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scalolli/EitherTravserse.scala

Created May 31, 2018 18:34
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Either traverse cats
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EitherTravserse.scala
import cats.implicits._
def parseInt(s: String): Either[NumberFormatException, Int] = Either.catchOnly[NumberFormatException](s.toInt)
List("1", "2", "3").traverse(parseInt)
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This fails with compilation errors:

<console>:16: error: no type parameters for method traverse: (f: String => G[B])(implicit evidence$1: cats.Applicative[G])G[List[B]] exist so that it can be applied to arguments (String => Either[NumberFormatException,Int])
 --- because ---
argument expression's type is not compatible with formal parameter type;
 found   : String => Either[NumberFormatException,Int]
 required: String => ?G[?B]

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Just put -Ypartial-unification in scalacOptions dumb ass !

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