From: Carsten Eckelmann <careck@...42.com>
Date: 2004-01-13T09:18:54+09:00
Subject: Re: Getting the tail of a list?

Gennady wrote:

> Carsten Eckelmann wrote:
>
>> Hi everybody,
>>
>> I have spent the night reading about the wonders of Scheme at 
>> http://www.teach-scheme.org and have stumbled over a small demo program.
>>
>> This function checks whether a guest is on the guest list or not:
>>
>> (define (guest name list)
>>  (cond
>>    ((empty? list) 'no)
>>    ((equal? name (first list)) 'yes)
>>    (else (guest name (rest list)) )))
>>
>> I am in love with Ruby and I'm not about to switch to Scheme, so I 
>> wanted to write this in ruby:
>>
>> def guest (name, list)
>>  if list.empty?
>>    :no
>>  elseif name == list.first
>>    :yes
>>  else
>>    guest(name, list.rest)
>
>
> No Array#rest as you noted bellow, you may use list[1..-1] here. 

OKAY! That's a bit shorter, thanks.

>
> However, why not just this:
>
> def guest(name,list)
>   list.include?(name) ? :yes : :no
> end
>
> And what's wrong with boolean return values?

Yes of course that's the way to do it in ruby. My example was a bit of 
an academic exercise used to demonstrate recursive processing of lists 
to beginning students.
And there's nothing wrong with booleans, I just wanted to model the ruby 
code as close as possible to the scheme code.

Cheers,
Carsten.