Re: What is f[1]? Advanced question
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- Subject: [mg131322] Re: What is f[1]? Advanced question
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Fri, 28 Jun 2013 04:13:33 -0400 (EDT)
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On 27/06/2013 11:25, amannucci wrote:
> Thanks. This is very helpful. I remain puzzled by this:
>
> u // FullForm
> FullForm[Symbol["u"]]
> FullForm[Unevaluated[Symbol["u"]]
> Head[u]
>
> FullForm[{1, 2, 3}]
> Head[{1, 2, 3}]
>
> In other words, Head and FullForm seem consist for the list, and inconsistent for the variable u. u's full form is just, literally "u", not Symbol["u"]. But the list's FullForm starts with "List". Head of Symbol["u"] is not Symbol, but "u". What gives?
>
>
I don't think there is too much mystery here - FullForm would simply be
too clumsy if it expanded symbols into Symbol constructs. As it is,
FullForm is incredibly useful.
I wish there was also a variant that did not evaluate its argument. True
one can write:
expression //Hold//FullForm
but the expression gets contaminated with Hold.
David Bailey
http://www.dbaileyconsultancy.co.uk
- References:
- What is f[1]? Advanced question
- From: amannucci <Anthony.J.Mannucci@jpl.nasa.gov>
- What is f[1]? Advanced question