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Re: What does FullForm[ ] actually do?

• To: mathgroup at smc.vnet.net
• Subject: [mg90572] Re: What does FullForm[ ] actually do?
• From: David Bailey <dave at Remove_Thisdbailey.co.uk>
• Date: Mon, 14 Jul 2008 05:20:50 -0400 (EDT)
• References: <g54oj0$eu9$1@smc.vnet.net> <g56t9n$3qv$1@smc.vnet.net> <g59tse$or2$1@smc.vnet.net>

AES wrote:

> 
> Thank you -- agreed --  that's what I've now learned from you and others 
> is how FF operates:  To say this (I think) more precisely: 
> 
>    "FullForm[expr] **first evaluates the expression expr** 
>     and then displays **the internal form of the _result_ 
>     produced by this evaluation of the expression**.
>  

I would not say this definition of FullForm is more precise at all. 
FullForm is exactly the same as Sin or Map - or the majority of other 
Mathematica functions - its arguments get evaluated before it is called. 
To define FullForm as above would imply that this is not the default 
behaviour of other Mathematica functions, and would logically require 
that these extra words be added to the definitions of all the non-held 
functions.

I often use FullForm[Hold[some expression]]

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