CoCoA » CoCoA-5

Here is a session sample:

>>> NewPolyRing(QQ, SymbolRange("x",2,1));
--> ERROR: Wrong number of indet names when creating a PPMonoid
--> [CoCoALib] NewPolyRing_DMPI pseudo ctor
--> NewPolyRing(QQ, SymbolRange("x",2,1));
--> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Currently SymbolRange returns an empty list, which evidently NewPolyRing does not like.
A KISS solution is simple to give a better error message when arg2 of NewPolyRing is empty.

My opinion:

What should SymbolRange do if there are no indets in the range?
empty list (non error)

What should NewPolyRing do if the result of SymbolRange is empty?
Give error

I'm cleaning up (right now) the input sanity checks for polynomial rings, they are quite messy and incoherent in the different implementations.

Now using ERR::Empty (maybe not ideal, but better)

/**/ NewPolyRing(QQ, "");
--> ERROR: Empty list or vector
--> [CoCoALib] NewPolyRing_DMPI pseudo ctor
--> NewPolyRing(QQ, "");
--> ^^^^^^^^^^^^^^^^^^^
/**/ NewPolyRing(QQ, []);
--> ERROR: Empty list or vector
--> [CoCoALib] NewPolyRing_DMPI pseudo ctor
--> NewPolyRing(QQ, []);
--> ^^^^^^^^^^^^^^^^^^^

Done and cvs-ed.
I cleaned up the code in the 3 files RingDistr.. and ediffed them so they are a little bit more similar (therefore, easier to maintain)