Try
GETDATABASE('AbelianMonoid, 'CONSTRUCTORCATEGORY)$Lisp and
GETDATABASE('DistributionCategory, 'CONSTRUCTORCATEGORY)$Lisp
While in the first case we have in the returns expression
(SIGNATURE (Zero) ($) constant)
the second call yields
(SIGNATURE (Zero) ($))
without the "constant" marker.
AbelianMonoid defines
0 : constant -> %
while DistributionCategory defines
0 : () -> %
I consider "constant -> %" as a funny writing for "%", the mapping
() -> % is clearly not the same type as %. Mathematically, yes, there's
no difference, but ()->% can have side effects in SPAD, while % can not.
It probably currently makes no difference in FriCAS, but I would rather
like to write
0: %
into the .spad file instead of "constant -> %" or "() -> %".
Furthermore since the type ()->% is for me not equivalent to %, I
consider it even a bug.
Distribution(R) implements 0 via
0 == distributionByMoments sequence repeating [0]
but we have
distributionByMoments : Sequence R -> %
so the result type is clearly % and not ()->%.
Waldek, can we get rid of "constant->" and "()->" for the definition of
constants already now? I think you've worked on this, but I'm not sure
about the status.
Ralf
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