lean2/tests/lean/acc.lean

import logic.prop

inductive acc (A : Type) (R : A → A → Prop) :  A → Prop :=
intro : ∀ (x : A), (∀ (y : A), R y x → acc A R y) → acc A R x

check @acc.rec
feat(library/logic): import wf.lean in logic/default.lean We will use well-founded recursion in the definitional package 2014-11-06 23:03:13 +00:00			`import logic.prop`
feat(kernel/inductive): relax conditions for an inductive datatype in Prop to be able to eliminate into Type The new relaxed version allows us to define the "accessability" proposition and have an eliminator into Type. See justification in the new comments at inductive.cpp 2014-11-06 17:36:54 +00:00
			`inductive acc (A : Type) (R : A → A → Prop) : A → Prop :=`
			`intro : ∀ (x : A), (∀ (y : A), R y x → acc A R y) → acc A R x`

			`check @acc.rec`