On Sat, Mar 03, 2012 at 09:48:36PM +0100, Ralf Hemmecke wrote:
> Hi Sergei,
>
> On 03/03/2012 10:32 AM, Serge D. Mechveliani wrote:
>> And I am going to build constructions like this:
>>
>> constr := UPConstr(x, FrCons("Int" :: Symbol))
>>
>> And to analyse it like this
>>
>> f(constr) ==
>> constr case of Fr =>
>> constr' := frConstrArg constr
>> process the argument construction constr'
>> constr case of UP' =>
>> x := upConstrVar constr
>> cConstr := upConstrCoef constr
>> process x and the coefficient domain construction cConstr
>>
>> This approach looks rather complex, and even requires to introduce a
>> category.
>> I thought of SExpression. But, for example,
>> convert[UP', x, coefConstr'] :: SExpressin
>>
>> requires of UP', x, constr' to be of the same type. Right?
>> One neds to union the constructor tags, parameters (like x),
>> and domain constructions into a certain type U, and to program
>> processing the data in List U ...
>
> Can you be a bit more precise? All I see is some code that looks like
> Haskell and would certainly not be the way it would be programmed in
> SPAD. It would be helpful, if you state, what you actually want to
> achieve. From what I've read in your mail, all I can say is that you
> want something like Any, but not encoding every type. In other words, I
> think that you want tagged unions, but I'm not quite sure.
>
> However, if you want something like Any or tagged union, then it looks
> like you basically want to throw away the type information. I'm sure
> there is some better way to achieve your goal in SPAD, but what is your
> goal?
>
The question can be reformulated: what Spad has for the tagged union?.
The initial goal is explained in the first my letter on this subject.
I repeat:
to define a type DomConstr
for an explicit symbolic representation of a domain construction
-- for a domain built by any correct composition of
INT, Fraction, UP, POLY, ResidueRingOfEuclideanRing.
(let it be this small set, so far)
-- each of these constructors has its individual tuple of argument types.
It must be so that a Spad program
could process constr : DomConstr as a first-class data, in particular,
to extract each part of constr : DomConstr.
For example, if constr : DomConstr represents the domain
UP(x, Fraction INT),
then, it is possible to extract from it the
tag "UP", variable x, (construction of Fraction INT) : DomConstr,
tag "Fraction", (construction of INT) : DomConstr.
I do not think that this needs `Any'.
In Haskell, it is done by a tagged union.
In Spad, I do not find tagged union.
(1) I tried to define domains and type union, as in my first letter.
(2) I thought of SExpression.
(3) In my second letter I applied Records.
Records do work for this goal, but they do not so precisely fit this goal.
For example, is it possible to define DomConstr as a
tagged union of several records?
Thanks,
------
Sergei
[email protected]
--
You received this message because you are subscribed to the Google Groups
"FriCAS - computer algebra system" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/fricas-devel?hl=en.
