"UnFullForm"ing an Expression?

*To*: mathgroup at smc.vnet.net*Subject*: [mg13151] "UnFullForm"ing an Expression?*From*: siegman at ee.stanford.edu (AES)*Date*: Mon, 13 Jul 1998 07:42:03 -0400*Organization*: Stanford University*Sender*: owner-wri-mathgroup at wolfram.com

I recently posted a query noting that if you enter the following f1[a_,x_] :=a Cos[x] + a^2 Sin[x] f2[a_,x_] := D[f1[a,x],x] you can make a Table[ ] of f1[a,x] but not of f2[a,x]. If I look at the FullForms for these, e.g. f1[a,x] // FullForm f2[a,x] // FullForm they both look like simple functions to me (i.e., f2[a,x] shows no visible memory of having originated from a derivative), except the f2 is inside a "FullForm[ ]" wrapper and f1 isn't. Is there a way to "UnFillForm" f2 ? If so, would f2 from then on act like f1 ? Does this query make any sense? I'd like to understand the situation here. Thanks siegman at ee.stanford.edu