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object EnvEffetWithoutSubtyping { | |
import EnvEffetWithoutSubtyping.Alg1.HasAlg1 | |
import EnvEffetWithoutSubtyping.Alg2.HasAlg2 | |
import EnvEffetWithoutSubtyping.Alg3.HasAlg3 | |
trait Alg1 | |
object Alg1 { | |
// Describe an env intersection type which contains an Alg1 type | |
trait HasAlg1[E] { | |
def alg1(e: E): Alg1 | |
} | |
} | |
trait Alg2 | |
object Alg2 { | |
trait HasAlg2[E] { | |
def alg2(e: E): Alg2 | |
} | |
} | |
trait Alg3 | |
object Alg3 { | |
trait HasAlg3[E] { | |
def alg3(e: E): Alg3 | |
} | |
} | |
// Intersection types are case classes instead of mixed types | |
final case class SmallEnv(alg1: Alg1, alg2: Alg2) | |
object SmallEnv { | |
implicit val env1: HasAlg1[SmallEnv] = _.alg1 | |
implicit val env2: HasAlg2[SmallEnv] = _.alg2 | |
} | |
final case class BigEnv(alg1: Alg1, alg2: Alg2, alg3: Alg3) | |
object BigEnv { | |
// Define its HasX type classes, something to do with lenses here | |
implicit val env1: HasAlg1[BigEnv] = _.alg1 | |
implicit val env2: HasAlg2[BigEnv] = _.alg2 | |
implicit val env3: HasAlg3[BigEnv] = _.alg3 | |
} | |
// No inference here | |
def program[Env: HasAlg1: HasAlg2: HasAlg3](): Reader[Env, Unit] = { | |
// Fine grained dependencies | |
def innerF1[E: HasAlg1]: Reader[E, Unit] = ??? | |
def innerF2[E: HasAlg2]: Reader[E, Unit] = ??? | |
def innerF3[E: HasAlg1: HasAlg2]: Reader[E, Unit] = ??? | |
def innerF4[E: HasAlg1: HasAlg2: HasAlg3]: Reader[E, Unit] = ??? | |
for { | |
_ <- innerF1 // Possible to thread Env here | |
_ <- innerF2 | |
_ <- innerF3 | |
_ <- innerF4 | |
} yield () | |
} | |
val env: BigEnv = ??? | |
program[BigEnv].run(env) | |
} |
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