Comment #19 on issue 1467 by asmeurer: sorting values with imaginary
numbers in radical
http://code.google.com/p/sympy/issues/detail?id=1467
OK, so I was looking for sorted([3, I]) instead of sorted([3, sqrt(I)]).
Based on a quick git bisect, the second one
was fixed with this commit:
b3f7e6bbae92ee0cf7c286a7d26ce0df899e62c6 is first bad commit
commit b3f7e6bbae92ee0cf7c286a7d26ce0df899e62c6
Author: Chris Smith <smi...@gmail.com>
Date: Fri Oct 16 08:32:59 2009 +0545
1634: better comparisons and minor code edit
== sympy\core\basic.py
o Smarter comparison for relationals implemented:
Here is an interesting example where one thing works
and one doesn't, even though they are (to the human)
almost the same:
In [124]: pi < 0
Out[124]: False
In [125]: pi > 0
Out[125]: -pi < 0
pi<0 is recognized as a number comparison and goes to
lt of numbers.py whereas -pi is an expression and calls
up the basic.py lt routine.
This patch makes the basic relational operators return
a True or False if the sign of the quantities involved
can be determined. This will result in more answers
rather than restatments ('True" instead of "-pi < 0").
o In as_coeff, "expr" was changed to "args" to avoid confusion
== sympy\core\tests\test_basic.py
test smarter relational tests
:040000 040000 271608692dfbe701891b5d540821080cf26b1923
6d2aed5dc2aab4e6febdbf980c3daab97c5106e5 M sympy
Also, I didn't notice:
In [3]: 3<I
Out[3]: False
In [4]: I<3
Out[4]: False
So this is not as bad as before, though it leads to non-canonical results:
In [11]: sorted([sqrt(I), 3])
Out[11]:
⎡4 ⎽⎽⎽⎽ ⎤
⎣╲╱ -1 , 3⎦
In [12]: sorted([3, sqrt(I)])
Out[12]:
⎡ 4 ⎽⎽⎽⎽⎤
⎣3, ╲╱ -1 ⎦
At any rate, this should be fixed:
In [7]: bool(x<y)
Out[7]: True
In [8]: bool(y<x)
Out[8]: False
Or at least make it so x<y isn't a Lt class (see above comment).
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