arrow-core-data / arrow.typeclasses / Semiring
Semiring
interface Semiring<A>
The Semiring type class for a given type A combines both a commutative additive Monoid and a multiplicative Monoid.
It requires the multiplicative Monoid to distribute over the additive one. The operations of the multiplicative Monoid have been renamed to
one and combineMultiplicate for easier use.
(a.combineMultiplicate(b)).combineMultiplicate(c) == a.combineMultiplicate(b.combineMultiplicate(c))
The one value serves exactly like the empty function for an additive Monoid, just adapted for the multiplicative version. This forms the following law:
combineMultiplicate(x, one) == combineMultiplicate(one, x) == x
Please note that the empty function has been renamed to zero to get a consistent naming style inside the semiring.
Currently, Semiring instances are defined for all available number types.
Examples
Here a some examples:
import arrow.core.extensions.*
fun main(args: Array<String>) {
val result =
//sampleStart
Int.semiring().run { 1.combine(2) }
//sampleEnd
println(result)
}
import arrow.core.extensions.*
fun main(args: Array<String>) {
val result =
//sampleStart
Int.semiring().run { 2.combineMultiplicate(3) }
//sampleEnd
println(result)
}
The type class Semiring also has support for the + * syntax:
import arrow.core.Option
import arrow.core.extensions.*
fun main(args: Array<String>) {
val result =
//sampleStart
Int.semiring().run {
1 + 2
}
//sampleEnd
println(result)
}
import arrow.core.Option
import arrow.core.extensions.*
fun main(args: Array<String>) {
val result =
//sampleStart
Int.semiring().run {
2 * 3
}
//sampleEnd
println(result)
}
Functions
| combine | abstract fun A.combine(b: A): A |
| combineMultiplicate | Multiplicatively combine two A values.abstract fun A.combineMultiplicate(b: A): A |
| maybeCombineAddition | Maybe additively combine two A values.open fun A?.maybeCombineAddition(b: A?): A |
| maybeCombineMultiplicate | Maybe multiplicatively combine two A values.open fun A?.maybeCombineMultiplicate(b: A?): A |
| one | A one value for this Aabstract fun one(): A |
| plus | open operator fun A.plus(b: A): A |
| times | open operator fun A.times(b: A): A |
| zero | A zero value for this Aabstract fun zero(): A |