Defined a show instance for Octet.

[hath.git] / src / Octet.hs

diff --git a/src/Octet.hs b/src/Octet.hs
index 28d3d7d5feb3b8e4165122ea2e689c5b1bf6e1e5..bdada65ab1b8e11bb52d95bdf33a7a25d4ce751c 100644 (file)
--- a/src/Octet.hs
+++ b/src/Octet.hs
@@ -5,15 +5,21 @@ import Bit
 -- An Octet consists of eight bits. For our purposes, the most
 -- significant bit will come "first." That is, b1 is in the 2^7
 -- place while b8 is in the 2^0 place.
-data Octet = Octet { b1 :: Bit,
-                     b2 :: Bit,
-                     b3 :: Bit,
-                     b4 :: Bit,
-                     b5 :: Bit,
-                     b6 :: Bit,
-                     b7 :: Bit,
-                     b8 :: Bit }
-           deriving (Eq, Show)
+data Octet = None | Octet { b1 :: Bit,
+                            b2 :: Bit,
+                            b3 :: Bit,
+                            b4 :: Bit,
+                            b5 :: Bit,
+                            b6 :: Bit,
+                            b7 :: Bit,
+                            b8 :: Bit }
+           deriving (Eq)
+
+
+instance Show Octet where
+    show Octet.None = "None"
+    show oct = show (octet_to_int oct)
+
 
 -- Convert each bit to its integer value, and multiply by the
 -- appropriate power of two. Sum them up, and we should get an integer
@@ -27,7 +33,30 @@ octet_to_int x =
     8   * (bit_to_int (b5 x)) +
     4   * (bit_to_int (b6 x)) +
     2   * (bit_to_int (b7 x)) +
-    0   * (bit_to_int (b8 x))
+    1   * (bit_to_int (b8 x))
+
+
+
+octet_from_int :: Int -> Octet
+octet_from_int x
+    | (x < 0) || (x > 255) = Octet.None
+    | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
+    where
+      a1 = if (x > 128) then One else Zero
+      a2 = if ((x `mod` 128) >= 64) then One else Zero
+      a3 = if ((x `mod` 64)  >= 32) then One else Zero
+      a4 = if ((x `mod` 32)  >= 16) then One else Zero
+      a5 = if ((x `mod` 16)  >= 8)  then One else Zero
+      a6 = if ((x `mod` 8)   >= 4)  then One else Zero
+      a7 = if ((x `mod` 4)   >= 2)  then One else Zero
+      a8 = if ((x `mod` 2)   == 1)  then One else Zero
+
+
+octet_from_string :: String -> Octet
+octet_from_string s =
+    case (reads s :: [(Int, String)]) of
+      []   -> Octet.None
+      x:_ -> octet_from_int (fst x)
 
 
 -- The octet with the least possible value.