This code was quickly put up to solve the Pi-Campus competition for March 2018 in Rome.
The requirement was to compute as many decimal digits as possible for the π constant, within a 30-minutes timeframe.
I barely sketched the code to make the computation and didn't submit any answer, but I spent some extra time later on to finish the job.
I am really impressed by the result of using CReal haskell arbitrary precision types, which actually was the real show-stopper for me, being
yet unexperienced with real-life coding in haskell.
The current solution was tested to produce 1000 digits in less than a minute, but could be pushed on to produce more using more terms of the mathematical series to compute the number.
It's based on the BBP formula, though rather interesting solutions
exists based on simpler and possibly faster decompositions using arctan functions.