sympy/sympy — pull request #1957 by cheatiiit (2013-04-01 02:04:37+00:00)
Title: Changed integrate_primitive_polynomial from recursive to iterative 

Solved the cases such as risch_integrate(log(x),x)

Earlier
>>risch_integrate(log(x),x)
RuntimeError: maximum recursion depth exceeded while calling a Python object

Now
>>risch_integrate(log(x),x)
fives answer within few seconds without any recursion limit getting exceeded