I have a replacement rules list, but its quite long and therefore I would like to make a standalone package of it. I tried but haven't succeeded. A simple example of my approach is
BeginPackage["Rules`"]
Rules::usage="Rules[x] applies rules on expression x."
Begin["Private`"]
RulesDef = {a->2,b->3};
Rules[expr_]:=expr//.RulesDef
End[]
EndPackage[]
However, when I call Rules[a + b], it gives me a + b instead of 5.
How should I put such a rules into a package, if it is possible?
Because you want your rules to be evaluated in the same context as the expression you are applying them to, I don't think a real package is what you want. I think saving your rule definition in a package (.m) file without the package trimmings -- which create a new context -- will work for you.
Make a new notebook with just one cell containing
myRules = {a -> 2, b -> 3};
Make the cell a initialization cell.
Save the notebook to FileNameJoin[{$UserBaseDirectory, "Applications"}] as myRules.m.
Now in any note book you can write
<< "myRules.m"
a + b /. myRules
5
As an alternative, if you have V10.2 or later, you could make myRules a LocalSymbol.
myRules immediately after loading myRules.m with << -- you should see {a -> 2, b -> 3}. As to your second issue, you could put myRules = {a -> 2, b -> 3}; in an initialization cell at beginning of your package file (before BeginPackage[]).
$\endgroup$
Commented
Mar 12, 2016 at 17:19
I think using the usual package syntax is fine. You just need to add the Symbol RulesDef to the global context. Thus your package could look like this:
BeginPackage["Rules`"]
RulesDef::usage="Boo"
Rules::usage="Rules[x] applies rules on expression x."
Begin["Private`"]
RulesDef = {Global`a->2,Global`b->3};
Rules[expr_]:=expr//.RulesDef
End[]
EndPackage[]
Its necessary to addd Global` infront of the variables cause otherwise their context will be private.
