Re: Length of a held expression
- To: mathgroup at smc.vnet.net
- Subject: [mg96543] Re: Length of a held expression
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Mon, 16 Feb 2009 06:55:51 -0500 (EST)
- References: <gn8jdj$7qa$1@smc.vnet.net>
Nikolaus Rath wrote:
> Hello,
>
> How can I get the length of a list in a Hold[] expression? I.e. if
>
> b = Sequence[1,2];
>
> then I want the length of {b,3} given as 2. But
>
> Length[{b,3}]
>
> gives me the length after splicing in b (which is 4), while
>
> Length[Hold[{b,3}]]
>
> gives me the length of the hold expression (which is 1).
>
>
> Anyone able to help?
>
>
> Best,
>
> -Nikolaus
>
> --
> =C2=BBTime flies like an arrow, fruit flies like a Banana.=C2=AB
>
> PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C
>
I think it would help to describe what you are trying to do at a
slightly higher level, because Sequence does its thing even inside Hold
- for example:
Hold[Sequence[1, 2]]
David Bailey
http://www.dbaileyconsultancy.co.uk