Changes between Initial Version and Version 4 of Ticket #17671


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Timestamp:
01/25/15 23:50:35 (5 years ago)
Author:
vdelecroix
Comment:

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  • Ticket #17671

    • Property Status changed from new to needs_review
    • Property Commit changed from to d8a03d7fa1dd0e401adbae8e2a16ccbfb1902392
    • Property Dependencies changed from to #17673
    • Property Branch changed from to u/vdelecroix/17671
  • Ticket #17671 – Description

    initial v4  
    77}}}
    88
    9 We implement a `xgcd` for the `QuotientFields` category in order to fix that (there was a `gcd` here without a `xgcd`).
     9We implement a `xgcd` for the `QuotientFields` category in order to fix that (there was a `gcd` here without a `xgcd`). We also check that for PID the `gcd` and `xgcd` agree by implementing a `_test_gcd_vs_xgcd`. With that branch
     10{{{
     11sage: xgcd(6/1,2/1)
     12(2, 0, 1)
     13sage: xgcd(5/2, 3/4)
     14(1/4, -1/2, 2)
     15}}}
     16which is consistent with `gcd`.
     17
     18QUESTIONS:
     19
     201. In the previous implementation of gcd in `sage.categories.fields` there is a backward compatibility weirdness
     21  {{{
     22  sage: gcd(2.0, 4.0)
     23  2
     24  sage: gcd(2.0, 4.0).parent()
     25  Integer Ring
     26  }}}
     27  For the moment, I propagated this to `lcm` and `xgcd`.
     28
     292. 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` (see [https://groups.google.com/forum/#!topic/sage-devel/JV8fCPUqTzo this sage-devel thread])