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Algebras implementation which isn't based on nested type hierarchy
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import scala.language.reflectiveCalls | |
type Nullary[A] = Unit | |
type Unary[A] = A | |
type Binary[A] = (A, A) | |
trait Algebra { | |
type Set | |
type Operation[F[_]] = F[Set] => Set | |
type NullaryOperation = Operation[Nullary] | |
type UnaryOperation = Operation[Unary] | |
type BinaryOperation = Operation[Binary] | |
} | |
type AdditiveNeutral = Algebra { val zero: NullaryOperation } | |
type AdditiveInverse = Algebra { val minus: UnaryOperation } | |
type AdditiveSemigroup = Algebra { val add: BinaryOperation } | |
type AdditiveMonoid = AdditiveNeutral with AdditiveSemigroup | |
type AdditiveGroup = AdditiveMonoid with AdditiveInverse | |
type MultiplicativeNeutral = Algebra { val one: NullaryOperation } | |
type MultiplicativeInverse = Algebra { val inverse: UnaryOperation } | |
type MultiplicativeSemigroup = Algebra { val mul: BinaryOperation } | |
type MultiplicativeMonoid = MultiplicativeNeutral with MultiplicativeSemigroup | |
type MultiplicativeGroup = MultiplicativeMonoid with MultiplicativeInverse | |
type Ring = AdditiveGroup with MultiplicativeMonoid | |
type Field = Ring with MultiplicativeInverse | |
implicit class NumericOps[A](private val value: A) { | |
def +(another: A)(implicit alg: AdditiveSemigroup { type Set = A }): A = alg.add((value, another)) | |
def *(another: A)(implicit alg: MultiplicativeSemigroup { type Set = A }): A = alg.mul((value, another)) | |
def -(another: A)(implicit alg: AdditiveGroup { type Set = A }): A = alg.add((value, alg.minus(another))) | |
def /(another: A)(implicit alg: MultiplicativeGroup { type Set = A }): A = alg.mul((value, alg.inverse(another))) | |
} | |
def test[A](a1: A, a2: A)(implicit field: Field { type Set = A }) = | |
(a1 + a2) - (a1 * a2 / a2) | |
implicit object intField extends Algebra { | |
type Set = Int | |
val zero: NullaryOperation = _ => 0 | |
val minus: UnaryOperation = x => -x | |
val add: BinaryOperation = { case (x, y) => x + y } | |
val one: NullaryOperation = _ => 1 | |
val inverse: UnaryOperation = x => 1 / x | |
val mul: BinaryOperation = { case (x, y) => x * y } | |
} | |
println(test(10, 5)) |
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