Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 3072 by [email protected]: Limit of a piecewise function
http://code.google.com/p/sympy/issues/detail?id=3072
I get an error when trying to evaluate the limit of a piecewise function.
The following code,
from sympy import *
x = symbols('x')
f1 = Piecewise((0, x<0), (1, True))
f1.limit(x, 0)
produces error
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python26\lib\site-packages\sympy\core\expr.py", line 1722, in
limit
return limit(self, x, xlim, dir)
File "C:\Python26\lib\site-packages\sympy\series\limits.py", line 192, in
limit
r = gruntz(e, z, z0, dir)
File "C:\Python26\lib\site-packages\sympy\series\gruntz.py", line 688, in
gruntz
r = limitinf(e0, z)
File "C:\Python26\lib\site-packages\sympy\core\cache.py", line 101, in
wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "C:\Python26\lib\site-packages\sympy\series\gruntz.py", line 469, in
limitinf
e = e.rewrite('tractable', deep=True)
File "C:\Python26\lib\site-packages\sympy\core\basic.py", line 1186, in
rewrite
return self._eval_rewrite(None, rule, **hints)
File "C:\Python26\lib\site-packages\sympy\core\function.py", line 508, in
_eval_rewrite
args = [ a._eval_rewrite(pattern, rule, **hints) for a in self.args ]
File "C:\Python26\lib\site-packages\sympy\core\function.py", line 508, in
_eval_rewrite
args = [ a._eval_rewrite(pattern, rule, **hints) for a in self.args ]
AttributeError: 'bool' object has no attribute '_eval_rewrite'
This error also appears if direction is specified explicitly, i.e.
f1.limit(x, 0, '-')
f1.limit(x, 0, '+')
By the way, the Heaviside function from the special functions module works
properly:
fH = functions.special.delta_functions.Heaviside(x)
fH.limit(x, 0, '+') # gives 1
fH.limit(x, 0, '-') # gives 0
With best regards, Anton Travleev.
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