[Haskell-cafe] [ANN] compact-sequences-

☂Josh Chia (謝任中) joshchia at gmail.com
Wed Sep 2 04:26:04 UTC 2020

Isn't a stack O(1) time for push & pop and O(n) space? What is the tradeoff
being made here, where both space and time complexity increased?

Or, am I missing something about the meaning of "n + O(log)", where the 'n'
is not inside an 'O'. I don't really know what "n + O(log)" means exactly.

On Wed, Sep 2, 2020 at 12:21 PM David Feuer <david.feuer at gmail.com> wrote:

> Typical stacks, queues, and deques are designed to have O(1) operations.
> These ones experiment in a different direction.
> On Wed, Sep 2, 2020, 12:19 AM ☂Josh Chia (謝任中) <joshchia at gmail.com> wrote:
>> Could you elaborate on what the package does? The description is "Stacks,
>> queues, and deques that take n + O(log n) space at the cost of having
>> amortized O(log n) time complexity for basic operations." But why is it a
>> 'cost' to have O(log n) instead of O(n) cost for basic operations on
>> list-like structures (such as insert and delete presumably)? So, I didn't
>> understand what the package is for.
>> Do you mean "take amortized O(log n) time for basic operations at the
>> cost of n + O(log n) space"? Or is it something else I didn't imagine?
>> On Wed, Sep 2, 2020 at 4:17 AM David Feuer <david.feuer at gmail.com> wrote:
>>> I am pleased to release the second version of the compact-sequences
>>> package, now with deques!
>>> Changes:
>>> * Add deques.
>>> * Change operator precedence.
>>> * Add a test suite. Thanks to David Himmelstrup for setting up the
>>> test and CI framework.
>>> * Clean up internals somewhat.
>>> * Add a proof of amortized bounds for the stack implementation.
>>> Thanks, Li-Yao Xia.
>>> There are still plenty of things to work on, and help is always welcome.
>>> David Feuer
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