lean2/tests/lean/run/eq5.lean

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Text

open nat
definition fib : nat → nat
| fib 0 := 1
| fib 1 := 1
| fib (x+2) := fib x + fib (x+1)
theorem fib0 : fib 0 = 1 :=
rfl
theorem fib1 : fib 1 = 1 :=
rfl
theorem fib_succ_succ (a : nat) : fib (a+2) = fib a + fib (a+1) :=
rfl
example : fib 8 = 34 :=
rfl