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Re: UpValues for expressions headed by a string

• To: mathgroup at smc.vnet.net
• Subject: [mg63086] Re: UpValues for expressions headed by a string
• From: dh <dh at metrohm.ch>
• Date: Tue, 13 Dec 2005 03:41:46 -0500 (EST)
• References: <dn8fra$bof$1@smc.vnet.net> <dn8r0m$hl5$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi Trevor,
according to our private conversation you have problems implementing a 
function that takes different types in different packages.

Well, a symbol can only live in one context. Therefore, if you define 
the behaviour of a symbol in more than one package, you must take care 
to give the right context:
- The first package will set the context. The usage message must go here.
- all further packeges must address the symbol with the right context. 
No usage statement here.

Here is an example:

BeginPackage["aa`"];
fun::usage = "blabla";
Begin["Private`"]
fun[x_Integer] := Print[x];
End[]
EndPackage[]

BeginPackage["bb`"];
Begin["Private`"]
aa`fun[x_String] := Print[x];
End[]
EndPackage[]

Note the aa` in the second package.

Daniel