Eurydice is a half-baked programming language disguised as a dice engine. Its syntax is designed to be ergonomic for dice rolls while still remaining reasonably self-consistent.

For example:

> d20

9

calls the builtin d (dice roll) function with the argument 20. Functions with only one argument don't require parentheses.

> d[1. 4. 5]

4

calls d with the array argument [1. 4. 5], defining the faces of the die.

Rolling multiple dice can be done with:

> 5d20

[9. 20. 14. 4. 8]

which evaluates the expression d20 5 times and stores the results in an array.

You can sum these up using the summation operator ...:

> ...5d20

55

There are a variety of mathematical operators available, currently +, -, *, /, **, and %:

> d20 + 20

29

There are also Boolean operators. They work on numbers as well--0 is false and 1 is true.

> 5(d20 > 10)

[0. 1. 1. 0. 0]

This allows the & operator to double as "minimum" and | to double as "maximum":

> 3 & 6

3

> 3 | 6

6

Sometimes, anonymous functions can come in handy. Take, for example, the built-in "reroll" function, which keeps rolling a die until a specified condition is true:

> reroll (@_ d20), (@x x % 3 = 0)

9

Functions in Eurydice take at most one argument, and multi-argument functions are done using partial application. For instance:

highest 2, 8d8

first evaluates highest 2 and returns a function that, itself, returns the highest 2 elements in the array passed into it. Then that function is called with the results of evaluating 8d8.

This has some benefits. For instance, you can do things like:

drop highest 2, 8d8

This evaluates the highest 2 argument (into a function) and then 8d8 (into an array of 8 numbers), passing both into the drop function. The drop function can then pass the latter into the former and then drop the highest 2 rolls.

Eurydice is something I quickly put together for fun, and there are still a ton of rough edges and a lack of documentation. Let me know if this is something you'd be interested in using!

To start, install the dependencies:

npm install

then start the interactive prompt:

npm run interactive