June 2018 Update

Task/LZW-compression/BaCon/lzw-compression.bacon

@@ -0,0 +1,76 @@
+CONST lzw_data$ = "TOBEORNOTTOBEORTOBEORNOT"
+
+PRINT "LZWData: ", lzw_data$
+encoded$ = Encode_LZW$(lzw_data$)
+PRINT "Encoded: ", encoded$
+PRINT "Decoded: ", Decode_LZW$(encoded$)
+
+'----------------------------------------------------------
+
+FUNCTION Encode_LZW$(sample$)
+
+    LOCAL dict ASSOC int
+    LOCAL ch$, buf$, result$
+    LOCAL nr, x
+
+    FOR nr = 0 TO 255
+        dict(CHR$(nr)) = nr
+    NEXT
+
+    FOR x = 1 TO LEN(sample$)
+
+        ch$ = MID$(sample$, x, 1)
+
+        IF dict(buf$ & ch$) THEN
+            buf$ = buf$ & ch$
+        ELSE
+            result$ = APPEND$(result$, 0, STR$(dict(buf$)))
+            dict(buf$ & ch$) = nr
+            INCR nr
+            buf$ = ch$
+        END IF
+    NEXT
+
+    result$ = APPEND$(result$, 0, STR$(dict(buf$)))
+
+    RETURN result$
+
+END FUNCTION
+
+'----------------------------------------------------------
+
+FUNCTION Decode_LZW$(sample$)
+
+    LOCAL list$ ASSOC STRING
+    LOCAL old$, ch$, x$, out$, result$
+    LOCAL nr
+
+    FOR nr = 0 TO 255
+        list$(STR$(nr)) = CHR$(nr)
+    NEXT
+
+    old$ = TOKEN$(sample$, 1)
+
+    ch$ = list$(old$)
+    result$ = ch$
+
+    FOR x$ IN LAST$(sample$, 1)
+
+        IF NOT(LEN(list$(x$))) THEN
+            out$ = list$(old$)
+            out$ = out$ & ch$
+        ELSE
+            out$ = list$(x$)
+        END IF
+
+        result$ = result$ & out$
+        ch$ = LEFT$(out$, 1)
+        list$(STR$(nr)) = list$(old$) & ch$
+
+        INCR nr
+        old$ = x$
+    NEXT
+
+    RETURN result$
+
+END FUNCTION