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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.javascript
Subject: Re: passing a set of numbers to a function
Date: Fri, 05 Feb 2016 13:43:57 +0000
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Scott Sauyet <scott.sauyet@gmail.com> writes:

> I (Scott Sauyet) wrote:
>> There is a simple way to implement mathematical sets, finite or 
>> infinite using predicate functions.  [ ... ]
>> 
>>     const set = pred => ({
>>       contains: pred,
>>       union: set2 => set(val => pred(val) || set2.contains(val)),
>>       intersection: set2 => set(val => pred(val) && set2.contains(val)),
>>       complement: () => set(val => !pred(val))
>>     });
>>
>> [ ... ] But, for one trying to use a set as a Collection, these 
>> are missing several important features.  Obviously there is no way 
>> to add or remove members. [ ... ]
>
> This was perhaps hasty.  Of course sets defined this way are 
> immutable, and hence one cannot add or remove members, but just as
> we can create new sets from old in `union`, we can easily derive
> new sets with `add` and `remove` functions:

They can be made mutable by storing a predicate.  Then they would like
the mutable sets that most people are familiar with.  But since I prefer
a function style (as do you I think) I would not bother.

<snip>
-- 
Ben.