A macro implementation of HList
WORK IN PROGRESS
HLists can be thought as a generalized tuple, i.e. not limited in size. In addition it offers list like operations, such as append, prepend, map, etc.
Here is an example session.
Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37).
Type in expressions to have them evaluated.
Type :help for more information.
scala> import macroHList._
import macroHList._
scala> val l1 = 1 :: "two" :: 3.0 :: HNil
l1: macroHList.::[Int,macroHList.::[String,macroHList.::[Double,macroHList.HNil.type]]] = HList(1, two, 3.0)
scala> l1.reverse
res0: macroHList.::[Double,macroHList.::[String,macroHList.::[Int,macroHList.HNil.type]]] = HList(3.0, two, 1)
scala> l1.toTuple
res1: (Int, String, Double) = (1,two,3.0)
scala> l1 ++ (true :: HNil)
res2: macroHList.::[Int,macroHList.::[String,macroHList.::[Double,macroHList.::[Boolean,macroHList.HNil.type]]]] = HList(1, two, 3.0, true)
scala> import macroHList.Implicits._
import macroHList.Implicits._
scala> (1, "two", 3.0).reverse.toTuple
res4: (Double, String, Int) = (3.0,two,1)For (pure) function memoization, you can use the cached macro just before the function definition, as show after.
Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37).
Type in expressions to have them evaluated.
Type :help for more information.
scala> import macroHList._
import macroHList._
scala> import util._
import util._
scala> def fac(i: BigInt): BigInt = if(i<2) 1 else i*fac(i-1)
fac: (i: BigInt)BigInt
scala> def facCached(i: BigInt): BigInt = cached { if(i < 2) 1 else i * facCached(i - 1) }
facCached: (i: BigInt)BigInt
scala> time { (1 to 10000).foreach(_ => fac(200)) }
471409 microseconds
scala> time { (1 to 10000).foreach(_ => facCached(200)) }
14720 microseconds