tasks a-s

Task/Permutations/CoffeeScript/permutations-1.coffeescript

@@ -0,0 +1,18 @@
+# Returns a copy of an array with the element at a specific position
+# removed from it.
+arrayExcept = (arr, idx) ->
+	res = arr[0..]
+	res.splice idx, 1
+	res
+
+# The actual function which returns the permutations of an array-like
+# object (or a proper array).
+permute = (arr) ->
+	arr = Array::slice.call arr, 0
+	return [[]] if arr.length == 0
+	
+	permutations = (for value,idx in arr
+		[value].concat perm for perm in permute arrayExcept arr, idx)
+	
+	# Flatten the array before returning it.
+	[].concat permutations...

Task/Permutations/CoffeeScript/permutations-2.coffeescript

@@ -0,0 +1,7 @@
+coffee> console.log (permute "123").join "\n"
+1,2,3
+1,3,2
+2,1,3
+2,3,1
+3,1,2
+3,2,1