Selectors in Scheme R6RS

Question

I'm reading a old book

Simply Scheme: Introducing Computer Science

you can find it here .

In the fifth section it introduces the "selectors", operators like the following:

(first 'abcd) ;-> A
(butfirst 'abcd) ;-> BCD

and so on..

Does it exist something similar in R6RS? (since this operators are not defined).

You will need to port the Simply Scheme preamble which is not compatible with R6RS. I am not even sure it is possible as it uses 'funny' constructs. — leppie, Aug 18 '12 at 10:04
This question was asked before on SO. See [here](http://stackoverflow.com/questions/11593429/is-everything-a-list-in-scheme). If you want to learn standard Scheme, Simply Scheme is probably not the best book to read. — Asumu Takikawa, Aug 18 '12 at 16:52

score 3 · Accepted Answer · answered Aug 18 '12 at 10:08

As per my comment, this will probably be quite difficult.

Another aspect is that Simply Scheme sees symbols as 'strings'.

With that info you could write the following:

(define (first s)
  (string->symbol (string (car (string->list (symbol->string s))))))

(define (butfirst s)
  (string->symbol (apply string (cdr (string->list (symbol->string s))))))

Also note that symbols are case-sensitive in R6RS, so the result will be the same case case passed to the procedure.

Selectors in Scheme R6RS

1 Answers1