Results from trying to use "get" inside a Maxima function

Instead of

Test1(T):=block([temp,val,rank],temp:[T[val],T[rank]])$
  tensor[val]:matrix([1,2],[2,1]);
  tensor[rank]:'Trank2LL;
  Test1(tensor);

I would recommend:

Test1(T):=block([temp],temp:[T['val],T['rank]])$
  tensor['val]:matrix([1,2],[2,1]);
  tensor['rank]:'Trank2LL;
  Test1(tensor);

So that if val or rank are used as variables, there will be no conflict.

            -s

On Wed, Mar 9, 2011 at 17:19, Bruce Linnell <brlinnell at verizon.net> wrote:

>  I thought I'd pass along the results of everybody's suggestions, in case
> anything like this is ever needed or comes up again.
>
> My original goal was to attach a "quality" to a variable that has a value,
> so that when the variable was passed to a function, the function could take
> the appropriate steps based on the quality.  In particular, I'm trying to
> add to the CTensor package functionality, which requires knowing whether a
> tensor has upper and/or lower indices.  My goal is to be able to manipulate
> vectors, matrices, and arrays containing equations in order to multiply
> tensors, take the covariant derivative of them, raise/lower indices, etc.
>
> I would like to again thank everybody who replied to my original email,
> comments from *every* email I received were needed to be able to put all
> of the following together.
>
> Bruce
>
>
> Tests were done with XMaxima 5.23.2 in Windows XP.  The format is as
> follows :
>
> Method
> -----------
> Definition of the test function, to see if I can access both the value of
> the passed variable and its quality at the same time
>     Command-line statements used to set things up and call the test
> function
> Results
>
>
> get,put (quality passed attached to var)
> ----------------------------------------
> Test1(T):=block([temp],temp:[T,get(T,'Trank)])$
>   tensor:matrix([1,2],[2,1]);
>   put('tensor,'Trank2LL,'Trank);
>   Test1(tensor);
> Does not work : I tried all combinations of 'T and T in the function, and
> 'tensor and tensor in the function call.
>
>
> declare/feature (quality passed attached to var)
> ------------------------------------------------
> Test1(T):=block([temp],temp:[T,featurep('T,Trank2LL)])$
>   declare([Trank1U,Trank1L,Trank2UU,Trank2LL,Trank2UL,Trank2LU],feature);
>   tensor:matrix([1,2],[2,1]);
>   declare(tensor,Trank2LL);
>   Test1(tensor);
> Does not work : I tried all combinations of 'T and T in featurep.
>
>
> get,put (quality passed attached to var)
> ----------------------------------------
> Test1(T):=block([temp],temp:[ev(T),get(T,'Trank)])$
>   tensor:matrix([1,2],[2,1]);
>   put('tensor,'Trank2LL,'Trank);
>   Test1('tensor);
> This works, but you have to pass the variable as 'var in ALL function calls
>
>
> declare/feature (quality passed attached to var)
> ------------------------------------------------
> Test1(T):=block([temp],temp:[ev(T),featurep(T,Trank2LL)])$
>   declare([Trank1U,Trank1L,Trank2UU,Trank2LL,Trank2UL,Trank2LU],feature);
>   tensor:matrix([1,2],[2,1]);
>   declare(tensor,Trank2LL);
>   Test1('tensor);
> This works, but you have to pass the variable as 'var in ALL function calls
>
>
> quality passed explicitly
> -------------------------
> Test1(T,rank):=block([temp],temp:[T,rank])$
>   put('tensor,'Trank2LL,'Trank);
>   tensor:matrix([1,2],[2,1]);
>   Test1(tensor,get('tensor,'Trank));
> This works, but you have to include the get() in ALL function calls
> This almost always hangs after returning the result - I'm not sure why
> (just FYI, no reply needed)
>
>
> Create a structure with value+quality
> -------------------------------------
> Test1(T):=block([temp],temp:[T at val,T at rank])$
>   defstruct(Tensor(val,rank));
>   tensor:new(Tensor);
>   tensor at val:matrix([1,2],[2,1]);
>   tensor at rank:'Trank2LL;
>   Test1(tensor);
> This works!
>
>
> Hashed array containing value+quality
> -------------------------------------
> Test1(T):=block([temp,val,rank],temp:[T[val],T[rank]])$
>   tensor[val]:matrix([1,2],[2,1]);
>   tensor[rank]:'Trank2LL;
>   Test1(tensor);
> This works!
>
>
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