Issue #19

snippets/difference.md

@@ -1,13 +1,12 @@
 ### difference
 
-Returns the difference between two arrays.
+Returns the difference between two iterables.
 
-Create a `set` from `b`, then use list comprehension to only keep values not contained in `b`
+Use list comprehension to only keep values not contained in `b`
 
 ```python
 def difference(a, b):
-    b = set(b)
-    return [item for item in a if item not in b]
+    return [item for item in a if item not in b]
 ```
 ``` python
 difference([1, 2, 3], [1, 2, 4]) # [3]