Philippe Sigaud: >Less than 1s is impressive.< To compare, on the Ideone site the third Python version (Python 2.6.4 + Psyco) takes 1.46s and max 88 MB (this is where what Don has said about D bignums is important): http://ideone.com/5NvzR >Maybe with lazy int delegates ?< Right, but the devil is in details. Bye, bearophile