Re: Hints on recursion


Geoffrey Summerhayes ha scritto:

> Prolog [Head | Tail], [A, B | Tail]
> Lisp (car . cdr), (first second . rest)
>
> A list, e.g. '(1 2 3), is essentially shorthand for the dotted
> equivalent,
> in this case: '(1 . (2 . (3 . nil)))
>

Yes, I knew this, but...

> So if we substitute a list, for example '(g h i), for rest into
> Pascal's
>
> (twice 'e '(e . rest)) = (once 'e . rest)
>
> we get
>
> (twice 'e '(e g h i)) = (once 'e '(g h i))

in my opinion if you substitute '(g h i) to rest you'll get:

(twice 'e '(e quote (g h i))) = (once 'e quote (g h i))

or:

(twice 'e '(e g h i)) = (once 'e g h i)

Am I wrong?

I first thought to a shorthand to apply:

(let ((rest-list '(1 2 3)))
(apply #'+ rest-list)

or simply:

(+ . rest-list))

but in Scheme it doesn't work.

I don't know if in CL it works or not, so I asked what that point
was...

matteo

>
> See http://www.lispworks.com/documentation/HyperSpec/Body/02_da.htm
>
> --
> Geoff

.

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