Re: Converting a number back to a symbol?
- To: mathgroup at smc.vnet.net
- Subject: [mg82900] Re: Converting a number back to a symbol?
- From: Szabolcs Horvát <szhorvat at gmail.com>
- Date: Fri, 2 Nov 2007 05:04:48 -0500 (EST)
- References: <fgenct$fsd$1@smc.vnet.net>
AES wrote:
> If we have an expression containing integer powers of the symbol u0 and
> we know that u0's numerical value is (or at least eventually will be) u0
> = Pi/2, we know what happens if we write
>
> expr /. {u0 -> Pi/2}
>
> But what about the reverse case: we have an expression containing
> various integer powers of Pi, and we want to replace all the explicitly
> appearing Pi's by 2 u0. Writing
>
> expr /. {Pi-> 2 u0}
>
> doesn't seem to do it.
>
> Is there a way?
>
Can you give a full, evaluatable example?
It works for me:
In[1]:= Plus@@(Pi^Range[3])
Out[1]= Pi + Pi^2 + Pi^3
In[2]:= % /. Pi->2u0
Out[2]= 2 u0 + 4 u0^2 + 8 u0^3
--
Szabolcs