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  1. import Data.Char
  2. import Data.List
  3.  
  4. digitRangeToRegex :: Integer -> Integer -> String
  5. digitRangeToRegex min max
  6.     | min == max = digit min : ""
  7. -- uncomment if you want \d instead of [0-9]
  8. --    | min == 0 && max == 9 = "\\d"
  9.     | min >= 10 || max <= 9 = "[" ++ rangeToStr (digit min) (digit max) ++ "]"
  10.     | otherwise = "[" ++ rangeToStr (digit min) '9' ++ rangeToStr 'a' (digit max) ++ "]"
  11.     where
  12.         rangeToStr min max
  13.             | min == max = min : ""
  14.             | otherwise = min : '-' : max : ""
  15.         digit d
  16.             | d >= 0 && d <= 9 = chr (ord '0' + fromIntegral d)
  17.             | d < 36 = chr (ord 'a' + fromIntegral d - 10)
  18.  
  19. numberRangeToRegex :: Integer -> Integer -> Integer -> String
  20. numberRangeToRegex base min max
  21.     | min == 0 && max == 0 = "0"
  22.     | cmin == cmax = intercalate "|" $ map formatRanges $ step dmin dmax
  23.     | otherwise = intercalate "|" $
  24.         (map formatRanges $ step dmin (replicate cmin (base-1))) ++
  25.         (if cmin + 1 < cmax then [digitRangeToRegex 1 (base - 1) ++ digitRangeToRegex 0 (base-1) ++ formatCount cmin (cmax-2)] else []) ++
  26.         (map formatRanges $ step (1 : replicate (cmax-1) 0) dmax)
  27.     where
  28.         digits 0 = [0]
  29.         digits n = reverse $ map (`mod` base) $ takeWhile (>0) $ iterate (`div` base) n
  30.         dmin = digits min
  31.         dmax = digits max
  32.         cmin = length dmin
  33.         cmax = length dmax
  34.         step [] [] = [[]]
  35.         step (a:as) (b:bs) =
  36.             if a == b then
  37.                 prepend a $ step as bs
  38.             else
  39.                 (if zeroHead then [] else prepend a $ step as nines) ++
  40.                 (if na > nb then [] else [(na, nb) : replicate (length as) (0, base-1)]) ++
  41.                 (if nineTail then [] else prepend b $ step zeros bs)
  42.             where
  43.                 suffixLen = length as
  44.                 zeroHead = all (== 0) as
  45.                 nineTail = all (== base-1) bs
  46.                 na = if zeroHead then a else a+1
  47.                 nb = if nineTail then b else b-1
  48.                 zeros = replicate suffixLen 0
  49.                 nines = replicate suffixLen (base-1)
  50.                 prepend x = map ((x, x):)
  51.         formatRanges = concatMap formatGroup . group . dropWhile (== (0,0)) where
  52.             formatGroup [(min, max)] = digitRangeToRegex min max
  53.             formatGroup xs@((min, max) : _)
  54.                 | min == max = concat $ replicate (length xs) $ digitRangeToRegex min max
  55.                 | otherwise = digitRangeToRegex min max ++ "{" ++ show (length xs) ++ "}"
  56.         formatCount min max
  57.             | min == 1 && max == 1 = ""
  58.             | min == max = "{" ++ show min ++ "}"
  59.             | otherwise = "{" ++ show min ++ "," ++ show max ++ "}"
  60.  
  61. main = putStrLn $ numberRangeToRegex 10 42 100500
Success #stdin #stdout 0s 6240KB
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stdin
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Standard input is empty
stdout
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4[2-9]|[5-9][0-9]|[1-9][0-9]{2,4}|100[0-4][0-9]{2}|100500
https://ideone.com/FzAmYd
language:
Haskell (ghc 8.4.4)
created:
13 years ago
visibility:
secret

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