Re: Sequence and Or
- To: mathgroup at smc.vnet.net
- Subject: [mg34197] Re: [mg34179] Sequence and Or
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Thu, 9 May 2002 05:15:59 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
On Wednesday, May 8, 2002, at 10:51 AM, DrBob wrote:
> Sorry. I don't misunderstand %, and that's not the problem, it's just
> that I stupidly added the second line manually to the text without
> evaluating it all again. I'll try again.
>
> {True,False,True}
> Or@@%
> Sequence@@%%
> Or[%]
> Or[Sequence@@{True,False,True}]
>
> evaluates to...
>
> {True,False,True}
> True
> Sequence[True,False,True]
> Sequence[True,False,True]
> Sequence[True,False,True]
>
> It's the last two outputs that mystify me, in which Sequence isn't
> evaluated when it needs to be.
OK, I see the mystery, it would make sense if Or had the HoldAllComplete
or SequenceHold attributes but it really only has the HoldAll attribute
which should allow Sequence objects to be threaded. It seems this is
just a problem with the documentation and HoldAll is the same as
HoldAllComplete with respect to Sequence. Wrapping the Sequence in an
Evaluate give the expected results. Is there no longer a difference
between HoldAll and HoldAllComplete in v4.1 or is this a bug?
Regards,
Ssezi