Dirty trick or legitimate style?

*To*: mathgroup at smc.vnet.net*Subject*: [mg4036] Dirty trick or legitimate style?*From*: hagai at helix.nih.gov (Hagai Agmon-Snir)*Date*: Tue, 28 May 1996 01:45:51 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hi, Mathematica experts, I am improving a package that I wrote a while ago. One of the things I wanted to add is a function that gets an "operator" (practically, a Mathematica expression), and performs this operation on the internal tree structure (that is a part of the Private context of the package). I pass the operator as a string and use ToExpression to calculate it in the function (any better ideas?). Problem: the operator will not be calculated in the correct "Private" context. I solve this problem by the following "dirty" trick, that seems to work fine - but ignores the style of Mathematica programming (I think). I enclose just a tiny portion of the package - but the definition of EvaluateCommand demonstrate the trick and GeneralTransform shows an example of actual use. I am far from being a Mathematica expert, not speaking of package-writing. If you have any better idea or if you think it is OK with the "Mathematica code of style" - please let me know. You might also see "real" problems with this trick (that are worse than the stylistic one). BeginPackage["MET`", {"Graphics`Legend`","Graphics`Colors`"}]; EvaluateCommand::usage = " "; GeneralTransform::usage = " "; Begin["`Private`"]; EvaluateCommand[stringarg_]:=Module[{tmp},( BeginPackage["MET`", {"Graphics`Legend`","Graphics`Colors`"}]; Begin["`Private`"]; tmp=ToExpression[stringarg]; End[]; EndPackage[]; tmp )] GeneralTransform[lroot_,stringarg_]:= Module[{tmp},( BeginPackage["MET`", {"Graphics`Legend`","Graphics`Colors`"}]; Begin["`Private`"]; tmp=ToExpression[stringarg]; tmp=Evaluate[tmp]&; PassTreeRecursive[lroot, ((#[Strl]=(N[tmp[#]]))&) ]; End[]; EndPackage[]; )]; PassTreeRecursive[lroot_,lfunc_] := ( Apply[lfunc,List[lroot]]; If[Length[lroot[Schildren]] >0 , Map[PassTreeRecursive[#,lfunc]&,lroot[Schildren]]]; ); End[]; EndPackage[]; Yours, Hagai Agmon-Snir >>>>>>>>>>>>>>>>>> ================================ <<<<<<<<<<<<<<<<< Hagai Agmon-Snir Tel: (301) 496-9972 (301) 496-4325 Surface mail: Fax: (301) 402-0535 Mathematical Research Branch, NIDDK 9190 Rockville Pike - Suite 350 Bethesda, MD 20814-3800 USA E-mail: hagai at helix.nih.gov WWW: http://mrb.niddk.nih.gov/hagai <<<<<<<<<<<<<<<<< ================================ >>>>>>>>>>>>>>>>>> ==== [MESSAGE SEPARATOR] ====