Issue 1161: Wrong result if calling Basic.subs() with a dictionary
http://code.google.com/p/sympy/issues/detail?id=1161
Comment #1 by ondrej.certik:
Indeed, great job with the debugging, thanks! This bug is still present
with our
latest git version.
So the problem is that the result of sol.subs() depends on the order of
substitution
(which gets affected for example by using either .subs(m)
or .subs(m.items())).
This is correct:
# sol.subs(m.items())
result = (-c_ + (-e_/a_)**(1/d_))/b_
result.subs(b_, 1) -> -c_ + (-e_/a_)**(1/d_)
result.subs(e_, -3) -> -c_ + (3/a_)**(1/d_)
result.subs(c_, 0) -> (3/a_)**(1/d_)
result.subs(a_, L) -> (3/L)**(1/d_)
result.subs(d_, 0.4) -> 15.5884572681199*(1/L)**2.5
So where exactly is the error here:
# sol.subs(m)
result = (-c_ + (-e_/a_)**(1/d_))/b_
result.subs(d_, 0.4) -> (-c_ + I*e_**2.5*(1/a_)**2.5)/b_
result.subs(a_, L) -> (-c_ + I*e_**2.5*(1/L)**2.5)/b_
result.subs(c_, 0) -> I*e_**2.5*(1/L)**2.5/b_
result.subs(e_, -3) -> -15.5884572681199*(1/L)**2.5/b_
result.subs(b_, 1) -> -15.5884572681199*(1/L)**2.5
on which line? Let's fix that particular substitution and all should start
working again.
Issue attribute updates:
Status: Accepted
Labels: -Priority-Medium Priority-High WrongResult
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