Changes between Initial Version and Version 2 of Ticket #17160


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Timestamp:
10/15/14 15:28:51 (5 years ago)
Author:
nthiery
Comment:

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  • Ticket #17160

    • Property Cc tscrim added
    • Property Component changed from PLEASE CHANGE to categories
    • Property Type changed from PLEASE CHANGE to enhancement
  • Ticket #17160 – Description

    initial v2  
     1This introduce an axiom FinitelyGeneratedAsMagma, as well as related
     2categories with axioms for magmas, semigroups and groups::
     3{{{
     4    sage: Groups().FinitelyGeneratedAsMagma()
     5    Category of finitely generated groups
     6}}}
     7For ease of notations, when there is no ambiguity, one can do::
     8{{{
     9    sage: Groups().FinitelyGenerated()
     10    Category of finitely generated groups
     11}}}
     12
     13One motivation for this change (for #8678) is that finite semigroups
     14in Sage used to be automatically endowed with an ``EnumeratedSets``
     15structure; the default enumeration is then obtained by iteratively
     16multiplying the semigroup generators. This forced any finite semigroup
     17to either implement an enumeration, or provide semigroup generators;
     18this was often inconvenient.
     19
     20Instead, finite semigroups that provide a distinguished finite set of
     21generators with ``semigroup_generators`` should now explicitly declare
     22themselves in the category of ``FinitelyGeneratedSemigroups``:
     23{{{
     24    sage: Semigroups().FinitelyGenerated()
     25    Category of finitely generated semigroups
     26}}}
     27This is a backward incompatible change.