June 2018 Update

Task/Run-length-encoding/Factor/run-length-encoding.factor

@@ -0,0 +1,18 @@
+USING: io kernel literals math.parser math.ranges sequences
+sequences.extras sequences.repeating splitting.extras
+splitting.monotonic strings ;
+IN: rosetta-code.run-length-encoding
+
+CONSTANT: alpha $[ CHAR: A CHAR: Z [a,b] >string ]
+
+: encode ( str -- str )
+    [ = ] monotonic-split [ [ length number>string ] [ first ]
+    bi suffix ] map concat ;
+
+: decode ( str -- str )
+    alpha split* [ odd-indices ] [ even-indices
+    [ string>number ] map ] bi [ repeat ] 2map concat ;
+
+"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
+"12W1B12W3B24W1B14W"
+[ encode ] [ decode ] bi* [ print ] bi@