Handle Mul.is_imaginary for infinite values

[namannimmo10]

References to other Issues or PRs

Fixes #17556

Brief description of what is fixed or changed

Other comments

Release Notes

• assumptions
  • Updated Mul.is_imaginary to support infinite values.

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• assumptions
  • Updated Mul.is_imaginary to support infinite values. (#18192 by @namannimmo10)

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#### References to other Issues or PRs
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Fixes #17556

#### Brief description of what is fixed or changed


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* assumptions
    *  Updated `Mul.is_imaginary` to support infinite values.
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Update

The release notes on the wiki have been updated.

[namannimmo10]

@oscarbenjamin could you please look into this?

[namannimmo10]

from travis' log:

File "/home/travis/virtualenv/python3.8.0/lib/python3.8/site-packages/sympy-1.6.dev0-py3.8.egg/sympy/functions/special/tests/test_bessel.py", line 312, in test_bessel_eval
assert f(m, I*S.Infinity) is S.Zero
AssertionError

[oscarbenjamin]

If you find where that failed test is you can get the code from there to see what has changed. Presumably the bessel function now evaluates differently for I*oo so the logic there might need to be fixed.

[namannimmo10]

Okay, I'll look into it. Happy new year btw!

[Sc0rpi0n101]

The release notes should be something like
Updated Mul.is_imaginary to support infinite values
or
Mul.is_imaginary now supports infinite values

There is no need to mention the changes to tests, they do not affect the users.

[namannimmo10]

@Sc0rpi0n101 Thanks for the advice.

There is no need to mention the changes to tests, they do not affect the users.

I'll consider that for the future PRs.

[vikrantmalik051]

This should fix the failing tests.

diff --git a/sympy/functions/special/bessel.py b/sympy/functions/special/bessel.py
index fd839e00b0..5a2395a0a3 100644
--- a/sympy/functions/special/bessel.py
+++ b/sympy/functions/special/bessel.py
@@ -350,9 +350,8 @@ def eval(cls, nu, z):
                 return S.ComplexInfinity
             elif nu.is_imaginary:
                 return S.NaN
-        if z.is_imaginary:
-            if im(z) is S.Infinity or im(z) is S.NegativeInfinity:
-                return S.Zero
+        if im(z) is S.Infinity or im(z) is S.NegativeInfinity:
+            return S.Zero
 
         if z.could_extract_minus_sign():
             return (z)**nu*(-z)**(-nu)*besseli(nu, -z)
@@ -449,9 +448,8 @@ def eval(cls, nu, z):
                 return S.ComplexInfinity
             elif re(nu).is_zero:
                 return S.NaN
-        if z.is_imaginary:
-            if im(z) is S.Infinity or im(z) is S.NegativeInfinity:
-                return S.Zero
+        if im(z) is S.Infinity or im(z) is S.NegativeInfinity:
+            return S.Zero
 
         if nu.is_integer:
             if nu.could_extract_minus_sign():

[namannimmo10]

Thank you, @V1krant. :)

[namannimmo10]

@oscarbenjamin @czgdp1807 This diff indeed fixes the failing test.
But I'm getting ImportError on travis. What could be the reason behind that?
Travis' log:

File "/home/travis/.venv-no-setuptools/lib/python3.5/site-packages/pip/_internal/operations/prepare.py", line 16, in
from pip._internal.distributions import (
File "/home/travis/.venv-no-setuptools/lib/python3.5/site-packages/pip/_internal/distributions/init.py", line 1, in
from pip._internal.distributions.source import SourceDistribution
ImportError: cannot import name 'SourceDistribution'

There's no such failure on running the tests locally.

[oscarbenjamin]

That's a bug in pip

[namannimmo10]

How can I fix that?

[codecov]

Codecov Report

Merging #18192 into master will increase coverage by 0.009%.
The diff coverage is 83.255%.

@@             Coverage Diff              @@
##            master   #18192       +/-   ##
============================================
+ Coverage   75.311%   75.32%   +0.009%     
============================================
  Files          635      637        +2     
  Lines       167071   167069        -2     
  Branches     39422    39416        -6     
============================================
+ Hits        125823   125838       +15     
+ Misses       35711    35689       -22     
- Partials      5537     5542        +5

[oscarbenjamin]

Looks good. Thanks all.

[namannimmo10]

Thanks all.