dart_dice_parser

Description:

dart dice parser

dart_dice_parser #





A dart library for parsing dice notation (e.g. "2d6+4"). Supports advantage/disadvantage, exploding die, and other variations.
Example #

import 'package:dart_dice_parser/dart_dice_parser.dart';

void main() {
// Create a roller for D20 advantage (roll 2d20, keep highest).
final d20adv = DiceExpression.create('2d20 kh');

stdout.writeln(d20adv.roll());
// outputs:
// ((2d20)kh) => RollResult(total: 15, results: [15] , metadata: {dropped: [8], rolled: [8, 15]})

stdout.writeln(d20adv.roll());
// outputs:
// ((2d20)kh) => RollResult(total: 20, results: [20] , metadata: {dropped: [5], rolled: [5, 20]})
}
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Random Number Generator #
By default, Random.secure() is used. You can select other RNGs when creating the
dice expression. Random() is faster than Random.secure(), so if you're doing lots of rolls
for use cases where security doesn't matter, you may want to use Random().
// uses Random.secure()
final diceExpr1 = DiceExpression.create('2d20 kh');

// uses supplied RNG.
final diceExpr2 = DiceExpression.create('2d20 kh', Random());

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Dice Notation #
Examples: #


2d20 #cf #cs

roll 2d20, result will include counts of critical successes (20) and failures (1)



advantage

2d20-L -- drop lowest
2d20k, 2d20kh -- keep highest



disadvantage

2d20-H -- drop highest
2d20-kl -- keep lowest



(2d10+3d20)-L3 -- roll 2d10 and 3d20, combine the two results lists, and drop lowest 3 results


20d10-<3->8# -- roll 20 d10, drop any less than 3 or greater than 8 and count the number of remaining dice


Supported notation #


2d6 -- roll 2 dice of 6 sides


special dice variations:

4dF -- roll 4 fudge dice (sides: [-1, -1, 0, 0, 1, 1])
1d% -- roll 1 percentile dice (equivalent to 1d100)
1D66 -- roll 1 D66, aka 1d6*10 + 1d6

NOTE: you must use uppercase D66, lowercase d66 will be interpreted as a 66-sided die





exploding dice

4d6! -- roll 4 6-sided dice, explode if max (6) is rolled (re-roll and include in results)

4d6 !=5 or 4d6!5 -- explode a roll if equal to 5
4d6 !>=4 - explode if >= 4
4d6 !<=2 - explode if <=2
4d6 !>5 - explode if > 5
4d6 !<2 - explode if <2
To explode only once, use syntax !o

4d6 !o<5







compounding dice (Shadowrun, L5R, etc). Similar to exploding, but the additional rolls for each
dice are added together as a single "roll"

5d6 !! -- roll 5 6-sided dice, compound

5d6 !!=5 or 5d6!5 -- compound a roll if equal to 5
5d6 !!>=4 - compound if >= 4
5d6 !!<=4 - compound if <= 4
5d6 !!>5 - compound if > 5
5d6 !!<3 - compound if < 3
To compound only once, use syntax !!o

5d6 !!o<2







re-rolling dice:

4d4 r2 -- roll 4d4, re-roll any result = 2
4d4 r=2 -- roll 4d4, re-roll any result = 2
4d4 r<=2 -- roll 4d4, re-roll any <= 2
4d4 r>=3 -- roll 4d4, re-roll any >= 3
4d4 r<2 -- roll 4d4, re-roll any < 2
4d4 r>3 -- roll 4d4, re-roll any > 3
To reroll only once, use syntax ro

4d4 ro<2





keeping dice:

3d20 k 2 -- roll 3d20, keep 2 highest
3d20 kh 2 -- roll 3d20, keep 2 highest
3d20 kl 2 -- roll 3d20, keep 2 lowest



dropping dice:

4d6 -H -- roll 4d6, drop 1 highest
4d6 -L -- roll 4d6, drop 1 lowest
4d6 -H2 -- roll 4d6, drop 2 highest
4d6 -L2 -- roll 4d6, drop 2 lowest
4d6 ->5 -- roll 4d6, drop any results > 5
4d6 -<2 -- roll 4d6, drop any results < 2
4d6 ->=5 -- roll 4d6, drop any results >= 5
4d6 -<=2 -- roll 4d6, drop any results <= 2
4d6 -=1 -- roll 4d6, drop any results equal to 1
NOTE: the drop operators have higher precedence than
the arithmetic operators; 4d10-L2+2 is equivalent to (4d10-L2)+2
NOTE: drop is not subtraction.

4d6 - 3 -- roll 4d6, subtract 3
4d6 - 2d6 -- roll 4d6, subtract the result of rolling 2d6





cap/clamp:

4d20 C<5 -- roll 4d20, change any value < 5 to 5
4d20 C>15 -- roll 4d20, change any value > 15 to 15



operations on dice rolls:

counting:

4d6 # -- how many results?

For example, you might use this to count # of dice above a target. (5d10 -<6)# -- roll 5 d10, drop any less than 6, count results


4d6 #>3 -- roll 4d6, count any > 3
4d6 #<3 -- roll 4d6, count any < 3
4d6 #>=5 -- roll 4d6, count any >= 5
4d6 #<=2 -- roll 4d6, count any <= 2
4d6 #=5 -- roll 4d6, count any equal to 5


counting (critical) success/failures

A normal count operation # discards the rolled dice and changes the result to be the count

For example, 2d6#<=3 rolls [3,4] then counts which results are <=3 , returning [1]


But, sometimes you want to be able to count successes/failures without discarding the dice rolls.
In this case, use modifiers #s, #f, #cs, #cf to add metadata to the results.

6d6 #f<=2 #s>=5 #cs6 -- roll 6d6, count results <= 2 as failures, >= 5 as successes, and =6 as critical successes.

returns a result like: RollResult(total: 22, results: [6, 2, 1, 5, 3, 5] {failures: {count: 2, target: #f<=2}, successes: {count: 3, target: #s>=5}, critSuccesses: {count: 1, target: #cs6}})









arithmetic operations

parenthesis for order of operations
addition is a little special -- could be a sum of ints, or it can be used to aggregate results of multiple dice rolls

Addition of integers is the usual sum

4+5
2d6 + 1


Addition of roll results combines the results (use parens to ensure the order of operations is what you desire)

(5d6+5d10)-L2 -- roll 5d6 and 5d10, and from aggregate results drop the lowest 2.
5d6+5d10-L2 -- roll 5d6 and 5d10, and from only the 5d10 results drop the lowest 2. equivalent to 5d6+(5d10-L2)




* for multiplication
- for subtraction
numbers must be integers
division is not supported.



CLI Usage #
There's no executable in bin, but there's an example CLI at example/main.dart.
❯ dart example/main.dart '3d6'
(3d6) => RollResult(total: 9, results: [4, 3, 2])


# run N number of rolls
❯ dart example/main.dart -n6 '3d6'
(3d6) => RollResult(total: 14, results: [6, 6, 2])
(3d6) => RollResult(total: 8, results: [2, 5, 1])
(3d6) => RollResult(total: 12, results: [3, 5, 4])
(3d6) => RollResult(total: 16, results: [5, 5, 6])
(3d6) => RollResult(total: 15, results: [3, 6, 6])
(3d6) => RollResult(total: 6, results: [1, 1, 4])


# show statistics for a dice expression
❯ dart example/main.dart -s '3d6'
{mean: 10.5, stddev: 2.97, min: 3, max: 18, count: 10000, histogram: {3: 49, 4: 121, 5: 273, 6: 461, 7: 727, 8: 961, 9: 1153, 10: 1182, 11: 1272, 12: 1151, 13: 952, 14: 733, 15: 486, 16: 289, 17: 154, 18: 36}}

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Features and bugs #
Please file feature requests and bugs at the issue tracker.