Re: What is f[1]? Advanced question

*To*: mathgroup at smc.vnet.net*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)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <20130626011408.DC7E86A2B@smc.vnet.net> <kqdshl$n34$1@smc.vnet.net> <kqh3u0$2im$1@smc.vnet.net>

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>