seems to me that asking for the "sign" of b^(1/3) in the complex domain
is nonsense. There are 3 cube roots. Let q be one of them; it doesn't
matter which.
then - (1+sqrt(3)*i)*q/2 are the other two. Yes, two. because there
are two sqrt(3).

##
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If you cannot deal with all 3 of them in Sage, then you have a problem
in Sage, regardless of whether asking Maxima for a "sign" leads to
an error.
I think that if Sage requires the power of cylindrical algebraic
decomposition,
which such questions seem to require, then calling Maxima, which does
not have that programmed, is an inadequate step in whatever you
are trying to do,.
Good luck
RJF
On Thursday, August 10, 2017 at 11:37:47 AM UTC-7, Richard_L wrote:
>
> The following string sent to maxima causes a seg-fault and core dump:
>
> >
> /home/rllozes/sage-8.0/local/lib/python2.7/site-packages/sage/interfaces/maxima_lib.py(452)_eval_line()
> 450 line = line[ind_semi+1:]
> 451 if statement:
> 2-> 452 result = ((result + '\n') if result else '') +
> max_to_string(maxima_eval("#$%s$"%statement))
> 453 else:
> 454 statement = line[:ind_dollar]
>
> ipdb> p "#$%s$"%statement
> '#$is
> (equal(-(_SAGE_VAR_r13^2*_SAGE_VAR_r23-_SAGE_VAR_r23^3)/((-_SAGE_VAR_r23^4)+2*_SAGE_VAR_r13^2*_SAGE_VAR_r23^2-_SAGE_VAR_r13^4+_SAGE_VAR_r12^4),0))$'
> ipdb> s
>
>
> ;;;
> ;;; Detected access to protected memory, also kwown as 'bus or
> segmentation fault'.
> ;;; Jumping to the outermost toplevel prompt
> ;;;
>
> ... [elided]
>
> Segmentation fault (core dumped)
>
> NOTE 1: The line numbering corresponds to SageMath version 8.0 and
> Maxima-5.40.0.
> I observe the same behavior with Maxima-5.39.0 but did not
> trace.
>
> NOTE 2: Not visible in the ipdb session are the declarations of the
> variables. So, in addition to the ipdb session, I attach the .sage source.
>
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