Re: substitution within a substitution list

*To*: mathgroup at smc.vnet.net*Subject*: [mg88592] Re: substitution within a substitution list*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Fri, 9 May 2008 03:25:24 -0400 (EDT)

On 5/8/08 at 4:13 AM, bipin.caz at googlemail.com (Bipin) wrote: >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? Sure. Use a replacement rule with HoldPattern. For example, In[4]:= subs /. HoldPattern[a_ -> _] -> a -> 20 Out[4]= {a->20,b->20,c->20}