Sb/print local rings #2806
Sb/print local rings #2806
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Codecov Report
@@ Coverage Diff @@
## master #2806 +/- ##
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- Coverage 73.67% 73.64% -0.04%
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Files 455 455
Lines 64527 64569 +42
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+ Hits 47541 47552 +11
- Misses 16986 17017 +31 |
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New printing looks very good: right balance between necessary information and sufficiently compact presentation. Thank you.
I left a few comments on particular cases of output, which struck me as odd or weird at first glance or for which I would have expected something else. These are to be understood as markers for further discussion, not as complaints against this PR.
In particular, we should discuss at some point whether the affine space encoded as Spec(k[x]) and the affine space encoded as Spec(k[x]/<0>) or as V() should be printed in the same or different ways. Same question for the empty set and V(1) etc.
| to [x1, x2, x3] affine 3-space over QQ | ||
| given by the pullback function | ||
| x1 -> 0 | ||
| x2 -> x2 | ||
| x3 -> x3 | ||
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| julia> graph(f) | ||
| (Spec of quotient of multivariate polynomial ring, Morphism: spec of quotient of multivariate polynomial ring -> spec of quotient of multivariate polynomial ring, Morphism: spec of quotient of multivariate polynomial ring -> affine 3-space over QQ with coordinates [x1, x2, x3]) | ||
| (V(x1, -x1, x2 - x2, x3 - x3), Morphism: V(x1, -x1, x2 - x2, x3 - x3) -> V(x1), Morphism: V(x1, -x1, x2 - x2, x3 - x3) -> affine 3-space over QQ with coordinates [x1, x2, x3]) |
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Something is going wrong with the variable names here. This keeps the new output from being more helpful than the old one.
(I am aware that it is a non-trivial design choice, what to do in the case of products with the same variable names.)
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One could choose new names for the codomain in case of an automorphism. Say x,y,t and x',y',t'
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Yes this would be a viable solution for this case, but what about morphisms between rings which only happen to have the same variable names by chance? We should discuss this point directly (not on github).
| by ideal(x^2 - y^2 + z^2) | ||
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| julia> singular_locus(A3) | ||
| (Spec of quotient of multivariate polynomial ring, Morphism: spec of quotient of multivariate polynomial ring -> spec of multivariate polynomial ring) | ||
| (V(1), Morphism: V(1) -> affine 3-space) |
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Again just a remark on the design decision, certainly not a change request:
empty set would be more user friendlc than V(1) -- but has the same mathematical content. But on the other hand large insatisfiable systems of equations might hide an empty set, whereas computing that it is the empty set may be expensive. One way out might be to check whether the set itself knows that it is the empty set and only then print èmpty set` and print the generating set otherwise.
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