19 lines
450 B
Text
19 lines
450 B
Text
exit
|
|
import data.nat
|
|
open nat
|
|
|
|
structure less_than (n : nat) := (val : nat) (lt : val < n)
|
|
|
|
namespace less_than
|
|
open decidable
|
|
|
|
set_option pp.beta false
|
|
|
|
definition less_than.has_decidable_eq [instance] (n : nat) : ∀ (i j : less_than n), decidable (i = j)
|
|
| (mk ival ilt) (mk jval jlt) :=
|
|
match nat.has_decidable_eq ival jval with
|
|
| inl veq := inl (by subst veq)
|
|
| inr vne := inr (by intro h; injection h; contradiction)
|
|
end
|
|
|
|
end less_than
|