Function which returns all values associated with a symbol

Question

For example, I want a function that gives me all the values assigned to the one I give:

-> (giveme 'x '((x y) (x z) (b d) (x q)))

-> (y z q)

So the function should return in this case y z and q, as these are associated to x in pairs. Reason I ask this because I know there is a map function for it in one line.

`map` by itself won't do it, but `map` paired with `filter` will. — C. K. Young, Feb 03 '11 at 00:14

score 2 · Accepted Answer · answered Feb 03 '11 at 02:13

2

In Common Lisp:

CL-USER > (defun give-me (item list)
             (mapcan (lambda (e)
                       (and (eq item (first e)) (list (second e))))
                     list))
GIVE-ME

CL-USER > (give-me 'x '((x y) (x z) (b d) (x q)))
(Y Z Q)

answered Feb 03 '11 at 02:13

Rainer Joswig

136,269
10
221
346

score 1 · Answer 2 · answered Feb 04 '11 at 12:39

1

Common Lisp:

(defun giveme (key pairs)
  (loop for (k v) in pairs when (eq k key) collect v) )

Scheme:

(define (giveme key pairs)
  (apply append
    (map (lambda (p) (if (eq? key (car p)) (cdr p) '()))
      pairs )))

answered Feb 04 '11 at 12:39

WReach

18,098
3
49
93

score 0 · Answer 3 · answered Feb 03 '11 at 01:18

0

(define (giveme key dict)
        (map cadr 
          (filter 
            (lambda (x) (eq? key (car x)))
            dict
          )
        )
)

answered Feb 03 '11 at 01:18

philo

3,580
3
29
40

Function which returns all values associated with a symbol

3 Answers3