Re: Subscript Bug?

*To*: mathgroup at smc.vnet.net*Subject*: [mg90124] Re: [mg90111] Subscript Bug?*From*: Carl Woll <carlw at wolfram.com>*Date*: Mon, 30 Jun 2008 04:51:25 -0400 (EDT)*References*: <200806290936.FAA29888@smc.vnet.net>

Aaron Fude wrote: >Hi, > >I have this code in a cell: > >Subscript[H, 1] = 110; Subscript[H, 2] = 90; >H = Subscript[H, 1] + Subscript[H, 2]; >Tanh[Subscript[H, 1]] > >The first time I execute the cell, I get > >Tanh[Subscript[200, 1]] > >which of course is nonsense. > > The first time you execute the cell, the assignment H = Subscript[H, 1] + Subscript[H, 2]; sets H to 110 + 90, which is 200. Then, Tanh[Subscript[200,1]] is what you get. The second time you execute the cell, H is 200, so Subscript[200,1] is set to 110 and Subscript[200,2] is set to 90. Then, H is set to 200 again. Now, Subscript[H,1] is Subscript[200,1] which equals 110, so you get Tanh[110]. If you want to do these kinds of manipulations with Subscript, then I recommend that you give Subscript the HoldFirst attribute. Carl Woll Wolfram Research >A second execution, yields the correct answer: > >Tanh[110] > >Is this a feature that I don't understand or a bug? > >

**References**:**Subscript Bug?***From:*Aaron Fude <aaronfude@gmail.com>