New interface with OEIS

[williamstein]

The sloane_find command, which parses output of a webpage, is broken for years due to the Sloane sequence webpage being rewritten. It silently always finds nothing.

sage: sloane_find([1,1,2,3,5,8,13,21], nresults=1)
[]

The aim of this ticket is to propose a new interface with OEIS http://oeis.org/

Apply:

• attachment: trac_10358-oeis-tm_rebase.patch
• attachment: trac_10358-oeis-review_1-tm.patch
• attachment: trac_10358-oeis-review_2-tm.patch
• attachment: trac_10358-oeis-review_3-nc-tm.patch​

Depends on #15245

CC: @sagetrac-sage-combinat @williamstein @kini @jpflori @sagetrac-chrisjamesberg @VivianePons

Component: combinatorics

Keywords: Cernay2012 days49

Author: Thierry Monteil

Reviewer: Nathann Cohen

Merged: sage-5.13.beta2

Issue created by migration from https://trac.sagemath.org/ticket/10358

[williamstein]

comment:2

Crap, this is a dup of #10056

[sagetrac-tmonteil]

comment:3

Hi,

the aim of #10056 was to migrate every url in sage that was dealing with Sloane's database at once (not only sloane_find()), hence this is not really a duplicate. The issue here is that oeis changed their html templates, so the sage parsers are not working anymore. I just coded a new parser, which you can see working on the combinat repository (sloane_new_website_parsers-tm.patch).

I added the more atomic functions in sage/databases/sloane.py (the documentation still needs to be fixed):

• sloane_discover() which discovers which sequences correspond to some list of integers.
• sloane_first_terms() which returns the first terms of the sequence.
• sloane_description() which returns the one line description of the sequence.

I don't really know what to do with the broken functions:

• parse_sequence() is completely dead and now useless. Should it now raise a deprecation warning ?
• sloane_sequence() and sloane_find() are broken, but maybe some users still need them, should i make them working again as a combination of the first 3 functions ?

Also, maybe all those functions should be renamed by replacing sloane by oeis ? This may be too early since i guess most people know more about Sloane than about oeis. In such a case, what is the procedure/convention to ensure backward compatibility ?

At the end, we could have a daily crontab to check when the oeis changes its html template, and adapt the parsers accordingly. Better, we could ask them to provide an online standard query system, but if i understand a discussion in the nmbrthry mailing-list, this may not be their whish.

Ciao,
Thierry