#4485: notebook -- implicit multiplication is broken in the notebook but works
on
the command line (sage-3.1.4)
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Reporter: was | Owner: boothby
Type: defect | Status: new
Priority: major | Milestone: sage-3.2.1
Component: notebook | Resolution:
Keywords: |
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Comment (by was):
{{{
OK, I've thought about it, and see now that there is no way
that implicit multiplication was ever even *implemented*
for the notebook! Just to illustrate what is going on, note
that if in the notebook you type
implicit_multiplication(True)
preparse('3x')
you get as output
'Integer(3)*x'
which illustrates that the implicit_multiplication command works fine in
the actual Sage worksheet process. The problem is that the preparsing of
the input for each cell of the notebook is *not* done in that subprocess!
It's done by the worksheet server process itself, before the input is ever
sent to the subprocess.
There are some approaches to fixing this and I'm not happy really about
any of them:
1. Make it so the whole notebook server has an implicit_multiplication
mode. This is absurd since some users might want it and some not.
Alternatively, make it so the notebook server has a mode flag for each
worksheet. That's bad too since that mode can't be set via user input (by
typing in cells) unless we fully parse all input before passing it on for
evaluation -- i.e., that's a stupid idea which will result in great pain.
The other option, would be to have some GUI checkbox or something, and
just give an error if one types in the input box
"implicit_multiplication". This would be inconsistent and maybe busy, but
would probably work. The inconsistency would be huge, since, e.g., if
somebody writes a 30 line script like this:
...
implicit_multiplication(True)
...
3x + 1
...
and just *pastes* it into the notebook, it will suddenly not work. Which
will be really annoying.
2. Change how the Sage notebook evaluates code blocks. Instead of
preparsing input before sending it off to be evaluated by the worksheet
subprocess, somehow send a chunck of non-preparsed code off, and a command
that says "preparse this then evaluate it".
3. Make sage query the subprocess for its implicit_multiplication state
before every single evaluation -- this would be idiotic and slow down the
server a lot. Not an option.
I think 2 is the best option, but it will not be easy to implement, and
making this change scares me. It feels like the sort of change that could
introduce numerous subtle bugs, and result in nontrivial degredation in
functionality -- for example, maybe source code ?? inspection of user-
defined functions in the notebook might no longer work.
Incidentally, here is a workaround to make it so you can input an
expression using implicit multiplication in the notebook.
implicit_multiplication(True)
sage_eval('3x^3 + 4/5 x + 1', globals())
3*x^3 + 4*x/5 + 1
I'm not going to do anything further on this without some feedback
from Robert Bradshaw (who implemented implicit multiplication)
and/or Mike Hansen who I think knows the relevant part of the
notebook code well enough to have a comment about what
I wrote above.
-- William
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4485#comment:1>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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