Singleton types for Literals are implemented using a marker trait called a LiteralHash.
trait LiteralHash[X] {
type TypeHash <: Dense
type ValueHash <: Dense
val value: X
}
The TypeHash is a natural number representing the type of the literal and the ValueHash is a natural number representing
the value of the literal. This way, literals that have the same truncated binary representation, like 42, 42L and
-2147483606 have different TypeHashs and are therefore differentiable.
The companion object contains implicit conversions to build a LiteralHash[X] from a literal of type X. Usage is
very straightforward. For example,
scala> import typequux._
import typequux._
scala> import Dense._
import Dense._
scala> def lh(i: LiteralHash[Int])(implicit ev0: DenseRep[i.ValueHash], ev1: DenseRep[i.TypeHash]) = (ev0.v, ev1.v)
lh: (i: typequux.LiteralHash[Int])(implicit ev0: typequux.Dense.DenseRep[i.ValueHash], implicit ev1: typequux.Dense.DenseRep[i.TypeHash])(Long, Long)
scala> lh(12)
res0: (Long, Long) = (12,9)
scala> lh(15)
res1: (Long, Long) = (15,9)
scala> lh(15000)
res2: (Long, Long) = (15000,9)
scala> lh(-15000)
res3: (Long, Long) = (2147468648,8)
scala> def lh2(i: LiteralHash[Int], j: LiteralHash[Int])(implicit ev: DenseRep[i.ValueHash * j.ValueHash]) = ev.v
lh2: (i: typequux.LiteralHash[Int], j: typequux.LiteralHash[Int])(implicit ev: typequux.Dense.DenseRep[typequux.Dense.*[i.ValueHash,j.ValueHash]])Long
scala> lh2(12, 10)
res4: Long = 120
scala> lh2(14, 2)
res5: Long = 28