On Mon, Oct 26, 2009 at 11:02 PM, Waldek Hebisch wrote:
>
>> Martin wrote:
>> >
>> > unparse((2*product(factorial i, i=0..n))::OUTFORM::INFORM)
>> >
>> > makes fricas crash...
>>
>
> The crash was due to spurious line that from the rewrite time.
> And it crashed on legal input too...
>
Thanks for finding the problem!
Bill Page wrote:
>> I guess it's no excuse for a break condition but I presume you
>> intended to write:
>>
>> (11) -> unparse((2*product(factorial i, i=0..n))::INFORM)
>>
>> (11) "2*%defprod(factorial(%A),%A,i,0,n)"
>> Type: String
> Another question is what we should generate for products,
> sums and integrals. The current result is _not_ valid as input...
>
Yes, that is an important point. Considering just product for the
moment, I took a quite look at the code in 'combfunc.spad.pamphlet'.
It seems that what one might like to produce as a general InputForm in
this case is
opdprod(factorial(%A),%A,i,0,n)
but 'opdprod' is not exported by 'CombinatorialFunction'. We do have
opdprod := operator('%defprod)$CommonOperators
evaluate(opdprod, iidprod)
iidprod l ==
(r1:=retractIfCan(fourth l)@Union(Z,"failed"))
case "failed" or
(r2:=retractIfCan(fourth rest l)@Union(Z,"failed"))
case "failed" or
(k:=retractIfCan(second l)@Union(K,"failed")) case "failed"
=> idprod l
*/[eval(first l,k::K,i::F) for i in r1::Z .. r2::Z]
and of course 'iidprod' is exported so we can write:
(5) -> iidprod([factorial(%A),%A,i,0,n])$CombinatorialFunction(INT,EXPR INT)
n
++-++
(5) | | i!
| |
i = 0
Type: Expression(Integer)
Really I suppose it would make sense to make the operators such as
'opdprod' available for this purpose and define
opdprod := operator('opdprod)$CommonOperators
But watch out for infinite loops here!
I was not able to locate any explicit code for coercion to InputForm.
Did I just miss it? If not I presume that the coercion is done via
OutputForm as Martin's original example may have implied:
setProperty(opdprod, SPECIALDISP, ddprod@(List F -> O) pretend None)
ddprod l ==
prod(summand(l)::O, third(l)::O = fourth(l)::O, fourth(rest l)::O)
Do you see any other way?
It seems that Martin re-wrote major parts of this pamphlet file. I
hope he has time to take a look at this.
Regards,
Bill Page.
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