first part of part 1 of exercise 7

1 files changed, 21 insertions, 7 deletions

diff --git a/AufgabeFFP7.hs b/AufgabeFFP7.hs
index 8f2a7c8..c9454a5 100644
--- a/AufgabeFFP7.hs
+++ b/AufgabeFFP7.hs
@@ -8,25 +8,39 @@ import Test.QuickCheck
 type Buffer = (Int, String)
 
 -- the empty buffer
---TODO empty :: Buffer
+empty :: Buffer
+empty = (0, "")
 
 -- insert character before cursor
---TODO insert :: Char -> Buffer -> Buffer
+insert :: Char -> Buffer -> Buffer
+insert c (cur, buf) = (cur, buf1 ++ [c] ++ buf2)
+  where
+    (buf1, buf2) = splitAt cur buf
 
 -- delete character before cursor
---TODO delete :: Buffer -> Buffer
+delete :: Buffer -> Buffer
+delete (cur, buf)
+  | buf2 == [] = (min cur (length buf1), buf1)
+  | cur < 0 = (cur, buf)
+  | otherwise = (cur, buf1 ++ tail buf2)
+  where
+    (buf1, buf2) = splitAt cur buf
 
 -- move cursor left one character
---TODO left :: Buffer -> Buffer
+left :: Buffer -> Buffer
+left (cur, buf) = (min (length buf) (max (cur - 1) 0), buf)
 
 -- move cursor right one character
---TODO right :: Buffer -> Buffer
+right :: Buffer -> Buffer
+right (cur, buf) = (max 0 (min (cur + 1) (length buf)), buf)
 
 -- is cursor at left end?
---TODO atLeft :: Buffer -> Bool
+atLeft :: Buffer -> Bool
+atLeft (cur, buf) = cur == 0
 
 -- is cursor at right end?
---TODO atRight :: Buffer -> Bool
+atRight :: Buffer -> Bool
+atRight (cur, buf) = cur == length buf
 
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