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Re: ParsedBoxWrapper's in packages

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115429] Re: ParsedBoxWrapper's in packages
  • From: Yaroslav Bulatov <yaroslavvb at gmail.com>
  • Date: Tue, 11 Jan 2011 00:32:36 -0500 (EST)

Wow, that looks complicated....is it likely to work in future versions?

At the core, I basically want
1. Have \[Element] work like MemberQ for lists.
2. Define functions that use f[a_\[Element] b_] syntax
3. Be able to import this functionality without breaking behavior or
functions like Reduce that use "Element" built-in

Is there perhaps a way to do this without Notation package?



On Mon, Jan 10, 2011 at 8:54 AM, Leonid Shifrin <lshifr at gmail.com> wrote:
> Hi Yaroslav,
>
> I could offer some chain of hacks, which, while not perfect, seem to do it.
>
> First, an example package:
>
> BeginPackage["NotationTest`"]
>
> mySum;
> myElement;
> plus;
>
> Begin["`Private`"];
>
> BeginPackage["Global`",{"Notation`","NotationTest`"}]
> InfixNotation[ParsedBoxWrapper["\[Element]"],myElement];
> EndPackage[]
>
> mySum[a_ \[Element] list_,expr_]:==plus[a,expr];
>
> End[]
> EndPackage[]
>
> Note that we wrap the calls to InfixNotation into BeginPackage and
> EndPackage in
> some special way. The next ingredient is a pretty dirty hack, for which I
> will probably be
> flamed:
>
> SetAttributes[loadWithNotations, HoldAll];
> loadWithNotations[code_] :==
>  Module[{oldSDdefs == DownValues[SetDelayed], temp, result},
>   Needs["Notation`"];
>   Unprotect[SetDelayed];
>   def : _SetDelayed /; (temp; True) :==
>    With[{dv == DownValues[SetDelayed]},
>     Unprotect[SetDelayed];
>     Clear[SetDelayed];
>     ReleaseHold@MakeExpression[MakeBoxes[def], StandardForm];
>     DownValues[SetDelayed] == dv;
>     Protect[SetDelayed]];
>   Protect[SetDelayed];
>   AbortProtect[Catch[Catch[result == code, _]]];
>   Unprotect[SetDelayed];
>   DownValues[SetDelayed] == oldSDdefs;
>   Protect[SetDelayed];
>   result]
>
> You must define this function in the Global` context before you load the
> packages. Now, assuming
> that you placed your package where Mathematica can find it (or appended its
> directory tp $Path),
> here is how you use it:
>
> loadWithNotations[
>  Needs["NotationTest`"];
> ]
>
> Let us now check the resulting definition:
>
> In[5]:== DownValues[mySum]//FullForm
>
> Out[5]//FullForm==
> List[RuleDelayed[HoldPattern[mySum[myElement[Pattern[NotationTest`Private`a,Blank[]],
> Pattern[NotationTest`Private`list,Blank[]]],Pattern[NotationTest`Private`expr,Blank[]]]],
> plus[NotationTest`Private`a,NotationTest`Private`expr]]]
>
> You can load several packages inside loadWithNotations. In each of these
> packages, you must isolate your
> calls to InfixNotation, as I did it here. Note that this will only work for
> definitions (with SetDelayed).
>
> Now, how does this work. It took me some time to figure this out. The
> problem is that Notation sticks to
> MakeBoxes/MakeExpression, which it redefines. But normally, when we read in
> packages (unlike when we enter expressions in interactive  FrontEnd
> sessions), they are parsed by some different means, so MakeExpression is not
> invoked. So, what I did here was to force the code to undergo
> MakeBoxes->MakeExpression transition during the time SetDelayed executes,
> thereby  forcing it to trigger the mechanisms of Notation. We need
> ReleaseHold because Notation`'s version of MakeBoxes wraps the result in
> HoldComplete, while we want it to execute. The reason why we need to wrap
> things in BeginPackage / EndPackage with Global` is that Notation` checks
> the $ContextPath for what is referred there as initializationContext
> variable, which must be on the $ContextPath.
>
> I can not say anything about the limitations of this approach, but it seems
> to work in simple cases. I haven't used
> Notation` package ever before, so it could be that I missed something
> important.
>
> Hope this helps.
>
> Regards,
> Leonid
>
> On Mon, Jan 10, 2011 at 10:39 AM, Yaroslav Bulatov <yaroslavvb at gmail.com>
> wrote:
>>
>> I'm trying to turn my notebooks into stand-alone packages and I'm
>> running into problems with Notation package. In particular, I'm using
>> Notation package and InfixNotation, and when I save notebook as a
>> package, I get "ParsedBoxWrapper"'s and definitions using infix
>> notation fail to match, for example.
>>
>> InfixNotation[ParsedBoxWrapper["\[Element]"], MyElement]
>> sum[a_ \[Element] list_, expr_] :== ...
>> sum[a_\[Element] {1,2,3},a]
>>
>> This fails to match when in .m file, but works fine in .nb file. My
>> question is -- how should I package "sum" so that it matches correctly
>> both in packages and in notebooks?
>>
>
>


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