-standard DOS and Mac line ending characters.
inlines :: String -> [String]
inlines s = lines' s id
where
lines' [] acc = [acc []]
lines' ('\^M':'\n':s) acc = acc [] : lines' s id -- DOS
lines' ('\^M':s) acc = acc [] : lines' s id -- MacOS
lines' ('\n':s) acc = acc [] : lines' s id -- Unix
lines' (c:s) acc = lines' s (acc . (c:))
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