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June 22, 2017 06:05
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Scala, проба работы с implicit + tagged type + annotation
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import scala.annotation.StaticAnnotation | |
import scala.language.experimental.macros | |
import scala.reflect.macros.whitebox.Context | |
final class currency extends StaticAnnotation { | |
def macroTransform(annottees: Any*): Any = macro currencyMacro.impl | |
} | |
object currencyMacro { | |
def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = { | |
import c.universe._ | |
def addTree(tpl: Template, tree: Tree): Template = addTreeList(tpl, List(tree)) | |
def addTreeList(tpl: Template, trees: List[Tree]): Template = | |
Template(tpl.parents, tpl.self, trees ::: tpl.body) | |
val inputs = annottees.map(_.tree).toList | |
val expandees = inputs.head match { | |
case param@ModuleDef(mods, name, tpl) => | |
val currencyName = s" ${name.decodedName.toString}" | |
val ops = | |
q""" | |
implicit class Ops(val __v:Type) extends AnyVal { | |
def pretty: String = __v.toString + $currencyName | |
} | |
""" | |
val tn = name.decodedName.toTypeName | |
val typ = q"type $tn = $name.Type" | |
val fn = TermName(s"doubleTo${name.decodedName}") | |
val cast = q"implicit def $fn(x : Double) : $tn = $name(x)" | |
val newParam = ModuleDef(mods, name, addTree(tpl, ops)) | |
List(newParam, typ, cast) | |
case _ => | |
inputs | |
} | |
val outputs = expandees | |
c.Expr[Any](Block(outputs, Literal(Constant(())))) | |
} | |
} | |
final class invertRate extends StaticAnnotation { | |
def macroTransform(annottees: Any*): Any = macro invertRateMacro.impl | |
} | |
object invertRateMacro { | |
def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = { | |
import c.universe._ | |
val inputs = annottees.map(_.tree).toList | |
val expandees = inputs.head match { | |
case param@ValDef(mods, name, t1, t2) => | |
val invertedFun = t2 match { | |
case Apply(fun, List(v)) => | |
val TypeApply(fName, List(dt, from, to)) = fun | |
val invertedFName = TypeApply(fName, List(dt, to, from)) | |
Apply(invertedFName, List(q"1.0/$v")) | |
} | |
val newValName = TermName(s"${name.decodedName.toString}Inv") | |
val newVal = q"implicit val $newValName = $invertedFun" | |
List(param, newVal) | |
} | |
val outputs = expandees | |
c.Expr[Any](Block(outputs, Literal(Constant(())))) | |
} | |
} |
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import supertagged._ | |
object Test extends App { | |
object currency { | |
trait Currency extends TaggedType[Double] | |
@currency object Rub extends Currency | |
@currency object Usd extends Currency | |
@currency object Eur extends Currency | |
} | |
import currency._ | |
trait Rate[T, C1, C2] { | |
def apply(from : C1)(implicit m : Numeric[T], c : (T) => C2) : C2 | |
} | |
def exchangeRate[T, C1, C2]( rate : T) = new Rate[T, C1, C2] { | |
def apply(from : C1)(implicit m : Numeric[T], c : (T) => C2): C2 = m.times(from.asInstanceOf[T], rate : T) | |
} | |
implicit class Converter[C1, T](val arg1: T @@ C1) extends AnyVal { | |
def ++[C2](arg2 : T @@ C2)(implicit r : Rate[T, T @@ C1, T @@ C2], m : Fractional[T], f1 : (T) => T @@ C1, f2 : (T) => T @@ C2 ) = f1(m.plus(arg1, r(arg2))) | |
def --[C2](arg2 : T @@ C2)(implicit r : Rate[T, T @@ C1, T @@ C2], m : Fractional[T], f1 : (T) => T @@ C1, f2 : (T) => T @@ C2 ) = f1(m.minus(arg1, r(arg2))) | |
} | |
implicit val rubToRub = exchangeRate[Double, Rub, Rub](1) | |
implicit val usdToUsd = exchangeRate[Double, Usd, Usd](1) | |
@invertRate implicit val rubToUsd = exchangeRate[Double, Rub, Usd](32) | |
@invertRate implicit val rubToEur = exchangeRate[Double, Rub, Eur](60) | |
val c1 : Rub = Rub @@ 40.0 | |
val c2 : Usd = Usd @@ 1.0 | |
val c3 : Eur = Eur @@ 1.0 | |
println(c1 pretty) | |
println(c2 pretty) | |
println((c1 ++ c2) pretty) | |
println((c1 -- c2) pretty) | |
println((c3 ++ c1) pretty) | |
} |
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