Re: Displaying a list of variables together with their names

*To*: mathgroup at smc.vnet.net*Subject*: [mg111195] Re: Displaying a list of variables together with their names*From*: Leonid Shifrin <lshifr at gmail.com>*Date*: Fri, 23 Jul 2010 07:12:00 -0400 (EDT)

Hi Szabolcs, > > > My Mathematica skills got a little rusty You are kidding, right? Seriously, I don't see an easy solution which would be much simpler conceptually - looks like some number of Unevaluated will be needed anyways in this approach. You can save some keystrokes by using Block trick though: ClearAll[dynamicVariableDisplayAlt]; SetAttributes[dynamicVariableDisplayAlt, HoldAll]; dynamicVariableDisplayAlt[vars__] := Dynamic@Grid[Block[{vars}, {SymbolName[#], #} & /@ {vars}], Alignment -> {{Left, "."}}]; Here I exploited the way name conflicts are resolved when RuleDelayed is the outer scoping construct - namely that it does not respect inner scoping constructs (Block here). So, while you get a warning by {vars} painted in red inside Block, it will work all right. You can also make this a pure function, which is a little more compact: dynamicVariableDisplayPure = Function[Null, Dynamic@Grid[Block[{##}, {SymbolName[#], #} & /@ {##}], Alignment -> {{Left, "."}}], HoldAll]; This example is actually quite interesting, since here, while Function is a lexical scoping construct, with slots is shows macro-like behavior. And I found very puzzling why this version with fixed number of named arguments also works: dynamicVariableDisplayPure3Args = Function[{x, y, z}, Dynamic@Grid[Block[{x, y, z}, {SymbolName[#], #} & /@ {x, y, z}], Alignment -> {{Left, "."}}], HoldAll]; For this, I have no explanation. I would expect Function to respect Block and therefore the names of the variables to be {"x","y","z"} and not {"a","b","c"}. But Function acted as ruthlessly as RuleDelayed here. Actually, the same can be seen on a much simpler example Function[x, Block[{x}, Print[x]]][1]. Regards, Leonid , I was wondering what > is a simpler / better way to achieve it than this: > > SetAttributes[dynamicVariableDisplay, HoldAll] > dynamicVariableDisplay[vars__] := > Dynamic@Grid[ > Transpose[{{Function[x, SymbolName[Unevaluated[x]], {HoldAll}] /@ > Unevaluated[vars]}, {vars}}], Alignment -> {{Left, "."}}] > > a=1; b=2; c=3; > > dynamicVariableDisplay[a, b, c] > > There's too much juggling with unevaluated symbols. > > Thanks for the help in advance, > Szabolcs > >