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S.Zero.is_imaginary should be True? #7649

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skirpichev opened this issue Jun 27, 2014 · 8 comments · May be fixed by #23739
Open

S.Zero.is_imaginary should be True? #7649

skirpichev opened this issue Jun 27, 2014 · 8 comments · May be fixed by #23739
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assumptions core

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@skirpichev
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See discussion in #2538 starting from this and #4149.
@smichr
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smichr commented Aug 22, 2014

Having worked more with this I am much more in favor of making S.Zero both real and imaginary, the origin for both real and imaginary scales. Without this, (I*r).is_imaginary for var('r', real=True) has to be None...it would be nice if it were True.

@asmeurer
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To summarize my opinion from the other threads, I think zero should be imaginary, first, because to me this is the natural definition mathematically, and second, because it makes more inferences possible in the assumptions system (the I*r case noted by @smichr is a great example of this).

@smichr smichr mentioned this issue Aug 24, 2014
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asmeurer added a commit to asmeurer/sympy that referenced this issue Sep 28, 2014
@asmeurer
Old assumptions: Add fact for zero to be imaginary
c403f1c 
This only changes assumptions.py, not the corresponding changes throughout
SymPy. See sympy#7649. There are two motivations for this change. First, it makes
more sense mathematically ("imaginary" now means "on the imaginary axis"), and
second, because it makes some more useful deductions possible, such as r*I =
imaginary for r real.
@pelegm
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pelegm commented Jan 2, 2015

I think we can remove the "needs decision" label. This looks like we've already decided this should be fixed. I've tried, but quickly ran into import issues, so I think I'll leave it for the veterans.

@skirpichev
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I think we can remove the "needs decision" label.

I think so. For reference, see #8134.

@skirpichev skirpichev removed the Needs Decision This needs discussion to resolve an undecided issue before further work can be done. label Jan 2, 2015
skirpichev added a commit to diofant/diofant that referenced this issue Mar 10, 2015
@skirpichev
Set 0.is_imaginary to be True
26551c5 
fix sympy/sympy#7649
skirpichev added a commit to diofant/diofant that referenced this issue Mar 10, 2015
@skirpichev
Set 0.is_imaginary to be True
04c72f6 
fix sympy/sympy#7649
@debugger22
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Did we agree on both real and imaginary?

@asmeurer
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I think it was pretty well agreed that zero should be imaginary (but this was never implemented IIRC). It should not be difficult to fix (much easier than changing the behavior of oo.is_real). I would start with fixing it, so you can get an idea of how the old assumptions work.

@debugger22
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Thanks! I think Sergey has already fixed it in his fork of sympy.

@asmeurer asmeurer mentioned this issue May 26, 2015
Open
@jksuom jksuom mentioned this issue Jun 1, 2015
Merged
leosartaj added a commit to leosartaj/sympy that referenced this issue Jun 1, 2015
@leosartaj
added reference to sympy#7649
b9953ef
debugger22 pushed a commit to debugger22/sympy that referenced this issue Jun 23, 2015
@skirpichev @debugger22
Set 0.is_imaginary to be True
77e747b 
fix sympy#7649
@AnishShah
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Hi, this issue is still not resolved. @skirpichev are you still working on this? I would like to work on this if you're not

skirpichev added a commit to skirpichev/diofant that referenced this issue Nov 2, 2016
@skirpichev
Add regression tests & mention closed issues
74ade76 
    close sympy/sympy#3112 (MrvAsympt was added in diofant#6)
    close sympy/sympy#9173 (test was added in 5a510ac)
    close sympy/sympy#9808 (fixed in 09e539b)
    close sympy/sympy#9341 (fixed in af98a00)
    close sympy/sympy#9908 (fixed in cc3fa8d)
    close sympy/sympy#6171 (test added in d278031)
    close sympy/sympy#9276 (diagnose_imports.py removed in ab8c535)
    close sympy/sympy#10201 (fixed in 0d0fc5f)
    close sympy/sympy#9057 (test was added in 8290a0c)
    close sympy/sympy#11159 (test was added in ffb76cb)
    close sympy/sympy#2839 (new AST transformers are used, see diofant#278 and diofant#167)
    close sympy/sympy#11081 (see ed01e16 and bb92329)
    close sympy/sympy#10974 (see 73fc425)
    close sympy/sympy#10806 (test in 539929a)
    close sympy/sympy#10801 (test in 2fe3da5)
    close sympy/sympy#9549 (test in 88bdefa)
    close sympy/sympy#4231 (test was added in fb411d5)
    close sympy/sympy#8634 (see 2fcbb58)
    close sympy/sympy#8481 (see 1ef20d3)
    close sympy/sympy#9956 (fixed in a34735f)
    close sympy/sympy#9747 (see e117c60)
    close sympy/sympy#7853 (see 3e4fbed)
    close sympy/sympy#9634 (see 2be03f5)
    close sympy/sympy#8500 (fixed in diofant#104 and finally in diofant#316)
    close sympy/sympy#9192 (see 9bf622f)
    close sympy/sympy#7130 (see e068fa3)
    close sympy/sympy#8514 (see b2d543b)
    close sympy/sympy#9334 (see 90de625)
    close sympy/sympy#8229 (see 9755b89)
    close sympy/sympy#8061 (see 7054f06)
    close sympy/sympy#7872 (tested in diofant#6)
    close sympy/sympy#3496 (tested in test_log_symbolic)
    close sympy/sympy#2929 (see da7db7a)
    close sympy/sympy#8203 (oo is not a real, see diofant#36)
    close sympy/sympy#7649 (0 is imaginary since diofant#8)
    close sympy/sympy#7256 (fixed in c0a4549)
    close sympy/sympy#6783 (see cb28d63)
    close sympy/sympy#5662 (is_integer issue fixed in 6bfa9f8, there is no is_bounded anymore)
    close sympy/sympy#5295 (fixed with diofant#354)
    close sympy/sympy#4856 (we now have flake/pep tests)
    close sympy/sympy#4555 (flake8 enabled after diofant#214)
    close sympy/sympy#5773 (cmp_to_key removed after diofant#164 and c9acbf0)
    close sympy/sympy#5484 (see above)

    Added regression tests:
    from https://groups.google.com/forum/#!topic/sympy/LkTMQKC_BOw
    fixes sympy/sympy#8825 (probably via diofant#209)
    fixes sympy/sympy#8635
    fixes sympy/sympy#8157
    fixes sympy/sympy#7872
    fixes sympy/sympy#7599
    fixes sympy/sympy#6179
    fixes sympy/sympy#5415
    fixes sympy/sympy#2865
    fixes sympy/sympy#5907
    fixes sympy/sympy#11722

    Closes diofant#347
skirpichev added a commit to skirpichev/diofant that referenced this issue Nov 2, 2016
@skirpichev
Add regression tests & mention closed issues
48c035e 
    close sympy/sympy#3112 (MrvAsympt was added in diofant#6)
    close sympy/sympy#9173 (test was added in 5a510ac)
    close sympy/sympy#9808 (fixed in 09e539b)
    close sympy/sympy#9341 (fixed in af98a00)
    close sympy/sympy#9908 (fixed in cc3fa8d)
    close sympy/sympy#6171 (test added in d278031)
    close sympy/sympy#9276 (diagnose_imports.py removed in ab8c535)
    close sympy/sympy#10201 (fixed in 0d0fc5f)
    close sympy/sympy#9057 (test was added in 8290a0c)
    close sympy/sympy#11159 (test was added in ffb76cb)
    close sympy/sympy#2839 (new AST transformers are used, see diofant#278 and diofant#167)
    close sympy/sympy#11081 (see ed01e16 and bb92329)
    close sympy/sympy#10974 (see 73fc425)
    close sympy/sympy#10806 (test in 539929a)
    close sympy/sympy#10801 (test in 2fe3da5)
    close sympy/sympy#9549 (test in 88bdefa)
    close sympy/sympy#4231 (test was added in fb411d5)
    close sympy/sympy#8634 (see 2fcbb58)
    close sympy/sympy#8481 (see 1ef20d3)
    close sympy/sympy#9956 (fixed in a34735f)
    close sympy/sympy#9747 (see e117c60)
    close sympy/sympy#7853 (see 3e4fbed)
    close sympy/sympy#9634 (see 2be03f5)
    close sympy/sympy#8500 (fixed in diofant#104 and finally in diofant#316)
    close sympy/sympy#9192 (see 9bf622f)
    close sympy/sympy#7130 (see e068fa3)
    close sympy/sympy#8514 (see b2d543b)
    close sympy/sympy#9334 (see 90de625)
    close sympy/sympy#8229 (see 9755b89)
    close sympy/sympy#8061 (see 7054f06)
    close sympy/sympy#7872 (tested in diofant#6)
    close sympy/sympy#3496 (tested in test_log_symbolic)
    close sympy/sympy#2929 (see da7db7a)
    close sympy/sympy#8203 (oo is not a real, see diofant#36)
    close sympy/sympy#7649 (0 is imaginary since diofant#8)
    close sympy/sympy#7256 (fixed in c0a4549)
    close sympy/sympy#6783 (see cb28d63)
    close sympy/sympy#5662 (is_integer issue fixed in 6bfa9f8, there is no is_bounded anymore)
    close sympy/sympy#5295 (fixed with diofant#354)
    close sympy/sympy#4856 (we now have flake/pep tests)
    close sympy/sympy#4555 (flake8 enabled after diofant#214)
    close sympy/sympy#5773 (cmp_to_key removed after diofant#164 and c9acbf0)
    close sympy/sympy#5484 (see above)

    Added regression tests:
    from https://groups.google.com/forum/#!topic/sympy/LkTMQKC_BOw
    fixes sympy/sympy#8825 (probably via diofant#209)
    fixes sympy/sympy#8635
    fixes sympy/sympy#8157
    fixes sympy/sympy#7872
    fixes sympy/sympy#7599
    fixes sympy/sympy#6179
    fixes sympy/sympy#5415
    fixes sympy/sympy#2865
    fixes sympy/sympy#5907
    fixes sympy/sympy#11722

    Closes diofant#347
@asmeurer asmeurer mentioned this issue Jul 26, 2018
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@oscargus oscargus mentioned this issue Jul 27, 2019
Open
@asmeurer asmeurer mentioned this issue Jun 29, 2022
Merged
@oscarbenjamin oscarbenjamin linked a pull request Jul 8, 2022 that will close this issue
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fix(core): make zero imaginary in the assumptions oscarbenjamin/sympy
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@asmeurer @smichr @skirpichev @debugger22 @AnishShah @pelegm