Comments on: STL Algorithms on Sets https://www.fluentcpp.com/2017/12/29/stl-algorithms-sets/ Jonathan Boccara's blog Sun, 21 Jan 2018 22:32:00 +0000 hourly 1 https://wordpress.org/?v=6.5.3 By: Jonathan Boccara https://www.fluentcpp.com/2017/12/29/stl-algorithms-sets/#comment-767 Sun, 21 Jan 2018 22:32:00 +0000 https://www.fluentcpp.com/?p=2830#comment-767 In reply to Joep Lijnen.

If I reformulate to make sure I get everything you said: the fact that sets are sorted is an implementation technique to ensure the uniqueness of their elements, which is their prominent feature coming from maths.
And the fact they are sorted also allows implementing mathematical operations on sets conveniently. Did I get this right?
Thanks for exposing this Joep, I never thought of it that way. But it makes a lot of sense.
And I’m wondering then, do you think that a “multiset” an occimoron then?

]]> By: Joep Lijnen https://www.fluentcpp.com/2017/12/29/stl-algorithms-sets/#comment-755 Tue, 16 Jan 2018 10:35:00 +0000 https://www.fluentcpp.com/?p=2830#comment-755 Please, please please please do not say that sets are ordered collections; this is an incorrect generalization of the definition of set. Not understanding this can lead to severe programming errors that only manifest at run-time.

The elements in a vector are ordered, they need not be unique.
The elements (indices) in a hash-map are unique, they are not ordered.

What happens when we have programmers that do not understand the difference between a set and an ordered list? – I would hate to clean up after such a mess.

> In mathematics, a set is a collection of distinct objects, considered as an object in its own right.
>Moreover, the order in which the elements of a set are listed is irrelevant

Wikipedia](https://en.wikipedia.org/wiki/Set_(mathematics)

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