Just another update

Task/Fibonacci-sequence/ATS/fibonacci-sequence-4.ats

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+(* ****** ****** *)
+//
+// How to compile:
+// patscc -o fib fib.dats
+//
+(* ****** ****** *)
+//
+#include
+"share/atspre_staload.hats"
+//
+(* ****** ****** *)
+//
+abst@ype
+int3_t0ype =
+  (int, int, int)
+//
+typedef int3 = int3_t0ype
+//
+(* ****** ****** *)
+
+extern
+fun int3 : (int, int, int) -<> int3
+extern
+fun int3_1 : int3 -<> int
+extern
+fun mul_int3_int3: (int3, int3) -<> int3
+
+(* ****** ****** *)
+
+local
+
+assume
+int3_t0ype = (int, int, int)
+
+in (* in-of-local *)
+//
+implement
+int3 (x, y, z) = @(x, y, z)
+//
+implement int3_1 (xyz) = xyz.1
+//
+implement
+mul_int3_int3
+(
+  @(a,b,c), @(d,e,f)
+) =
+  (a*d + b*e, a*e + b*f, b*e + c*f)
+//
+end // end of [local]
+
+(* ****** ****** *)
+//
+implement
+gnumber_int<int3> (n) = int3(n, 0, n)
+//
+implement gmul_val<int3> = mul_int3_int3
+//
+(* ****** ****** *)
+//
+fun
+fib (n: intGte(0)): int =
+  int3_1(gpow_int_val<int3> (n, int3(1, 1, 0)))
+//
+(* ****** ****** *)
+
+implement
+main0 () =
+{
+//
+val N = 10
+val () = println! ("fib(", N, ") = ", fib(N))
+val N = 20
+val () = println! ("fib(", N, ") = ", fib(N))
+val N = 30
+val () = println! ("fib(", N, ") = ", fib(N))
+val N = 40
+val () = println! ("fib(", N, ") = ", fib(N))
+//
+} (* end of [main0] *)