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Re: The side-effects of mixing TraditionalForm inside expressions.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110802] Re: The side-effects of mixing TraditionalForm inside expressions.
  • From: AES <siegman at stanford.edu>
  • Date: Wed, 7 Jul 2010 07:42:29 -0400 (EDT)
  • References: <201007051002.GAA15102@smc.vnet.net> <i0urh5$6l9$1@smc.vnet.net>

In article <i0urh5$6l9$1 at smc.vnet.net>,
 Andrzej Kozlowski <akozlowski at gmail.com> wrote:

> 1 + Unevaluated[1]
> 
>  2

Fascinating.  I'd call this one more classic Mathematica gotcha, and one 
more example of fairly poor quality of Mathematica documentation -- or 
at least of the very arcane character of Mathematica for "ordinary 
users", once you get to any depth within it.

Help Browser says:

   Unevaluated[expr]
         represents the unevaluated form of expr when it appears as 
         the argument to a function. 

So, what does Unevaluated[expr] do when it is NOT the argument to a 
function?  

(The previous statement I'd say clearly implies that there are times 
when Unevaluated[expr] does appear as an arg to function, and therefore 
times when it does not -- and both need to be defined.)

So, if Unevaluated[expr] is entered all by itself in a cell, is it then 
"the argument to a function"?

If the cell contains 1 + Unevaluated[expr] as above, does that make the 
Unevaluated[expr] an argument to a function -- or not?  (I can see 
arguing that above queries either way -- and digging further down into 
the Help Browser examples is not very helpful.)

How would one find out from Mathematica documentation what "argument to 
a function" means, precisely?   Is there any significance to "argument 
to" rather than the (I think) more common usage "argument of"?

Is Unevaluated[expr] used in a syntactically acceptable way _always_ the 
argument to a function?


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