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Re: 2.9.2 How Input and Output Work

• To: mathgroup at smc.vnet.net
• Subject: [mg61878] Re: 2.9.2 How Input and Output Work
• From: David Bailey <dave at Remove_Thisdbailey.co.uk>
• Date: Thu, 3 Nov 2005 04:58:47 -0500 (EST)
• References: <dk6v53$fh2$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Steven T. Hatton wrote:
> 2.9.2 How Input and Output Work of the online help states that:
> 
> "When you type something like x^2 what Mathematica at first sees is just the
> string of characters x, ^, 2. But with the usual way that Mathematica is
> set up, it immediately knows to convert this string of characters into the
> expression Power[x, 2]."
> 
> What does "immediately" mean in this context?  As soon as I press the '2'
> key?  When I evaluate the cell?  If it is the former, then why do I see
> "Cell[BoxData[SuperscriptBox["x", "2"]], "Input"]" when I view the
> expression?
Hello,

If you are seeing a SuperScriptBox, then you either input your x^2 using 
a palete/Ctrl^/etc - so there wasn't just a string of normal characters 
- or perhaps you converted the input to StandardForm after typing it in. 
There are two distinct things going on here - conversion to a 
SuperScriptBox - which is done by the FrontEnd, and the subsequent 
conversion of x^2 or the corresponding BoxForm expression to Power[x,2] 
- which is done by the kernel when you actually execute the cell. Note 
that the kernel understands both the linear list of characters OR the 
BoxForm expression.

David Bailey
http://www.dbaileyconsultancy.co.uk