claireneveu / tbox 1.1.1

BSD 3-clause "New" or "Revised" License GitHub

Simple type-class boxes for constructing heterogenous lists.

Scala versions: 2.11

TBox provides a data-type to erase types to constraints (context bounds). Instances of the type-class used are automatically created for TBox.

Getting TBox

If you're using SBT, add the following to your build file.

libraryDependencies += "com.claireneveu" %% "tbox" % "1.1.0"

API Documentation

Full API documentation is available here.

How to Use

Given Int, String, and Double you can erase their type to Show and thus pass around a well-typed list of objects that can be displayed.

val showables : List[TBox[Show]] = List(TBox[Show](1), TBox[Show]("two"), TBox[Show](3.0))
showables.foreach(show)
// Prints
// > 1
// > two
// > 3.0

Limitations

TBox can only create instances for single-parameter type-classes where each abstract method takes a value of the parameterized type as an argument.

Therefore you cannot instantiate a TBox[Num] (as defined in Haskell) because fromInteger cannot be defined in Num[TBox[Num]].