[REBOL] Re: "piping" functions
From: volker::nitsch::gmail::com at: 24-Nov-2005 3:12
On 11/24/05, Jean-Francois Allie <jf_allie-hotmail.com> wrote:
>
> Graham,
>
> GC> "back tail series" returns the series one back from the end
>
> My understanding is that your statement isn't exactly correct since the
> wholeseries is in fact returned even if you only see it starting from the
> INDEX position.
>
Graham said "the series", not "a copy of the series". He could be more
verbose, "a reference to the series at the position one back from the
end", but it means the same.
> >>b: [1 2 3 4]
> == [1 2 3 4]
> >>c: back tail b
> == [4]
> >>head? c
> == false
> >>index? c
> == 4
> >>c: head c
> == [1 2 3 4]
> >>index? c
> == 1
>
> ... but if you do a copy then you do end up with a series that actualy
> startsat the INDEX.
>
> >>d: copy back tail b
> == [4]
> >>head? d
> == true
> >>index? d
> == 1
>
> This isn't to be nitpicking, but to understand these functions. Right now,
> with what I know, BACK TAIL B in this function:
>
> >>COPY/PART B BACK TAIL B
>
> doesn't return the same thing as in:
>
> >>BACK TAIL B
>
> why?
>
Hard to understand what you do not understand, i hope i do it:
The focus is here
copy/part B back tail b
not here:
copy/part b BACK TAIL B
copy B
return a copy of the series on position b.
copy/part B back tail b
returns a copy of the series on the position b, but not upto end, but upto
back tail b
>
> Gabriele,
>
> >>Actually, INDEX? is not needed.
>
> >>>>b: [1 2 3 4]
> >>== [1 2 3 4]
> >>>>copy/part b back tail b
> >>== [1 2 3]
>
> >>Regards,
> >>Gabriele.
>
> Yes precisely, but how come this function works without INDEX? as in
> Graham'sversion?
>
> cheers,
>
> JF
>
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--
-Volker
Any problem in computer science can be solved with another layer of
indirection. But that usually will create another problem.
David
Wheeler
