Re: How to call 'Clear' from within a function?
- To: mathgroup at smc.vnet.net
- Subject: [mg124884] Re: How to call 'Clear' from within a function?
- From: Yves Klett <yves.klett at googlemail.com>
- Date: Fri, 10 Feb 2012 05:58:10 -0500 (EST)
- Delivered-to: email@example.com
- References: <firstname.lastname@example.org>
This works just as expected if you simply use Clear[x]; instead of your ToString construct (which throws a warning anyway to tell you something is wrong). Regards, Yves Am 09.02.2012 11:40, schrieb James Stein: > Before trying to encapsulate 'Clear' in a function, I try this: > > Clear [ x ] ; > x > x = 2 > Clear [ ToString [ Unevaluated [ x ] ] ] ; > x > > And I expect to get three lines of output: x, 2, and x > But instead I get these three lines output: x, 2 and 2. > > What do I misunderstand, or need to know? > > I observe that a function CAN obtain the name of a symbol passed to it: > > ClearAll [ f ] ; > SetAttributes [ f, HoldFirst ] ; > f [ arg_ ] := ( Print [ Unevaluated [ arg ] ] ; > Clear [ ToString [ Unevaluated [ arg ] ] ] ) ; > x = 2; (* assign a value to 'x' *) > f [ x ] ; (* 'f' can print the symbol 'x' ! *) > x (* but 'x' still has value '2' ; the 'Clear' had no effect !? *) > > Similar problems with trying to call 'Set' from within a function....