September Morn Update

Task/Huffman-coding/Haskell/huffman-coding-1.hs

@@ -1,6 +1,6 @@
-import Data.List
-import Control.Arrow
-import Data.Ord
+import Data.List (group, insertBy, sort, sortBy)
+import Control.Arrow ((&&&), second)
+import Data.Ord (comparing)
 
 data HTree a
   = Leaf a
@@ -10,7 +10,7 @@ data HTree a
 
 test :: String -> IO ()
 test =
-  mapM_ (\(a, b) -> putStrLn ('\'' : a : "\' : " ++ b)) .
+  mapM_ (\(a, b) -> putStrLn ('\'' : a : ("' : " ++ b))) .
   serialize . huffmanTree . freq
 
 serialize :: HTree a -> [(a, String)]
@@ -23,7 +23,7 @@ huffmanTree
   => [(w, a)] -> HTree a
 huffmanTree =
   snd .
-  head . until (null . tail) hstep . sortBy (comparing fst) . (second Leaf <$>)
+  head . until (null . tail) hstep . sortBy (comparing fst) . fmap (second Leaf)
 
 hstep
   :: (Ord a, Num a)
@@ -34,4 +34,7 @@ hstep ((w1, t1):(w2, t2):wts) =
 freq
   :: Ord a
   => [a] -> [(Int, a)]
-freq = ((length &&& head) <$>) . group . sort
+freq = fmap (length &&& head) . group . sort
+
+main :: IO ()
+main = test "this is an example for huffman encoding"

Task/Huffman-coding/Haskell/huffman-coding-2.hs

@@ -1,4 +1,3 @@
-*Main> test "this is an example for huffman encoding"
 'p' : 00000
 'r' : 00001
 'g' : 00010

Task/Huffman-coding/Julia/huffman-coding.julia

@@ -0,0 +1,53 @@
+abstract type HuffmanTree end
+
+struct HuffmanLeaf <: HuffmanTree
+    ch::Char
+    freq::Int
+end
+
+struct HuffmanNode <: HuffmanTree
+    freq::Int
+    left::HuffmanTree
+    right::HuffmanTree
+end
+
+function makefreqdict(s::String)
+    d = Dict{Char, Int}()
+    for c in s
+        if !haskey(d, c)
+            d[c] = 1
+        else
+            d[c] += 1
+        end
+    end
+    d
+end
+
+function huffmantree(ftable::Dict)
+    trees::Vector{HuffmanTree} = [HuffmanLeaf(ch, fq) for (ch, fq) in ftable]
+    while length(trees) > 1
+        sort!(trees, lt = (x, y) -> x.freq < y.freq, rev = true)
+        least = pop!(trees)
+        nextleast = pop!(trees)
+        push!(trees, HuffmanNode(least.freq + nextleast.freq, least, nextleast))
+    end
+    trees[1]
+end
+
+printencoding(lf::HuffmanLeaf, code) = println(lf.ch == ' ' ? "space" : lf.ch, "\t", lf.freq, "\t", code)
+
+function printencoding(nd::HuffmanNode, code)
+    code *= '0'
+    printencoding(nd.left, code)
+    code = code[1:end-1]
+
+    code *= '1'
+    printencoding(nd.right, code)
+    code = code[1:end-1]
+end
+
+const msg = "this is an example for huffman encoding"
+
+println("Char\tFreq\tHuffman code")
+
+printencoding(huffmantree(makefreqdict(msg)), "")