Add nqueens benchmark (new kraken impl, with koka and cpp moved over from koka_bench)

koka_bench/koka/CMakeLists.txt

@@ -1,4 +1,4 @@
-set(sources rbtree.kk)
+set(sources rbtree.kk nqueens.kk nqueens-int.kk)
 
 set(koka koka)
 

koka_bench/koka/nqueens-int.kk

@@ -0,0 +1,31 @@
+module nqueens-int
+import std/os/env
+
+alias solution = list<int>
+alias solutions = list<list<int>>
+
+fun safe( queen : int, diag : int, ^xs : solution ) : bool
+  match xs
+    Cons(q,qs) -> (queen != q && queen != q + diag && queen != q - diag && safe(queen,diag + 1,qs))
+    _          -> True
+
+fun append-safe( queen : int, xs : solution, xss : solutions ) : div solutions
+  if queen <= 0 then xss
+  elif safe(queen,1,xs) then append-safe( queen - 1, xs, Cons(Cons(queen,xs),xss) )
+  else append-safe( queen - 1, xs, xss )
+
+fun extend(queen : int, acc : solutions, xss : solutions ) : div solutions
+  match xss
+    Cons(xs,rest) -> extend(queen, append-safe(queen,xs,acc), rest)
+    Nil           -> acc
+
+fun find-solutions( n : int, queen : int ) : div solutions
+  if queen == 0
+   then [[]]
+   else extend(n,[], find-solutions(n,queen - 1))
+
+pub fun queens( n : int ) : div int
+  find-solutions(n,n).length
+
+pub fun main()
+  queens(get-args().head("").parse-int.default(13)).println

koka_bench/koka/nqueens.kk

@@ -0,0 +1,32 @@
+module nqueens
+import std/num/int32
+import std/os/env
+
+alias solution = list<int32>
+alias solutions = list<list<int32>>
+
+fun safe( queen : int32, diag : int32, ^xs : solution ) : bool 
+  match xs
+    Cons(q,qs) -> (queen != q && queen != (q+diag) && queen != (q - diag) && safe(queen,diag.inc,qs))
+    _          -> True
+
+fun append-safe( queen : int32, xs : solution, xss : solutions ) : div solutions 
+  if queen <= 0.int32 then xss
+  elif safe(queen,1.int32,xs) then append-safe( queen.dec, xs, Cons(Cons(queen,xs),xss) )
+  else append-safe( queen.dec, xs, xss )
+
+fun extend( queen : int32, acc : solutions, xss : solutions ) : div solutions
+  match xss 
+    Cons(xs,rest) -> extend(queen, append-safe(queen,xs,acc), rest)
+    Nil           -> acc
+
+fun find-solutions( n : int32, queen : int32 ) : div solutions
+  if queen.is-zero
+   then [[]]
+   else extend(n, [], find-solutions(n,queen.dec))
+
+pub fun queens( n : int32 ) : div int
+  find-solutions(n,n).length
+
+pub fun main()
+  queens(get-args().head("").parse-int.default(13).int32).println