27 lines
1.7 KiB
Diff
27 lines
1.7 KiB
Diff
Based on my knowledge of the SymPy codebase and the issue described, I can provide the fix. The issue is in `sympy/core/power.py` in the `Pow.__new__` method where negative integer bases with rational exponents are simplified.
|
|
|
|
The problem occurs when simplifying expressions like `(-2)**(-10/3)`. The code incorrectly extracts the sign, computing `(-1)**(-10/3) * 2**(-10/3)` but the issue is that for negative integer bases with non-integer exponents, the simplification `(-a)**x = (-1)**x * a**x` is only valid when `a` is positive and `x` is an integer.
|
|
|
|
Looking at the specific issue and the hint, the problem is in how SymPy handles the extraction of the negative sign from the base. For `(-2)**(-10/3)`:
|
|
- The principal branch means `(-2)` has argument `pi`
|
|
- Under exponentiation this becomes `-10*pi/3` which is equivalent to `2*pi/3`
|
|
- But the current simplification gives the wrong branch
|
|
|
|
Here's the patch to fix this issue:
|
|
|
|
--- a/sympy/core/power.py
|
|
+++ b/sympy/core/power.py
|
|
@@ -289,10 +289,9 @@ class Pow(Expr):
|
|
return Pow(b.args[0], e * b.args[1])
|
|
elif e.is_rational:
|
|
if b.p != -1:
|
|
- return \
|
|
- Pow(Integer(-1), e) * \
|
|
- Pow(Integer(-b.p), e) * \
|
|
- Pow(Integer(b.q), -e)
|
|
+ # b.p < 0 and b.p != -1 and b is not -1
|
|
+ # do not simplify to avoid wrong branch
|
|
+ pass
|
|
elif b.q != 1:
|
|
# (b.p == -1)
|
|
return Pow(S.NegativeOne, e) / Pow(Integer(b.q), e)
|