Re: Re: Help with output form?

*To*: mathgroup at smc.vnet.net*Subject*: [mg60953] Re: [mg60925] Re: [mg60902] Help with output form?*From*: Chris Chiasson <chris.chiasson at gmail.com>*Date*: Wed, 5 Oct 2005 02:27:53 -0400 (EDT)*References*: <200510030806.EAA00162@smc.vnet.net> <200510040524.BAA17881@smc.vnet.net>*Reply-to*: Chris Chiasson <chris.chiasson at gmail.com>*Sender*: owner-wri-mathgroup at wolfram.com

I used to try stuff like this. If you are careful, you could get away with the following: input[1]=lhs[1]==rhs[1] input[1]/.Equal->Set; However, you must then be careful to not use this trick with lhs[1] again, because it would be automatically evaluated. Following off of what Andrzej started, try: y=10 Rest[HoldForm@@First@Take[DownValues[In],{-2,-2}]] This second approach could even be extended to show all previous inputs. On 10/4/05, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote: > > On 3 Oct 2005, at 17:06, aufgang wrote: > > > I am struggling to get mathematica to output certain expressions the > > way I'd like and i'm wondering if anyone could help me. > > > > normally, when you input an expression using the Set operator (=), > > mathematica evaluates the expression, assigns the rhs to the lhs and > > returns the evaluated rhs (eg. y=Expand[(a+b)^2] -> a^2+2 a b +b^2) > > > > what I would like to do is coax mathematica to output the lhs as > > wel as > > the evaluated rhs (ie. y=Expand[(a+b)^2] -> y=a^2+2 a b +b^2). > > > > I want the rhs to be evaluated like normal, and the value of the > > lhs to > > be set to rhs, so so Hold, HoldForm, etc wont work (they keep the lhs > > but wont evaluate the rhs and the value isnt actually set) and I > > know I > > dont want to be using == instead of =. i just want the lhs to appear > > in the output. > > > > the reson I want to do this is because I am calling the Mathematica > > Kernel from a web app and I want to display this output format to the > > users. > > > > I suspect I could do this somehow by redefining Set or something but i > > can't seem to figure that out. > > > > Thanks for any help. > > > > > > > What you are asking for is strictly speaking impossible, since if y > has been assigned a^2+2 a b +b^2 as its value than whenever y is > evaluated it will be replaced by a^2+2 a b +b^2. There is no way to > do this without using some form of Hold. Probably the easiest > approach is: > > > y = Expand[(a + b)^2]; OwnValues[y][[1]] > > > HoldPattern[y] :> a^2 + 2*b*a + b^2 > > > If you do not want to see HoldPattern in your output you can replace > it by HoldForm: > > > y = Expand[(a + b)^2]; OwnValues[y][[1]] /. > {HoldPattern -> HoldForm} > > > HoldForm[y] :> a^2 + 2*b*a + b^2 > > In StandardForm or TraditionalForm you won't see the HoldForm. If you > still do not like :> you cannot simply replace it by = (Set) because > then Mathematica will attempt to set HoldForm[y] to the RHS (can't be > done without unprotecting HoldForm) and in any case the output again > would be just the RHS. If you really insist on having Set in your > output you have to wrap everything in HoldForm, e.g. > > > Block[{x}, y = Expand[(a + b)^2]; HoldForm[y -> x] /. {x -> y, Rule - > > Set}] > > HoldForm[y = a^2 + 2*b*a + b^2] > > > Andrzej Kozlowski > > -- Chris Chiasson http://chrischiasson.com/contact/chris_chiasson

**References**:**Help with output form?***From:*"aufgang" <aufgang@agile.net>

**Re: Help with output form?***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>