diff options
Diffstat (limited to 'theories/Init/Nat.v')
| -rw-r--r-- | theories/Init/Nat.v | 68 |
1 files changed, 63 insertions, 5 deletions
diff --git a/theories/Init/Nat.v b/theories/Init/Nat.v index b8920586..ad1bc717 100644 --- a/theories/Init/Nat.v +++ b/theories/Init/Nat.v @@ -1,13 +1,15 @@ (************************************************************************) -(* v * The Coq Proof Assistant / The Coq Development Team *) -(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016 *) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2018 *) +(* <O___,, * (see CREDITS file for the list of authors) *) (* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) (************************************************************************) Require Import Notations Logic Datatypes. - +Require Decimal. Local Open Scope nat_scope. (**********************************************************************) @@ -134,6 +136,62 @@ Fixpoint pow n m := where "n ^ m" := (pow n m) : nat_scope. +(** ** Tail-recursive versions of [add] and [mul] *) + +Fixpoint tail_add n m := + match n with + | O => m + | S n => tail_add n (S m) + end. + +(** [tail_addmul r n m] is [r + n * m]. *) + +Fixpoint tail_addmul r n m := + match n with + | O => r + | S n => tail_addmul (tail_add m r) n m + end. + +Definition tail_mul n m := tail_addmul 0 n m. + +(** ** Conversion with a decimal representation for printing/parsing *) + +Local Notation ten := (S (S (S (S (S (S (S (S (S (S O)))))))))). + +Fixpoint of_uint_acc (d:Decimal.uint)(acc:nat) := + match d with + | Decimal.Nil => acc + | Decimal.D0 d => of_uint_acc d (tail_mul ten acc) + | Decimal.D1 d => of_uint_acc d (S (tail_mul ten acc)) + | Decimal.D2 d => of_uint_acc d (S (S (tail_mul ten acc))) + | Decimal.D3 d => of_uint_acc d (S (S (S (tail_mul ten acc)))) + | Decimal.D4 d => of_uint_acc d (S (S (S (S (tail_mul ten acc))))) + | Decimal.D5 d => of_uint_acc d (S (S (S (S (S (tail_mul ten acc)))))) + | Decimal.D6 d => of_uint_acc d (S (S (S (S (S (S (tail_mul ten acc))))))) + | Decimal.D7 d => of_uint_acc d (S (S (S (S (S (S (S (tail_mul ten acc)))))))) + | Decimal.D8 d => of_uint_acc d (S (S (S (S (S (S (S (S (tail_mul ten acc))))))))) + | Decimal.D9 d => of_uint_acc d (S (S (S (S (S (S (S (S (S (tail_mul ten acc)))))))))) + end. + +Definition of_uint (d:Decimal.uint) := of_uint_acc d O. + +Fixpoint to_little_uint n acc := + match n with + | O => acc + | S n => to_little_uint n (Decimal.Little.succ acc) + end. + +Definition to_uint n := + Decimal.rev (to_little_uint n Decimal.zero). + +Definition of_int (d:Decimal.int) : option nat := + match Decimal.norm d with + | Decimal.Pos u => Some (of_uint u) + | _ => None + end. + +Definition to_int n := Decimal.Pos (to_uint n). + (** ** Euclidean division *) (** This division is linear and tail-recursive. |