Re: substitution within a substitution list
- To: mathgroup at smc.vnet.net
- Subject: [mg88590] Re: substitution within a substitution list
- From: Albert Retey <awnl at arcor.net>
- Date: Fri, 9 May 2008 03:25:01 -0400 (EDT)
- References: <fvudmu$ebg$1@smc.vnet.net>
Bipin wrote:
> HI,
>
> I'm trying to find a way of changing the substitution values within a
> substitution list.
>
> For example, if I have the following substitution list:-
>
> subs = {a->1, b->2, c->2}
>
> I want to programmatically replace the value associated with 'b' from
> 2 to 20, ie ending up with
>
> subs = {a->1, b->20, c->2}
>
> Does anyone know of a mathematica function for doing this?
yes :-). ReplaceAll, or /. for short:
subs /. (b -> _) -> (b -> 20)
depending on your expression and where they come from this might be more
robust:
Replace[subs, (Rule | RuleDelayed)[b, _] -> (b -> 20), {1}]
hth,
albert