Re: How to evaluate parts of an expression, but not other parts?

*To*: mathgroup at smc.vnet.net*Subject*: [mg122703] Re: How to evaluate parts of an expression, but not other parts?*From*: Rui <rui.rojo at gmail.com>*Date*: Mon, 7 Nov 2011 05:51:07 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j930l9$a3d$1@smc.vnet.net>*Reply-to*: comp.soft-sys.math.mathematica at googlegroups.com

What about ReleaseHold[ Hold[(a + b) + (c + d)] /. i_Symbol /; Context[i] === "System`" :> Hold[i]] or maybe ReleaseHold[ Hold[(a + b) + (c + d)] /. i_Symbol /; Context[i] =!= "Global`" :> Hold[i]]