As you will have noticed, this page of news and comments have been added to the Troll dice roller page. I will use the news page to announce new developments and features to Troll. New entries will be added at the top of the page.

I will start by mentioning a few changes that I have (silently) made over the last few months.

As some of you may have noticed, the Troll the dice! button has been replaced by two separate buttons for rolling dice and calculating probabilities. Additionally, you can now specify how many digits of precision you want shown for the probabilities and you can choose if the second column shows the probability of the result being ≥, ≤, > or < than the value shown. The first column and the graph will always show the probability of the result being equal to the shown value.

Another change involves the Troll language itself. ?p, where p is a probability written as a 0 followed by a decimal point and at least one digit (e.g., 0.141592) will return 1 with probability p and the empty collection with probability 1-p. It is usually combined with if-then-else, such as in if ?0.312 then 7 else 9, which will choose 7 with probability 0.312 and 9 otherwise. The ? operation allows choice with arbitrary probabilities, where the previous operations (such as choose only allows choice with uniform probability.

An earlier attempt at optimisation introduced some bugs. I thought I had fixed them, but one remained for foreach which means that use of an assigned variable inside foreach sometimes gave wrong probabilities. This is fixed now.

If you have made any probability calculations using foreach in the last couple of months, you should probably redo them to be sure you get the right result.

I have added two new operators: minimal and maximal. They are similar to min and max, but where min returns a single copy of the minimal value, minimal returns all minimal values. For example, min{2,2,3} returns 2 but minimal{2,2,3} returns 2 2. Similarly, maximal returns all maximal values. Note that minimal and maximal, unlike min and max, are defined on empty collections, where they return the empty collection.

The probability calculator now allows text operations when calculating probabilities. Beware that this will list all possible strings that can be generated, so don't use it for, for example, the d20 character definition, as that can generate 17⁶=24137569 different strings.

It is, however useful if you want to return two independent values (such as width and height of a roll), as you can return the pair of x and y by writing.

 "(" || 'x || "," || 'y || ")" 

A recently made over-eager optimization made some expressions like d6-d6 generate wrong probability distributions. It is fixed now.