Mathematica 10 has introduced Associations, elsewhere known as hash tables or dictionaries. Is there Ordered equivalent like in Python, Java, .NET? The data structure should remember the order in which key-value is inserted.
That associations are ordered can be easily demonstrated.
assoc = <|a -> x, b -> y, c -> z|>; assoc[d] = 42; assoc
<|a -> x, b -> y, c -> z, d -> 42|>
assoc[a] = w; assoc
<|a -> w, b -> y, c -> z, d -> 42|>
Since the key
d did not exist, the key, value pair
d -> 42 was added to the end of the association. On the hand since the key
a did exist, it's position was preserved.