lean2/tests/lean/run/eq22.lean

import data.list
open list

definition head {A : Type} : Π (l : list A), l ≠ nil → A
| head nil h      := absurd rfl h
| head (a :: l) _ := a

theorem head_cons {A : Type} (a : A) (l : list A) (h : a :: l ≠ nil) : head (a :: l) h = a :=
rfl
test(tests/lean/run): define list head using recursive equations 2015-01-06 03:50:07 +00:00			`import data.list`
			`open list`

feat(frontends/lean): ML-like notation for match and recursive equations 2015-02-26 00:20:44 +00:00			`definition head {A : Type} : Π (l : list A), l ≠ nil → A`
			`\| head nil h := absurd rfl h`
			`\| head (a :: l) _ := a`
test(tests/lean/run): define list head using recursive equations 2015-01-06 03:50:07 +00:00
			`theorem head_cons {A : Type} (a : A) (l : list A) (h : a :: l ≠ nil) : head (a :: l) h = a :=`
			`rfl`