Paul:
When compiled on a 64 bit machine, this lineint r = uniform(0, mobs.length);
".length" returns a size_t, and 0 is an int. uniform() probably decides to unify those types to a size_t. A size_t is 32 bit on 32 bit machines and 64 bits on 64 bit machines. But D "int" is always a 32 bit signed integer. D allows implicit assignment of a 32 bit size_t to int but not a 64 bit size_t to an int. I agree that it's a bit of a mess.
Bye, bearophile