This is a construct I come across quite a lot. Is there a nice way to one-line it in Swift? I could just write an extension on Sequence for it, but I feel like there's a "obvious" higher-order-fun...

I am a bit confused about the name Intersection Types in Typescript. In set theory, intersection would imply that only properties that are common to both types would be available in the intersectio...

The above shaded area, according to Wolfram is supposed to represent: A XOR B XOR C XOR (A AND B AND C) How to translate this into python code? The code must closely correlate to the set ope...

I have two collections a and b. I would like to compute the set of items in either a or b, but not in both (a logical exclusive or). With LINQ, I can come up with this: IEnumerable<T> Delta&...

I'm trying to determine how many different ways I can remove a group of values from a sequence, leaving the original sequence in order (stable), and making sure to remove only 1 instance value each...

How can I describe in Coq that one set Y is a subset of another set X? I tested the following: Definition subset (Y X:Set) : Prop := forall y:Y, y:X. , trying to express that if an element y i...

I have two NSArrays A and B that share some common elements, e.g. A: 1,2,3,4,5 B: 4,5,6,7 I would like to create a new NSArray consisting of the contents common between the two NSArrays joined ...

Given the input array [a,b,c,d,e] and a 'join' function (a,b) => (a+b) my code returns the following array of arrays, containing each possible variation obtained by applying the join functio...

I've had trouble understanding joins in sql and came upon this image which I think might help me. The problem is that I don't fully understand it. For example, the join in the top right corner of t...

I am trying to implement a list difference routine in prolog. For some reason the following fails: difference(Xs,Ys,D) :- difference(Xs,Ys,[],D). difference([],_,A,D) :- D is A, !. difference([X|X...

I'm designing a class library for discrete mathematics, and I can't think of a way to implement an infinite set. What I have so far is: I have an abstract base class, Set, which implements the int...

Assuming that you want to implement set theory concepts such as element, set, collection and relation in Java: How would you represent the empty set ∅? Do I mislead myself, if I think of the...

Assume we have trillions of sets stored somewhere. The domain for each of these sets is the same. It is also finite and discrete. So each set may be stored as a bit field (eg: 0000100111...) of a r...

How to implement set theory operations in pure php?

Recently I came across a situation where set theory and set math fit what I was doing to the letter (granted there was an easier way to accomplish what I needed - i.e. LINQ - but I didn't think of ...

I'm drawing a blank, or as some would say, having a senior moment. I know there’s a formal definition and a name for the concept where a db operation (stored procedure) that runs in a database will...