fp1/week1/mart/MatchStrings.icl

   1 implementation module MatchStrings
   2
   3 import StdEnv
   4
   5 head :: String -> Char
   6 head "" = abort "Empty String"
   7 head s = s.[0]
   8
   9 tail :: String -> String
  10 tail "" = abort "Empty String"
  11 tail s = s % (1, size s - 1)
  12
  13 is_gelijk :: String String -> Bool
  14 is_gelijk "" "" = True
  15 is_gelijk a b = (size a == size b) && (head a == head b) && is_gelijk (tail a) (tail b)
  16
  17 is_deelstring :: String String -> Bool
  18 is_deelstring _ "" = False
  19 is_deelstring a b = is_begin a b || is_deelstring a (tail b)
  20
  21 is_begin :: String String -> Bool
  22 is_begin "" _ = True
  23 is_begin _ "" = False
  24 is_begin a b = head a == head b && is_begin (tail a) (tail b)
  25
  26 is_deel :: String String -> Bool
  27 is_deel "" _ = True
  28 is_deel _ "" = False
  29 is_deel a b = head a == head b && is_deel (tail a) (tail b) || is_deel a (tail b)
  30
  31 is_match :: String String -> Bool
  32 is_match a b = is_begin_match a b || size b > 0 && is_begin_match a (tail b)
  33
  34 is_begin_match :: String String -> Bool
  35 is_begin_match "" _ = True
  36 is_begin_match a "" = head a == '*' && size a == 1
  37 is_begin_match a b
  38 | head a == '.' || head a == head b = is_begin_match (tail a) (tail b)
  39 | head a == '*' = is_begin_match a (tail b) || is_begin_match (tail a) b
  40 | otherwise = False
  41
  42 //Start= (head pink_floyd, tail pink_floyd)
  43 //Start= is_gelijk     "" " "
  44 //Start= is_deelstring "there"          pink_floyd
  45 //Start= is_deelstring "there"          marillion
  46 //Start= is_deel       "there"          marillion
  47 //Start= is_deel       "she and her"    pink_floyd
  48 //Start= is_deel       radiohead        pink_floyd
  49 //Start= is_match      "*.here*.here*." pink_floyd
  50 //Start= is_match      ".here.here."    pink_floyd
  51
  52 pink_floyd= "Is there anybody in there?"
  53 marillion= "Just for the record"
  54 radiohead= "There there"