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| -rw-r--r-- | README.md | 2 | ||||
| -rw-r--r-- | ch08/8_a_2.hs | 109 |
2 files changed, 110 insertions, 1 deletions
@@ -107,7 +107,7 @@ of a group is in bold italics. | **_6_a_1_** | yes | 162 | 6. Using typeclasses | | 6_a_2 | yes | | | | **_8_a_1_** | yes | 205 | 8. Efficient file processing, regular expressions, and file name matching | -| 8_a_2 | | | | +| 8_a_2 | yes | | | | **_8_b_1_** | | 210 | | | 8_b_2 | | | | | 8_b_3 | | | | diff --git a/ch08/8_a_2.hs b/ch08/8_a_2.hs new file mode 100644 index 0000000..92f130a --- /dev/null +++ b/ch08/8_a_2.hs @@ -0,0 +1,109 @@ +-- While filesystems on Unix are usually case-sensitive (e.g. “G” vs. “g”) in +-- file names, Windows filesystems are not. Add a parameter to the globToRegex +-- and matchesGlob functions that allows control over case sensitive matching. + +-- For simplicity, let's assume that only a-z and A-Z letters are affected by +-- the case sensitivity option. Also, probably not all error cases are detected +-- when converting a glob to regex. + +{-- From examples/examples/ch08/GlobRegex.hs modified according to the assignment --} +import Data.Char +import Text.Regex.Posix ((=~)) + +data MatchOptions = DontIgnoreCase | IgnoreCase + +globToRegex :: String -> MatchOptions -> String +globToRegex cs opt = '^' : globToRegex' cs opt ++ "$" + +globToRegex' :: String -> MatchOptions -> String +globToRegex' "" _ = "" +globToRegex' ('*':cs) opt = ".*" ++ globToRegex' cs opt +globToRegex' ('?':cs) opt = '.' : globToRegex' cs opt +globToRegex' ('[':'!':cs) opt = "[^" ++ charClass cs opt +globToRegex' ('[':cs) opt = '[' : charClass cs opt +globToRegex' (c:cs) opt = escape c opt ++ globToRegex' cs opt + +escape :: Char -> MatchOptions -> String +escape c opt | c `elem` regexChars = '\\' : [c] + | otherwise = caseOutsideCharClass c opt + where regexChars = "\\+()^$.{}]|" + +charClass :: String -> MatchOptions -> String +charClass (']':cs) opt = ']' : globToRegex' cs opt +charClass (a:'-':c:cs) opt = caseRange a c opt ++ charClass cs opt +charClass (c:cs) opt = (caseInsideCharClass c opt) ++ charClass cs opt +charClass [] _ = error "unterminated character class" + + +matchesGlob :: FilePath -> String -> MatchOptions -> Bool +matchesGlob name pat opt = name =~ (globToRegex pat opt) +{-- End of code from examples --} + +oppositeCase :: Char -> Char +oppositeCase c = if isAlpha c + then if isLower c + then toUpper c + else toLower c + else error (c:" is not a caseable character") + +caseRange :: Char -> Char -> MatchOptions -> String +caseRange a c DontIgnoreCase = a : '-' : [c] +caseRange a c IgnoreCase = if sameCase + then a:'-':c:opA:'-':[opC] + -- Patterns like W-d which means W-Za-d are + -- converted like w-za-dW-ZA-D + else opA:"-za-" ++ c:a:"-ZA-" ++ [opC] + where sameCase = ((isLower a) && (isLower c)) || ((isUpper a) && (isUpper c)) + opA = oppositeCase a + opC = oppositeCase c + +caseInsideCharClass :: Char -> MatchOptions -> String +caseInsideCharClass c DontIgnoreCase = [c] +caseInsideCharClass c IgnoreCase = if isAlpha c + then (oppositeCase c) : [c] + else [c] + +caseOutsideCharClass :: Char -> MatchOptions -> String +caseOutsideCharClass c DontIgnoreCase = [c] +caseOutsideCharClass c opt = if shouldBeInBrackets + then '[' : cased ++ "]" + else cased + where cased = caseInsideCharClass c opt + shouldBeInBrackets = (length cased) > 1 + +-- ghci> :l 8_a_2.hs +-- [1 of 1] Compiling Main ( 8_a_2.hs, interpreted ) +-- Ok, one module loaded. + +-- ghci> globToRegex "f[o-1].c" IgnoreCase +-- "^[Ff][O-za-1o-ZA-*** Exception: 1 is not a caseable character +-- CallStack (from HasCallStack): +-- error, called at 8_a_2.hs:48:23 in main:Main + +-- ghci> globToRegex "f[gH,i-kL-N]*.c" DontIgnoreCase +-- "^f[gH,i-kL-N].*\\.c$" +-- ghci> matchesGlob "fhjM.c" "f[gH,i-kL-N]*.c" DontIgnoreCase +-- False +-- ghci> matchesGlob "fHjM.c" "f[gH,i-kL-N]*.c" DontIgnoreCase +-- True + +-- ghci> globToRegex "f[gH,i-kL-N]*.c" IgnoreCase +-- "^[Ff][GghH,i-kI-KL-Nl-n].*\\.[Cc]$" +-- ghci> matchesGlob "fhjM.c" "f[gH,i-kL-N]*.c" IgnoreCase +-- True +-- ghci> matchesGlob "fGhJm.c" "f[gH,i-kL-N]*.c" IgnoreCase +-- True + +-- ghci> globToRegex "f[W-d]*.c" DontIgnoreCase +-- "^f[W-d].*\\.c$" +-- ghci> matchesGlob "fxa.c" "f[W-d]*.c" DontIgnoreCase +-- False +-- ghci> matchesGlob "fXa.c" "f[W-d]*.c" DontIgnoreCase +-- True + +-- ghci> globToRegex "f[W-d]*.c" IgnoreCase +-- "^[Ff][w-za-dW-ZA-D].*\\.[Cc]$" +-- ghci> matchesGlob "fwa.c" "f[W-d]*.c" IgnoreCase +-- True +-- ghci> matchesGlob "fXawD.c" "f[W-d]*.c" IgnoreCase +-- True |