First commit

Naturals.agda

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+{-# OPTIONS --safe --warning=error --without-K #-}
+
+module Naturals where
+
+data ℕ : Set where
+  zero : ℕ
+  succ : ℕ → ℕ
+
+{-# BUILTIN NATURAL ℕ #-}
+
+_+N_ : ℕ → ℕ → ℕ
+zero +N b = b
+succ a +N b = succ (a +N b)