# ExDiceRoller
[](https://travis-ci.org/rishenko/ex_dice_roller)
[](https://coveralls.io/github/rishenko/ex_dice_roller?branch=master)
[](https://hex.pm/packages/ex_dice_roller)
Provides a [DSL](https://en.wikipedia.org/wiki/Domain-specific_language) and
various options for calculating both simple and complex dice rolling equations.
## Features
Main Features:
* Generates dice rolls with any number of dice and sides of dice.
* Supports common math operators: `+`, `-`, `*`, `/`, `%` modulo, `^` exponentiation
* Supports `+` and `-` unary operators.
* Supports using single-letter variables in expressions that can be given values
upon invocation, such as `1dx+y`.
* Supports parenthetically grouped expressions such as `(1d4)d(3d6)-(1d4+7)`.
* Supports compiling dice rolls into reuseable anonymous functions.
* Introduces a new sigil, `~a`. This can be used as a shorthand for compiling
and/or rolling dice rolls, such as `~a/1d6+2-(1d4)d6/`.
Other Features:
* Supports exploding dice.
* Supports 'keeping' the result of each die roll in an expression. The list
of values can then be used in a manner similar to list comprehensions in
expressions with other mathematical operators and lists.
* Optional support for caching compiled rolls. This can be especially useful
in an application that generates various rolls during runtime.
## Installation
Add `:ex_dice_roller` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:ex_dice_roller, "~> 0.5.0-alpha"}
]
end
```
Next, run:
```
$ mix deps.get
```
## General Usage
ExDiceRoller supports a variety of possible dice roll permutations that can be
used in your application.
```elixir
iex> ExDiceRoller.roll("1")
#=> 1
iex> ExDiceRoller.roll("1+2")
#=> 3
iex> ExDiceRoller.roll("1d6")
#=> 1
iex> ExDiceRoller.roll("1d20-(5*6)")
#=> -28
# rolls of rolls
iex> ExDiceRoller.roll("1d4d6")
#=> 10
iex> ExDiceRoller.roll("(1d4+2)d((5*6)d20-5)", [])
#=> 566
# variable usage
iex> ExDiceRoller.roll("1dx+y", [x: 20, y: 13])
#=> 16
# save each die roll
iex> ExDiceRoller.roll("3d8", [], [:keep])
#=> [3, 3, 4]
# save each die roll, adding each die's counterpart to the other
iex> ExDiceRoller.roll("5d1+5d10", [], [:keep])
#=> [3, 5, 7, 7, 2]
iex> ExDiceRoller.roll("5d1+5d10", [], [:keep, :explode])
#=> [7, 3, 2, 4, 10]
iex> ExDiceRoller.roll("1d6", [], [:explode])
#=> 9
```
## Compiled Expressions
Parsed expressions can be compiled into a single, executable anonymous
function. This function can be reused again and again, with any dice rolls
being randomized and calculated for each call.
Note that while `ExDiceRoller.roll/1` always returns integers,
`ExDiceRoller.execute/1` will return either floats or integers.
```elixir
iex> {:ok, roll_fun} = ExDiceRoller.compile("1d6 - (3d10)d5 + (1d50)/5")
#=> {:ok, #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>}
iex> ExDiceRoller.execute(roll_fun)
#=> -16
iex> roll_fun.([], [])
#=> -43
iex> {:ok, roll_fun} = ExDiceRoller.compile("1dx+10")
#=> {:ok, #Function<8.36233920/1 in ExDiceRoller.Compiler.compile_op/5>}
iex> ExDiceRoller.execute(roll_fun, [x: 5])
#=> 12
iex> ExDiceRoller.execute(roll_fun, x: "10d100")
#=> 523
iex> ExDiceRoller.execute(roll_fun, [x: "10d100"], [:keep])
#=> [11, 11, 16, 25, 27, 16, 55, 24, 50, 12]
```
## Sigil Usage
ExDiceRoller introduces a new sigil, `~a`, with the same set of options as `ExDiceRoller.roll/3`.
```elixir
# import the sigil inside any module that will use it
iex> import ExDiceRoller.Sigil
#=> ExDiceRoller.Sigil
# using the sigil without any options will generate a compiled function
iex> fun = ~a/1d6+3/
#=> #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>
# the function can then be executed as any other ExDiceRoller.compile/0
iex> ExDiceRoller.execute(fun)
#=> 6
# compiles the roll and invokes it
iex> ~a/1d2+3/r
#=> 4
# compiles the roll and invokes it with exploding dice
iex> ~a/1d2+2/re
#=> 9
# function passed directly to roller
iex> ExDiceRoller.roll(~a/2d8-2/)
#=> 3
# keeping dice rolls and adding 5 to each
iex> ~a/5d1+5/k
#=> [6, 6, 6, 6, 6]
# keeping dice rolls from both sides, adding each value to its counterpart
iex> ~a/5d1+5d10/k
#=> [8, 7, 5, 2, 11]
```
## Caching Support
```elixir
iex> ExDiceRoller.start_cache()
#=> {:ok, ExDiceRoller.Cache}
iex> ExDiceRoller.roll("xdy-2d4", [x: 10, y: 5], [:cache])
#=> 34
iex> ExDiceRoller.Cache.all()
#=> [{"xdy-2d4", #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>}]
iex> ExDiceRoller.roll("xdy-2d4", [x: 10, y: "2d6"], [:cache])
#=> 29
iex> ExDiceRoller.Cache.all()
#=> [{"xdy-2d4", #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>}]
iex> ExDiceRoller.roll("1d6+3d4", [], [:cache])
#=> 10
iex> ExDiceRoller.Cache.all()
#=> [
#=> {"xdy-2d4", #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>},
#=> {"1d6+3d4", #Function<1.86580672/2 in ExDiceRoller.Compiler.compile/1>}
#=> ]
```
## How It Works
1. ExDiceRoller utilizes Erlang's [leex](http://erlang.org/doc/man/leex.html)
library to tokenize a given dice roll string.
2. The tokens are then passed to [yecc](http://erlang.org/doc/man/yecc.html)
which parses the tokens into a concrete syntax tree.
3. The syntax tree is then interpreted through recursive navigation.
4. During interpretation:
1. Any basic numerical values are calculated.
2. Any dice rolls are converted into anonymous functions.
3. Any mathematical operations using numbers are calculated.
4. Any mathematical operations using expressions are converted into
anonymous functions.
dice rolls are converted into anonymous functions.
5. The results of interpretation are then wrapped by a final anonymous
function.
6. This final anonymous function is then executed and the value returned.
```elixir
iex(3)> expr = "(1d4+2)d((5*6)d20-5)"
"(1d4+2)d((5*6)d20-5)"
iex(4)> {:ok, tokens} = ExDiceRoller.tokenize(expr)
{:ok,
[
{:"(", 1, '('},
{:digit, 1, '1'},
{:roll, 1, 'd'},
{:digit, 1, '4'},
{:basic_operator, 1, '+'},
{:digit, 1, '2'},
{:")", 1, ')'},
{:roll, 1, 'd'},
{:"(", 1, '('},
{:"(", 1, '('},
{:digit, 1, '5'},
{:complex_operator, 1, '*'},
{:digit, 1, '6'},
{:")", 1, ')'},
{:roll, 1, 'd'},
{:digit, 1, '20'},
{:basic_operator, 1, '-'},
{:digit, 1, '5'},
{:")", 1, ')'}
]}
iex(5)> {:ok, ast} = ExDiceRoller.parse(tokens)
{:ok,
{:roll,
{{:operator, '+'},
{:roll, {:digit, '1'}, {:digit, '4'}},
{:digit, '2'}},
{{:operator, '-'},
{:roll,
{{:operator, '*'}, {:digit, '5'}, {:digit, '6'}},
{:digit, '20'}},
{:digit, '5'}}}}
iex(6)> {:ok, roll_fun} = ExDiceRoller.compile(ast)
{:ok, #Function<12.11371143/0 in ExDiceRoller.Compiler.compile_roll/4>}
iex(7)> roll_fun.([], [])
739
iex(8)> roll_fun.([], [])
905
iex(9)> ExDiceRoller.Compiler.fun_info(roll_fun)
{#Function<9.16543174/1 in ExDiceRoller.Compiler.compile_roll/4>,
:"-compile_roll/4-fun-0-",
[
{#Function<1.16543174/1 in ExDiceRoller.Compiler.compile_add/4>,
:"-compile_add/4-fun-1-",
[
{#Function<12.16543174/1 in ExDiceRoller.Compiler.compile_roll/4>,
:"-compile_roll/4-fun-3-", [1, 4]},
2
]},
{#Function<14.16543174/1 in ExDiceRoller.Compiler.compile_sub/4>,
:"-compile_sub/4-fun-1-",
[
{#Function<12.16543174/1 in ExDiceRoller.Compiler.compile_roll/4>,
:"-compile_roll/4-fun-3-", [30, 20]},
5
]}
]}
```
## Test Coverage and More
* [ex_coveralls](https://github.com/parroty/excoveralls) provides test coverage
metrics.
* [credo](https://github.com/rrrene/credo) is used for static code analysis.
* Documentation, generated by [ex_doc](https://github.com/elixir-lang/ex_doc),
is [available at hex.pm](https://hexdocs.pm/ex_dice_roller/).
## License
ExDiceRoller source code is released under Apache 2 License.
