Access specific list parts in Racket/Scheme

Question

I am having trouble figuring out how to access specific pair information in Racket.

Say I am given some list like this:

(define database-of-components
'((p1 200 (2 p2) (3 p3))
(p2 8 (2 p4))
(p3 60 (1 p5) (2 p6) (3 p7))
(p4 2)
(p5 2)
...
))

How am I able to access the data contained in some individual pn? Say I am trying to get just 200 from p1 or just 60 from p3... how might I do this?

Note: This is obviously for a homework assignment but this question is just to get started.

uselpa · Accepted Answer · 2016-02-15 20:40:02Z

2

Look up assq and friends (assoc, assv):

> (assq 'p1 database-of-components)
'(p1 200 (2 p2) (3 p3))
> (second (assq 'p1 database-of-components))
200
> (second (assq 'p3 database-of-components))
60

answered Feb 15, 2016 at 20:40

uselpa

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