evaluation path for x^y ?

[newbie nullzwei <newbie-02 gmx de>]

 
hello @all,

for private fun, Calc / Excel compatibility and easier cross-system-testing I'd like to implement evaluation of '= (-8)^(1/3)' -> '-2'.

I managed it for 'power' ( by patching goffice and plugins/fn-math/functions, but despite 'EXPR_OP_EXP' seems piped through gnm_power it still produces #NUM!.

can anyone describe the code path for '^' or assume where I might be wrong?

TIA for any help.

P.S. I do not want to start a discussion if odd roots from negative are 'good', allowed or mathematical correct ... the web is full of such ...