Skip to main content

Same name for functions in package and Global context


I am using a package that was written for Mathematica 3 while I am now working on Mathematica 8. I have issues with 2 functions in particular, Order and GraphComplement. They are a part of this package but are also present in Mathematica 8 by default but with distinctly different arguments and working. (I am assuming they weren't around in Mathematica 3)


Now when I make use of some other functions in this package they make calls to both Order and GraphComplement and it keeps trying to use the in built wolfram version. I instead want it to use the one that comes with the package.


Can anyone point me to the right direction?



Answer



If I understand the problem I think I can help, but what I propose is a bit weird. I think you have a package that uses the unqualified Symbol name Order internally, and you need the package not to see the System`Order Symbol while it is defined. To effect this you can temporarily change the Context of Order, then put it back after loading the package.



As an example here is a bare-bones package defining a function foo that uses an internal definition for Order:


BeginPackage["MyStuff`"]

foo::usage = "my function";

Begin["`Private`"]

Order[args___] := {args} === Sort[{args}];

foo[a_, b_] := If[Order[a, b], "Arguments are in order", "Arguments are out of order"]


End[]

EndPackage[]

After saving this to foo.m if I call Get[foo.m] and try to use foo I have a problem:


Get["foo.m"]

foo[1, 2]



SetDelayed::write: Tag Order in Order[args___] is Protected. >>


If[1, "Arguments are in order", "Arguments are out of order"]

But if, after restarting the kernel, I first move Order out of the System context before loading the package:


Context[System`Order] = "hold`";

Get["foo.m"]

Context[hold`Order] = "System`";


I can now call my foo as intended:


foo[1, 2]
foo[4, 2]


"Arguments are in order"

"Arguments are out of order"


This works because while the package is being defined Order is not found in the context path, and a new Symbol MyStuff`Private`Order is created and defined instead:


Definition[foo]


foo[MyStuff`Private`a_, MyStuff`Private`b_] := 
 If[MyStuff`Private`Order[MyStuff`Private`a, MyStuff`Private`b],
   "Arguments are in order",
   "Arguments are out of order"]

And Order still works elsewhere as its context is restored:



Order["a", "b"]


1

Comments

Post a Comment

Popular posts from this blog

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...
Post a Comment
Read more

mathematical optimization - Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. vars = u@# & /@ Range[3]; cons = Flatten@ { Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; Minimize[{Total@((vec1[[#]] - vec2[[u[#]]])^2 & /@ Range[1, 3]), cons}, vars, Integers] The error I get: Part::pkspec1: The expression u[1] cannot be used as a part specification. >> Answer Ok, it seems that one can get around Mathematica trying to evaluate vec2[[u[1]]] too early by using the function Indexed[vec2,u[1]] . The working MWE would then look like the following: vars = u@# & /@ Range[3]; cons = Flatten@{ Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; NMinimize[ {Total@((vec1[[#]] - Indexed[vec2, u[#]])^2 & /@ R...
Post a Comment
Read more

plotting - Plot 4D data with color as 4th dimension

I have a list of 4D data (x position, y position, amplitude, wavelength). I want to plot x, y, and amplitude on a 3D plot and have the color of the points correspond to the wavelength. I have seen many examples using functions to define color but my wavelength cannot be expressed by an analytic function. Is there a simple way to do this? Answer Here a another possible way to visualize 4D data: data = Flatten[Table[{x, y, x^2 + y^2, Sin[x - y]}, {x, -Pi, Pi,Pi/10}, {y,-Pi,Pi, Pi/10}], 1]; You can use the function Point along with VertexColors . Now the points are places using the first three elements and the color is determined by the fourth. In this case I used Hue, but you can use whatever you prefer. Graphics3D[ Point[data[[All, 1 ;; 3]], VertexColors -> Hue /@ data[[All, 4]]], Axes -> True, BoxRatios -> {1, 1, 1/GoldenRatio}]
Post a Comment
Read more