Ok: first of all, Clojure has outstandingly the best core library I've seen. I am awed by how wonderfully the protocol approach makes data structures, and the good taste applied to getting an API that's reasonably minimal and wonderfully complete. I've not posted before because I've had nothing to ask - everything is super-clear, especially now I have a copy of JoC. But I would suggest that there is one easily corrected area where things are imperfect: -
One of the big advantages of functional coding to me is rock solid testability - same inputs, same outputs; easy to test, easy to debug. Obviously psuedo-random numbers and io present problems with this. Now, the normal way for an API to discourage something problematic is to make it difficult, and to encourage correct behavoiur by making it easy. So list's lack of nth but possession of first, second rest and last shout out "Do NOT use for random access!" while vector's api says "Use me instead!" Now we come to rand, rand-int, rand-nth. They're the easiest things to use for their purpose, so they shout "Use me!" But.. they break the repeatability paradigm. Because they use Java's default random number generator instance, which has a private and unsettable seed, you can't get repeatabilty. In Java, this isn't actually too awful because you can instantiate an rng of your own and use it in just the same way - but if you do this in clojure, bang goes your rand-nth. Yes, the problem is one you can easily solve with a few minutes coding. But an api should gently lure into doing things the right way rather than wrong one - so wouldn't it be a good idea to add change the standard api to include a function that takes a seed? A random that allows you to see the last "seed" would be even better. That way when you get => (foo-uses-rand "bar') ..crazy result *sometimes* then => (def wrong (get-last-rand-seed)) would give you the seed needed to repeat the last call to any random fn. So you could fix your code and verify by re-seeding with "wrong" and repeating the function call. To me this seems a nice low-impact solution. It wouldn't make repeatability bullet proof, but I'd suggest it would be an easily implemented mild improvement for a future version of clojure. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
