Clojure Substitute Functions

Lookup

(defn lookup [i m]
  "This function looks up a value, i, in map m and returns the result if it exists, and otherwise returns i."
  (get m i i))

(defn lookup [i m]

"This function looks up a value, i, in map m and returns the result if it exists, and otherwise returns i."

(get m i i))

Note that (get m i i) can be abbreviated (m i i).

Usage example:

user=&gt; (lookup 'b '{a 1 b 2})
2
user=&gt; (lookup 'c '{a 1 b 2})
c

user=> (lookup 'b '{a 1 b 2})

user=> (lookup 'c '{a 1 b 2})

Substitute

(defn substitute [m l]
  (map (fn [i] (lookup i m)) l))

1 2	(defn substitute [m l] (map (fn [i] (lookup i m)) l))

Usage example:

user=&gt; (substitute '(a c b d) '{a 1, b 2})
(1 c 2 d)

1 2	user=> (substitute '(a c b d) '{a 1, b 2}) (1 c 2 d)

Note: There is a shortcut syntax for building lambda (anonymous) functions. Instead of (fn [i] …) write #( … ). If you have only one variable it is called %. If you have more than one they are %1, %2, … So this could be rewritten:

(defn substitute [l m]
  (map #(lookup % m) l))

1 2	(defn substitute [l m] (map #(lookup % m) l))

Deep Substitute

(defn deep-substitute [l m]
  (map (fn [i] 
         (if (seq? i)
           (deep-substitute i m)
           (lookup i m))) 
        l))

(defn deep-substitute [l m]

(map (fn [i]

(if (seq? i)

(deep-substitute i m)

(lookup i m)))

l))

Usage example:

user=&gt; (deep-substitute '(a (b a) (c) d) '{a 1, b 2})
(1 (2 1) (c) d)

1 2	user=> (deep-substitute '(a (b a) (c) d) '{a 1, b 2}) (1 (2 1) (c) d)

Hi There!

Lookup

Substitute

Deep Substitute