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Re: Converting a number back to a symbol?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82966] Re: Converting a number back to a symbol?
  • From: AES <siegman at stanford.edu>
  • Date: Mon, 5 Nov 2007 05:01:33 -0500 (EST)
  • Organization: Stanford University
  • References: <fgenct$fsd$1@smc.vnet.net>

In article <fgenct$fsd$1 at smc.vnet.net>, AES <siegman at stanford.edu> 
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 . . . 

My abject apologies for this -- utter stupidity in action.

My test case was (in separate cells):

      u0 =  Pi/2;

      f = u0 + 2 u0^2 + 4 u0^2

      f /. {Pi -> 2 u0}


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