Hi, I'm the guilty party who added \ to Sage notation in the first place, and I would definitely vote to *remove* it. I wish I had never added it in the first place. Nils has some very good points!
In retrospect, I wish we had a "fully supported" way of using Sage entirely without the preparser, but that's another discussion. It's important in the longterm for interoperability with the rest of the Python ecosystem. By "fully supported", I perhaps just mean better documentation (e.g., a switch for the reference and other docs that shows all examples in a way that works without the preparser). -- William On Wed, Sep 27, 2023 at 3:09 PM John H Palmieri <jhpalmier...@gmail.com> wrote: > > Okay, so maybe we should open this to other options: should we get rid of > preparsing "\" into "BackslashOperator"? > > For what it's worth, I removed the line defining `_backslash_` in > binary_tree.py and and I only say one doctest failure in any obvious places > (combinat and thematic_tutorials). So it's not even used much. Same for > matroids. > > I think that using \ to escape characters in strings still works, but > line-continuation does not: in Sage, these fail: > > sage: a = 3 + \ > > and > > sage: \ > > whereas in pure Python, such backslashes would be treated as > line-continuations. It should be possible to fix this while keeping the > current preparser behavior for "\" in the middle of a line. Or as Nils > proposes, getting rid of the current preparser behavior should also solve it. > > On Wednesday, September 27, 2023 at 2:44:19 PM UTC-7 Nils Bruin wrote: >> >> I'm quite strongly against because it collides with a well-established >> meaning of `\` in python: escape character. It's used to avoid command >> termination by newline in things like formulas (as "\<newline", which gets >> parsed as whitespace rather than command termination outside of brackets). >> >> I'm in fact rather shocked that `\` in sage already doesn't work as it's >> supposed to in python but instead gets substituted as "BackslashOperator()". >> >> Searching the codebase currently only shows "_backslash_" implemented on >> matroid, matrix, and binary_tree, so extinguishing it should be doable. We >> should definitely not entrench its use further. >> >> If you want to write your denominator first, you can already do ~2 * 3 . I >> think that's already sufficiently perverse that we don't need another way to >> spell that. >> On Wednesday, 27 September 2023 at 12:16:57 UTC-7 David Joyner wrote: >>> >>> On Wed, Sep 27, 2023 at 2:32 PM John H Palmieri <jhpalm...@gmail.com> wrote: >>>> >>>> The github issue #36060 (https://github.com/sagemath/sage/issues/36060) >>>> proposes adding a backslash operator for Sage integers, so that "2 \ 3" >>>> will return the same as "3 / 2". Do you support this? >>>> >>> >>> I'm not for or against. However, I don't see the problem that implementing >>> this "\" is going to solve. The ticket suggests that users will naturally >>> type 2\3 instead of 3/2, if I am reading between the lines correctly. >>> >>>> >>>> BackslashOperator is defined in "sage/misc/misc.py", and the preparser >>>> converts "A \ b" to the appropriate Python code. The docstring for >>>> BackslashOperator says "Implements Matlab-style backslash operator for >>>> solving systems A \ b". >>>> >>>> It seems pretty innocuous to me — in fact I don't care much either way — >>>> but since Sage integers are so ubiquitous, it seems like a good idea to >>>> ask before implementing it. >>>> >>>> -- >>>> John >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "sage-devel" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to sage-devel+...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/sage-devel/3f157aa4-74cd-4c5c-bc76-f198c6417432n%40googlegroups.com. > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/941e7314-5f78-454a-9017-fe752c630233n%40googlegroups.com. -- William (http://wstein.org) -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CACLE5GCOEcwTqhz60StnPUfAoLcBGRt9%3D9fvskC3D61weCBpyw%40mail.gmail.com.
