Re: ReplaceAll question
- To: mathgroup at smc.vnet.net
- Subject: [mg82562] Re: ReplaceAll question
- From: Albert <awnl at arcor.net>
- Date: Wed, 24 Oct 2007 04:37:02 -0400 (EDT)
- References: <ffkf46$sh6$1@smc.vnet.net>
Yaroslav Bulatov wrote:
> b = 3;
> Hold[a[[b]]] /. {b -> c}
>
> ReplaceAll has no effect, why?
Because the rule b -> c is evaluated to 3 -> c
before it is applied, and the latter doesn't
match anything, which at least is better than
to match something that shouldn't...
> What is the recommended way of carrying
> out the replacement above?
Hold[a[[b]]] /. {HoldPattern[b] -> c}
hth,
albert