dfd2a23cd4
The new notation is the same one used in Standard ML. It will also allow us to use ' in the beginning of identifiers like Standard ML.
31 lines
725 B
Text
31 lines
725 B
Text
/-
|
|
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
|
|
Released under Apache 2.0 license as described in the file LICENSE.
|
|
Author: Leonardo de Moura
|
|
-/
|
|
prelude
|
|
import init.fin
|
|
|
|
open nat
|
|
def char_sz : nat := succ 255
|
|
|
|
def char := fin char_sz
|
|
|
|
namespace char
|
|
/- We cannot use tactic dec_trivial here because the tactic framework has not been defined yet. -/
|
|
private lemma zero_lt_char_sz : 0 < char_sz :=
|
|
zero_lt_succ _
|
|
|
|
@[pattern] def of_nat (n : nat) : char :=
|
|
if H : n < char_sz then fin.mk n H else fin.mk 0 zero_lt_char_sz
|
|
|
|
def to_nat (c : char) : nat :=
|
|
fin.val c
|
|
end char
|
|
|
|
instance : decidable_eq char :=
|
|
have decidable_eq (fin char_sz), from fin.decidable_eq _,
|
|
this
|
|
|
|
instance : inhabited char :=
|
|
⟨#"A"⟩
|