[Aldor-l] Collapse of function signatures

[Ralf Hemmecke]

Hello,

Look at the attached code foo.as.
There are two functions foo.
Unfortunately, their signatrues become indistinguishable for
Poly(MachineInteger). The compiler has no way to find out which foo(1) I
actually mean inside main(), so it takes the first one it finds. (Or can
I help the compiler somehow?)

In this little domain, it is easy to find out what will happen. But how
can one predict the result
- if one of the foo's is defined in another domain, or
- if only one foo is actually defined for Poly(R) and the other one is
added by an 'extend', or
- if foo appears in a category default?

In DistributedMultivariatePolynomial1(R, V, E) there are two functions
       *: (Integer, %) -> %
       *: (R, %) -> %
The first is implemented in sm_dmp1.as and the second in sm_dmp0.as.
Fortunately, they do not contradict.

Since the Aldor compiler still produces segfaulting code for 1*x (see
xxx.as), I wonder whether it gets confused for R=Integer by the
existence of one implementation in DistributedMultivariatePolynomial1
and the other in DistributedMultivariatePolynomial0. This guess is
supported by the code in xxx.as.

I agree that for efficiency reasons two * functions make sense, but I
would rather like that the semantic is made more explicit. For my foo.as
example, I would like that the more specific implementation is dominant.
So the output should always be [-1].

I know my wish is not easy to achieve, since one could have cases like
bar: (R, MachineInteger) -> %
bar: (MachineInteger, R) -> %
but no
bar: (MachineInteger, MachineInteger) -> %

Could the compiler at least warn if there is an _obvious_ collapse of
two function signatures, like with Integer or MachineInteger?

Ralf




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