Program for calculating the square root of numbers

I need a programmer. It requires writing a program to calculate the square root of numbers. Product requirements with the tc. user:
(1) Functionality: roots are not only arithmetic, from zero, complex, long numbers, given accuracy, analytical.
(2) Error resistance
(3) GUI (taking into account accuracy and multilinguality management).
(4) Polylingualism
(5) Cross-platformity