Well...
My calculator implimentation works and passes all the first test cases.
Then in the Fixed test cases one returns wrong result, and in the random ones one throws exception.

I printed out the expressions given as input strings and tried the code and my caclulator, my PC's
built in calculator and I found the same result!!
But in codewars still refuses to accept my implimentation.

Please contact me to send you the code to check it for your selves it works for all the test cases.
I have worked had for it to work and I would like to get the points I deserve thanks a lot.
Please respond as soon as possible!!

Kostis

code may be working correctly but it is not easy to read, better documentation or variable names would be a nice thing to add for readability :)