On Fri, Apr 02, 2021 at 02:45:02PM +0200, Ralf Hemmecke wrote:
> I have tried the following code.
>
> S ==> UnivariateLaurentSeries(Fraction Integer, 'x, 0)
> sx := x :: S
> s := (sx^3-7*sx)/(3*sx^7-sx^4)
> terms s
> TERMS n == [r for r in terms(s) while r.k < n]
> ll := TERMS 4
> entries ll
> entries TERMS 4
>
> Interestingly the last three evaluations show as:
>
> (6) -> ll := TERMS 4
> Compiling function TERMS with type PositiveInteger -> Stream(Record(
> k: Integer,c: Fraction(Integer)))
>
> (6)
> [[k = - 3, c = 7], [k = - 1, c = - 1], [k = 0, c = 21], [k = 2, c = - 3],
> [k = 3, c = 63]]
>
> Type: Stream(Record(k: Integer,c:
> Fraction(Integer)))
> (7) -> entries ll
>
> (7)
> [[k = - 3, c = 7], [k = - 1, c = - 1], [k = 0, c = 21], [k = 2, c = - 3],
> [k = 3, c = 63]]
>
> Type: List(Record(k: Integer,c:
> Fraction(Integer)))
> (8) -> entries TERMS 4
>
> >> Error detected within library code:
> infinite stream
>
> I am not afraid of the actual error, because in general that must be
> expected, but storing a value in a variable seems to make a difference
> for the interpreter. I'm not sure that an ordinary user likes or
> understands this.
>
> In fact, I don't understand why the "entries" function would get another
> argument value if called this or that way. What is happening here?
It is printing, not storing in variable. Compare:
ll := TERMS(4);
entries(ll)
entries(complete(TERMS(4)))
Printing have to compute few first terms of a stream. Entries
(and in general functions defined for finite aggreagates) works
only if all terms are already computed.
Also look at:
numberOfComputedEntries(TERMS(4))
explicitlyFinite?(TERMS(4))
numberOfComputedEntries(complete(TERMS(4)))
explicitlyFinite?(complete(TERMS(4)))
numberOfComputedEntries(ll)
explicitlyFinite?(ll)
--
Waldek Hebisch
--
You received this message because you are subscribed to the Google Groups
"FriCAS - computer algebra system" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/fricas-devel/20210402141347.GA4045%40math.uni.wroc.pl.
