deque

A double-ended queue for Ecko: push/pop/peek at both ends, amortized O(1). Immutable two-stack deque. Pure - no capabilities.

ecko get github.com/ecko-lang/deque

import deque

Pure computation: it declares no capabilities, so it cannot touch the network, the filesystem or the environment.

Version 0.9.5 - source - MIT.

`new()`

new() -> an empty deque. Deques are values, so every operation returns a new one rather than mutating.

size(q) -> item count.

is_empty(q) -> true when size is 0.

push_front(q, x) -> a new deque with x at the front.

q = push_front(new(), 1)

push_back(q, x) -> a new deque with x at the back.

peek_front(q) -> the front item, or null if empty. Does not remove it.

peek_back(q) -> the back item, or null if empty. Does not remove it.

pop_front(q) -> [front, new_deque]. Raises kind-"value" if empty.

pop_back(q) -> [back, new_deque]. Raises kind-"value" if empty.

to_list(q) -> the items as a plain list, front to back.

from_list(l) -> a deque holding l, front to back. Inverse of to_list.