2 files changed, 40 insertions, 0 deletions
diff --git a/entries/ionathanch/Fib.agda b/entries/ionathanch/Fib.agda
new file mode 100644
index 0000000..a12b0a5
--- /dev/null
+++ b/entries/ionathanch/Fib.agda
@@ -0,0 +1,19 @@
+
+open import Agda.Builtin.Nat
+open import Agda.Builtin.List
+open import Agda.Builtin.Reflection
+
+data Fib : Nat → Nat → Set where
+  instance F0 : Fib 0 0
+  instance F1 : Fib 1 1
+  instance Fk : ∀ {k n m} → ⦃ Fib k n ⦄ → ⦃ Fib (suc k) m ⦄ → Fib (suc (suc k)) (n + m)
+
+fib' : ∀ k {n} → ⦃ Fib k n ⦄ → Nat
+fib' k {n} ⦃ fib ⦄ = n
+
+macro
+  fib : Term → Term → TC _
+  fib t hole = unify hole (def (quote fib') (arg i t ∷ []))
+    where i = arg-info visible (modality relevant quantity-ω)
+
+{- Get the [n]th Fibonacci number by normalization via C-n `fib [n]`. -}
diff --git a/entries/ionathanch/fib.f90 b/entries/ionathanch/fib.f90
new file mode 100644
index 0000000..3cf1850
--- /dev/null
+++ b/entries/ionathanch/fib.f90
@@ -0,0 +1,21 @@
+PROGRAM main
+  ! The 93rd Fibonacci number is the largest that fits in 64 bits anyway
+  CHARACTER(3) :: kth
+  INTEGER :: k
+  CALL get_command_argument(1, kth)
+  READ(kth, *) k
+  WRITE(*, *) fib(k)
+CONTAINS
+
+PURE RECURSIVE INTEGER*8 FUNCTION fib(k) RESULT(n)
+  INTEGER, INTENT (IN) :: k
+  IF (k == 0) THEN
+    n = 0
+  ELSE IF (k == 1) THEN
+    n = 1
+  ELSE
+    n = fib(k - 1) + fib(k - 2)
+  END IF
+END FUNCTION fib
+
+END PROGRAM