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CreatedFebruary 19, 2009 13:51
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Scala-Metaprogramming: Towers of Hanoi
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| /* | |
| * This is the Towers of Hanoi example from the prolog tutorial [1] | |
| * converted into Scala, using implicits to unfold the algorithm at | |
| * compile-time. | |
| * | |
| * [1] http://www.csupomona.edu/~jrfisher/www/prolog_tutorial/2_3.html | |
| */ | |
| objectTowersOfHanoi { | |
| importscala.reflect.Manifest | |
| defsimpleName(m:Manifest[_]):String= { | |
| valname= m.toString | |
| name.substring(name.lastIndexOf('$')+1) | |
| } | |
| traitNat | |
| finalclass_0extendsNat | |
| finalclassSucc[Pre<:Nat]extendsNat | |
| type_1=Succ[_0] | |
| type_2=Succ[_1] | |
| type_3=Succ[_2] | |
| type_4=Succ[_3] | |
| caseclassMove[N<:Nat,A,B,C]() | |
| implicitdefmove0[A,B,C](implicit a:Manifest[A],b:Manifest[B]):Move[_0,A,B,C]= { | |
| System.out.println("Move from"+simpleName(a)+" to"+simpleName(b));null | |
| } | |
| implicitdefmoveN[P<:Nat,A,B,C](implicit m1:Move[P,A,C,B],m2:Move[_0,A,B,C],m3:Move[P,C,B,A]) | |
| :Move[Succ[P],A,B,C]=null | |
| defrun[N<:Nat,A,B,C](implicit m:Move[N,A,B,C])=null | |
| caseclassLeft() | |
| caseclassCenter() | |
| caseclassRight() | |
| defmain(args:Array[String]){ | |
| run[_2,Left,Right,Center] | |
| } | |
| } |
Using shapeless I created a version which moves the result to the type.
It obviously ruins the 'self-contained'ness of the gist, but here it is:https://gist.github.com/HusrevAtSky/cae020c79c844e22024c8cd027a5c6ce
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