CoCoA » CoCoALib

Many errors now are called Not... (e.g. NotNonZero) but that's ambiguous/confusing.
Suggestion: rename them Need... (e.g. NeedNonZero)

Joke: does that mean that NotYetImplemented should become NeedImplementing? ;-)

Anna Maria Bigatti wrote:

Many errors now are called Not... (e.g. NotNonZero) but that's ambiguous/confusing.
Suggestion: rename them Need... (e.g. NeedNonZero)

I'm quite keen to change the names (I'm confused myself in the meaning of the negation)
NeedNonZero or MustBeNonZero?

In the error messages there are some "is not" and some "must be"

    DEFINE_ERROR(NotPositive, "Value is not positive");
    DEFINE_ERROR(NotPositiveGrading, "Grading must be positive");

My current thoughts abou the design of errors is that CoCoALib errors will be represented as instances of very few distinct classes -- right now, I am thinking of just a single class (see #385).

If my current ideas come to fruition then essentially all details about the error will have to be in the string, but I would like the strings for different messages to be fairly uniform e.g. where appropriate we always write must be positive, rather than using other variants with much the same meaning (such as should be positive, expected positive, and so on).

• out of range
• must be positive
• must be non-negative

They do all convey the idea of being "out of range", but I think it may be kinder to the user to have a "positive"/"non-negative" message -- because those messages give an indication about which range is valid!

I simplified a few error messages and clarified error for PolyRingHom. Excerpt (

    const std::string FnName = "PolyRingHom(Rx,S,CoeffHom,IndetImages)";
    (...)
    if (codomain(CoeffHom) != S)
      CoCoA_ERROR(ERR::BadCodomain, FnName + ": argument CoeffHom");
    if (NumIndets(Rx) != len(IndetImages))
      CoCoA_ERROR(ERR::BadArraySize, FnName + ": arguments Rx, IndetImages");

I'm not changing the names now (good names are for developers, good messages are for the users! ... and the developers ;-). Anyway BadArraySize should be IncompArraySize.

.... just to explain what I'm doing and why: I'm doing some other things, and making mistakes (.... ehm... I'm making them on purpose ;-)
So I'm fixing the error messages I do not like as they are, trying to make them more helpful.

Just a trivial task (but may be annoying).
Currently in error.H we comment an error name with its string: isn't this a pointless duplication of code?