Write a program to evaluate postfix expressions containing complex numbers using a stack. The algorithm for evaluating a postfix expression requires a stack of complex numbers. The pseudocode for evaluating postfix expressions is given below:

while not end of expression

switch next token

case complex number:

push the value onto the stack

case operator:

pop two operands from the stack

evaluate operation

push result onto the stack

pop the final result off the stack

Each complex number will all be enclosed in a pair of parentheses. The operators permitted include +, - and *. You may assume that all expressions are syntactically correct. 
The user should be allowed to enter and evaluate any number of expressions.