DrBayes (https://github.com/ntoronto/drbayes https://github.com/ntoronto/drbayes) is another interesting probabilistic programming language. It implements measu

DrBayes (https://github.com/ntoronto/drbayes https://github.com/ntoronto/drbayes) is another interesting probabilistic programming language. It implements measure-theoretic probability in Racket, so it's not limited to what you can express with probability density functions and standard distributions -- you can condition a random variable on any measurable subset of the probability space, for example, so you could condition Y on 0 < X < 3, which wouldn't be possible to evaluate with density functions. Or you can construct random variables which have no density function. I'm not sure this has great practical use, but it's a very interesting system.