2021-12-01 16:24:29 +00:00
|
|
|
/// SPDX-License-Identifier: GPL-3.0-or-later
|
2023-01-17 10:43:15 +00:00
|
|
|
/// SPDX-FileCopyrightText: Copyright © 2016-2023 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
|
2018-11-01 14:55:45 +00:00
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export type NonEmptyStack<T> = { item: T, rest: Stack<T> };
|
|
|
|
export type Stack<T> = null | NonEmptyStack<T>;
|
2018-10-22 14:29:07 +00:00
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function empty<T>(): Stack<T> {
|
|
|
|
return null;
|
|
|
|
}
|
2019-06-14 14:33:02 +00:00
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function push<T>(item: T, rest: Stack<T>): NonEmptyStack<T> {
|
|
|
|
return { item, rest };
|
|
|
|
}
|
2018-10-22 14:29:07 +00:00
|
|
|
|
2021-01-15 12:38:15 +00:00
|
|
|
export function isEmpty<T>(s: Stack<T>): s is null {
|
|
|
|
return s === null;
|
|
|
|
}
|
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function nonEmpty<T>(s: Stack<T>): s is NonEmptyStack<T> {
|
2021-01-15 12:38:15 +00:00
|
|
|
return s !== null;
|
2018-10-22 14:29:07 +00:00
|
|
|
}
|
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function rest<T>(s: Stack<T>): Stack<T> {
|
|
|
|
if (nonEmpty(s)) {
|
|
|
|
return s.rest;
|
2018-10-22 14:29:07 +00:00
|
|
|
} else {
|
2021-01-11 22:35:36 +00:00
|
|
|
throw new Error("pop from empty Stack");
|
2018-10-22 14:29:07 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function drop<T>(s: Stack<T>, n: number): Stack<T> {
|
|
|
|
while (n--) s = rest(s);
|
|
|
|
return s;
|
|
|
|
}
|
2018-10-22 14:29:07 +00:00
|
|
|
|
2021-01-11 22:35:36 +00:00
|
|
|
export function dropNonEmpty<T>(s: NonEmptyStack<T>, n: number): NonEmptyStack<T> {
|
|
|
|
while (n--) {
|
2021-01-15 12:38:15 +00:00
|
|
|
const next = s.rest;
|
|
|
|
if (!nonEmpty(next)) throw new Error("dropNonEmpty popped too far");
|
|
|
|
s = next;
|
2021-01-11 22:35:36 +00:00
|
|
|
}
|
|
|
|
return s;
|
|
|
|
}
|
2021-12-09 17:47:43 +00:00
|
|
|
|
|
|
|
export function depth<T>(s: Stack<T>): number {
|
|
|
|
let count = 0;
|
|
|
|
while (s !== null) {
|
|
|
|
count++;
|
|
|
|
s = s.rest;
|
|
|
|
}
|
|
|
|
return count;
|
|
|
|
}
|
|
|
|
|
|
|
|
export function toArray<T>(s: Stack<T>): T[] {
|
|
|
|
const result = [];
|
|
|
|
while (s !== null) {
|
|
|
|
result.push(s.item);
|
|
|
|
s = s.rest;
|
|
|
|
}
|
|
|
|
return result;
|
|
|
|
}
|