44 lines
1.8 KiB
TypeScript
44 lines
1.8 KiB
TypeScript
/**
|
|
* Numeric types
|
|
*
|
|
* Copyright (C) 2010-2019 R-T Specialty, LLC.
|
|
*
|
|
* This file is part of the Liza Data Collection Framework.
|
|
*
|
|
* liza is free software: you can redistribute it and/or modify
|
|
* it under the terms of the GNU Affero General Public License as
|
|
* published by the Free Software Foundation, either version 3 of the
|
|
* License, or (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Affero General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*
|
|
* TypeScript's type system does not support algebraic numeric domains. A
|
|
* compromise is to provide nominal types that allow developers to assume
|
|
* that some constraint has been met, and then ensure that the type is only
|
|
* ever asserted when that constraint is explicitly validated at
|
|
* runtime. This allows us to have compile-time checks on numeric values
|
|
* under the assumption that the runtime will enforce them.
|
|
*
|
|
* For this to work, _it is important to always use type predicates_;
|
|
* if you explicit cast to one of these numeric types, it circumvents the
|
|
* safety provided by the system and may introduce nasty bugs, since users
|
|
* of these types assume the provided data has already been validated.
|
|
*/
|
|
|
|
/**
|
|
* Any number ≥ 0
|
|
*
|
|
* This is useful for array indexing.
|
|
*/
|
|
export type PositiveInteger = NominalType<number, 'PositiveInteger'>;
|
|
|
|
|
|
/** Whether the given number is suitable as a PositiveInteger */
|
|
export const isPositiveInteger = ( n: number ): n is PositiveInteger => n >= 0;
|