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Background: Every application has user-definable constants. The Java language has the Properties class to handle them.

Question: What is a good and re-usable coding style for setting and changing application level constants in Mathematica?

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  • $\begingroup$ Would you describe in further detail what you need? I am not familiar with Java so your analogy does not help me. $\endgroup$
    – Mr.Wizard
    Commented Jun 19, 2012 at 18:03
  • $\begingroup$ Think of values like directories, authorization, connection strings for a database, ip addresses, logging level etc. Things that are relatively constant for several apps, but may need to be changed in an easy way. - It's easy to do but I would like to know how you guys do it and what standards you use, in Java for example it is common to name constants in ALLUPPERCASE. $\endgroup$
    – nilo de roock
    Commented Jun 19, 2012 at 18:47
  • $\begingroup$ What kind of interface does your application have? Notebook? Java? $\endgroup$
    – Mr.Wizard
    Commented Jun 19, 2012 at 18:48
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    $\begingroup$ Since it seems like you want constants accessible from a number of applications, why not create a package of constants and start each application by calling the constants you need. You would then change the constants only in the package should they ever need changing. $\endgroup$
    – Jagra
    Commented Jun 19, 2012 at 19:00
  • $\begingroup$ @Mr.Wizard - The user-interface is ( currently ) Notebook, and Java is used for custom language parsing ( ANTLR ). $\endgroup$
    – nilo de roock
    Commented Jun 19, 2012 at 19:21

1 Answer 1

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Since it seems like you want constants accessible from a number of applications, why not create a package of constants and start each application by calling the constants you need. You would then change the constants only in the package should they ever need changing.

    (* Mathematica Package *)

    BeginPackage["CONSTANTS`"]
    (* Exported symbols added here with SymbolName::usage *)  

    constant1::usage = "some text"
    constant2::usage = "some text"
    constant3::usage = "some text"

    Begin["`Private`"] (* Begin Private Context *) 

    constant1[]: = 22;
    constant2[]: = "myConstant";
    constant3[]: = 0.618;

    End[] (* End Private Context *)

    EndPackage[]

See: Package development Place package in an appropriate directory so Mathematica can see it.

To give your notebooks access to the constants:

Needs["CONSTANTS`"]

constant1[]
constant2[]
constant3[]

22
"myConstant"
0.618

Just a sketch but this should give you the idea.

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  • $\begingroup$ Mathematically elegant. "For constants define a function that returns a constant." $\endgroup$
    – nilo de roock
    Commented Jun 20, 2012 at 8:25
  • $\begingroup$ Thank for noticing ;-) It did occur to me that Mathematica looks at everything as an expression. Some OOP languages also see variables and constants as objects. $\endgroup$
    – Jagra
    Commented Jun 20, 2012 at 13:42

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