Changes between Version 12 and Version 20 of Ticket #17671


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Timestamp:
01/28/15 12:51:14 (5 years ago)
Author:
vdelecroix
Comment:

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  • Ticket #17671

    • Property Dependencies changed from #17673 to #17673, #17675
    • Property Commit changed from 1d84c4a9160533338cb19a8df2351cd0fc9d79d0 to c6db5f832b23d29026019de5306472a25e591279
  • Ticket #17671 – Description

    v12 v20  
    17172. We fix the `xgcd` for trivial cases in `rings.polynomial.polynomial_element_generic.Polynomial_generic_field` in order that `gcd` and `xgcd` agree for them.
    18183. We introduce a generic test `_test_gcd_vs_xgcd` in the category `PrincipalIdealDomains` to ensure the compatibility of `gcd` and `xgcd`.
    19 
    20 QUESTIONS:
    21 
    22 1. In the previous implementation of gcd in `sage.categories.fields` there is a backward compatibility weirdness
     194. Modify the previous behavior for real numbers (which was present because of mysterious backward compatibility reasons)
    2320  {{{
    2421  sage: gcd(2.0, 4.0)
     
    2724  Integer Ring
    2825  }}}
    29   For the moment, I propagated this to `lcm` and `xgcd`.
     26  Now we have
     27  {{{
     28  sage: gcd(2.0, 4.0)
     29  1.00000000000000
     30  sage: gcd(2.0, 4.0).parent()
     31  Real Field with 53 bits of precision
     32  }}}
    3033
    31 2. There is a method `xgcd` implemented for univariate polynomial over ZZ. ~~This is not a proper name since it has nothing to do with `gcd`~~ This might not be the best name since the first term is not the gcd in general (see [https://groups.google.com/forum/#!topic/sage-devel/JV8fCPUqTzo this sage-devel thread])
     34
     35Note:
     36
     37There is a method `xgcd` implemented for univariate polynomial over ZZ. ~~This is not a proper name since it has nothing to do with `gcd`~~ This might not be the best name since the first term is not the gcd in general (see [https://groups.google.com/forum/#!topic/sage-devel/JV8fCPUqTzo this sage-devel thread] and #17674)