-- Shakespeare, Hamlet
The other day I found something interesting while reading Clojure Programming.
"While it might be counterintuitive, maps and vectors are both associative collections, where vectors associate values with indices."
-- Clojure Programming, page 100
This is yet another case of the book, Clojure Programming, stating something that I thought of but was unable to adequately express in words.
The differences placed around data structures are often either just in our minds or a condition you place on the structure its self.
In the case of the structures just being different in our minds we can look at the example of a map and vector in Clojure.
We see in the example above that we could use a vector as a map where the indices are the keys. We see in the first example (get v 1) that we are just using the index of 1 to get the second value from the vector (indices are zero based in Clojure). With the second example (get v 99 :not-found) we see that we can assign a default value to be return when a value is not found. In the last vector example we see that we can associate new values in the vector resulting in a different vector being returned (do not worry vectors are immutable in Clojure). In the map examples we see we can treat a map like a vector by using integers for the keys.
In the second case of data structures being different due to a condition imposed on them, we do not have to look an further than our example of a map.
We see a map is unordered in Clojure. If you want to have the data be stored in an order then you would want to use a sorted-map instead of a hash-map.
The differences placed around data structures are often either just in our minds or a condition you place on the structure its self.
In the case of the structures just being different in our minds we can look at the example of a map and vector in Clojure.
We see in the example above that we could use a vector as a map where the indices are the keys. We see in the first example (get v 1) that we are just using the index of 1 to get the second value from the vector (indices are zero based in Clojure). With the second example (get v 99 :not-found) we see that we can assign a default value to be return when a value is not found. In the last vector example we see that we can associate new values in the vector resulting in a different vector being returned (do not worry vectors are immutable in Clojure). In the map examples we see we can treat a map like a vector by using integers for the keys.
In the second case of data structures being different due to a condition imposed on them, we do not have to look an further than our example of a map.
(assoc m1 "Mr. Jack"0 20022 :good-boy);; {0 2002, 1 "Mr. Jack", 3 4, 2 :good-boy}
We see a map is unordered in Clojure. If you want to have the data be stored in an order then you would want to use a sorted-map instead of a hash-map.
