Comment 4 for bug 288446

While you are correct in saying that the odd roots will give a single, non-complex answer I'm not sure how one would go about identifying the odd roots in a reasonable, consistent fashion.

I would assume that the bracketed exponent is evaluated initially to a decimal. For the most part you could invert the decimal and get the base of the fraction and using that determine if the root will be even or odd. However for irrational (currently the check is against non-integers so these are caught) and repeating fractions this number is only approximate, which, when used to evaluate the parity of root could introduce errors.

I think that dealing with non-integer exponents of negative bases is beyond the scope of gcalctool and more in line with something like Rascal, Genius, Qalculate, or even Octave. However, I understand that since this is the default shipping calculator with many Gnome desktops there may be a desire to see it's functionality increased.