Boolean operators and C++ code generation

[Dan Goodman]

Hi all,

I just found a bug in code generation with Boolean operators. For
example, the sympy expression x&y ought to generate the C++ code x&&y
but it actually generates And(x,y). I have a fix for this to add to
sympy.printing.ccode.CCodePrinter, the extra methods:

def _print_And(self, expr):
PREC = precedence(expr)
return '&&'.join(self.parenthesize(a, PREC) for a in
expr.args)
def _print_Or(self, expr):
PREC = precedence(expr)
return '||'.join(self.parenthesize(a, PREC) for a in
expr.args)
def _print_Not(self, expr):
PREC = precedence(expr)
return '!'+self.parenthesize(expr.args[0], PREC)

I don't mess around with sympy internals much, so I might be using
self.parenthesize and precedence wrong here (it certainly seems to
create too many parentheses like this), but it does at least seem to
work.

Dan Goodman

[Ondrej Certik]

Hi Dan!

Thanks for the fix. If possible, could you please send it as a git
patch? We'll review it and push it in.

Ondrej

[Aaron S. Meurer]

You'll also need to add tests for the changed behavior. Just add assertions to the relevant place in a test_*.py file that would fail before the patch but passes now. You can verify it by running $ setup.py test

Thanks,
Aaron Meurer

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[Dan Goodman]

Hi,

Unfortunately I don't have the time for the git patch/test writing at
the moment. Indeed, I've never even used git! :) This was more like a
slightly-more-helpful-than-usual bug report than a proper patch. It's
probably not even 100% correct (for example x&y generates (x)&&(y)
rather than x&&y and I have no idea why or what I should have
written). Sorry, hope it was of some use anyway!

Dan

[Aaron S. Meurer]

Well, thanks anyway. I created an issue for it so it won't get lost:
http://code.google.com/p/sympy/issues/detail?id=1834

By the way, Ondrej has some good git patch tutorials here if you are ever interested:
http://code.google.com/p/sympy/wiki/GitTutorials

Aaron Meurer

[Toon Verstraelen]

I've posted patches on the issue tracker. (also for precedence of boolean operators). Dan,
can you try these? It comes down to these commands:

cd somedir
git clone git://git.sympy.org/sympy.git
cd sympy

(download the patches in this directory)

git apply 0001-Precedence-for-boolean-operators-And-Or-and-Not.patch
git apply 0002-Fix-boolean-operatures-in-ccode.patch

(run python, from sympy import *, and try it out)

cheers,

Toon

--
Dr. ir. Toon Verstraelen
Center for Molecular Modeling
Ghent University
Technologiepark 903,
B9052 Zwijnaarde
Belgium
Tel: +32 9 264 65 56
E-mail: Toon.Ver...@UGent.be
http://molmod.UGent.be/
http://molmod.UGent.be/code/

[Dan Goodman]

Toon, that works perfectly for me.

Aaron - yeah, I really should learn to use git some time soon, it
seems to be what all the cool kids are using these days. Not now
though, 3 papers to write by the end of March! :/

Thanks everyone for this fantastic package by the way!

Dan

[Ondrej Certik]

On Tue, Feb 16, 2010 at 6:49 AM, Dan Goodman
<dg.googl...@thesamovar.net> wrote:
> Toon, that works perfectly for me.
>
> Aaron - yeah, I really should learn to use git some time soon, it
> seems to be what all the cool kids are using these days. Not now
> though, 3 papers to write by the end of March! :/

Write your papers in git then --- that's what I do. :)

>
> Thanks everyone for this fantastic package by the way!

Thanks and thanks for your report!

Ondrej