def rect(func, a, b):
    """
    
    Approximation to contribution of a finite domain to the integral, 
    evaluated as a rough rectangle
    
    *args*:

        - **func**: executable to evaluate
        
        - **a**: float, start of interval
        
        - **b**: float, end of interval
        
    *return*: 

        - **recsum**: (complex) float approximated area of the region under
        function between **a** and **b**
    
    ***
    """
    mid = (a + b) / 2.0
    jac = abs(b - a) / 6.0
    recsum = jac * (func(a) + 4 * func(mid) + func(b))
    return recsum
