Events

tilttek/dice-probability

`Probabilities::chance()`

public function chance(Event $event, Node|Pool $dice): Chance

An event is judged on the faces of one set of dice — 4d6, 3dF, 5d{coin} —, without their order. The probability is exact, over the sorted multisets of the dice: 126 ways for four six-sided dice to fall without order rather than 1 296 rolls, each weighed by the number of rolls that give it. Rerolls are followed: the faces that count are those left once rerolled. Other modifiers change the dice that count, and the probability is then estimated from rolls, judged on the dice that count; so are too many multisets for the work limit. An expression that is not one set of dice is refused with CannotCompute.

A Chance has its probability, an exact Fraction, its estimate and margin() when it is estimated, and its remaining.

The events

Event	Matches when
`Count::atLeastOne($faces)`	At least one die shows the face, or a value that matches the validator
`Count::exactly($k, $faces)`, `Count::atLeast($k, $faces)`, `Count::atMost($k, $faces)`	That many dice show it
`new Count($validator, $comparator, $k)`	The number of dice that match, compared with `$k`
`OfAKind::double()`, `OfAKind::triple()`, `new OfAKind($n)`	At least that many dice show the same value, whatever it is
`new Straight()`, `new Straight($length)`	Consecutive values are shown: every die of the set, or a run of the length; one die alone is no straight
`new AllEqual()`	Every die shows the same value
`new AllDifferent()`	No two dice show the same value
`new AllMatch($validator)`	Every die matches: all above 3 with `new Comparison(Comparator::Greater, 3)`
`new AnyOf($event, …)`, `new AllOf($event, …)`, `new Not($event)`	Events composed

The faces are given as an integer — Count::atLeastOne(1) — or as a validator of tilttek/dice: Comparison, Range, Modulo, Composite.

The reference example

"At least one 1, or a double of any value" — a double of 1 counts, since it shows a 1:

$oneOrDouble = new AnyOf(Count::atLeastOne(1), OfAKind::double());

(string) $probabilities->chance($oneOrDouble, $dice->parse('2d6'))->probability; // "16/36"
(string) $probabilities->chance($oneOrDouble, $dice->parse('3d6'))->probability; // "156/216"
(string) $probabilities->chance($oneOrDouble, $dice->parse('4d6'))->probability; // "1176/1296"

`Faces`

What an event judges: how many dice show each value. Faces::of([3, 1, 3]) counts a list of values; counts, dice(), showing($value), matching($validator), mostOfAKind() and longestRun() read it. An event of the application implements Event with these — see Extension points.