Data commit

Task/LZW-compression/11l/lzw-compression.11l

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+F compress(uncompressed)
+   V dict_size = 256
+   V dictionary = Dict((0 .< dict_size).map(i -> (String(Char(code' i)), i)))
+   V w = ‘’
+   [Int] result
+   L(c) uncompressed
+      V wc = w‘’c
+      I wc C dictionary
+         w = wc
+      E
+         result.append(dictionary[w])
+         dictionary[wc] = dict_size
+         dict_size++
+         w = c
+
+   I !w.empty
+      result.append(dictionary[w])
+
+   R result
+
+F decompress([Int] &compressed)
+   V dict_size = 256
+   V dictionary = Dict((0 .< dict_size).map(i -> (i, String(Char(code' i)))))
+   V result = ‘’
+   V w = String(Char(code' compressed.pop(0)))
+   result ‘’= w
+   L(k) compressed
+      V entry = ‘’
+      I k C dictionary
+         entry = dictionary[k]
+      E I k == dict_size
+         entry = w‘’w[0]
+      E
+         exit(‘Bad compressed k: ’k)
+      result ‘’= entry
+      dictionary[dict_size] = w‘’entry[0]
+      dict_size++
+      w = entry
+
+   R result
+
+V compressed = compress(‘TOBEORNOTTOBEORTOBEORNOT’)
+print(compressed)
+print(decompress(&compressed))