added basic info about Swift Sets (#30395)

guide/english/swift/sets/index.md

@@ -0,0 +1,90 @@
+---
+title: Sets
+---
+
+# Sets 
+
+Sets are a collection type that stores an **unordered list** of **distinct** values of a given type. They are useful when the order of your elements do not matter, and also when you want to ensure that an element only occurs once.
+
+### Initialization
+
+Creating an empty Set...
+```swift
+var integerSet = Set<Int>()
+```
+
+Using Arrays to Create Sets...
+```swift
+let posSet: Set<Int> = [0,1,2,3,4,5]
+let negSet: Set = [-1,-2,-3,-4,-5]
+```
+
+### Set Modification
+
+Insert and Remove an element from a set.
+
+```swift
+integerSet.insert(10312018) //insert the integer "10312018" into the set
+integerSet.remove(10312018) //remove the integer "10312018" from the set
+```
+
+### Set Operations
+
+There are four fundamental set operations that can be performed on sets: union, intersection, subtraction, and symmetric difference 
+
+_Note_: The **sorted()** method used in the proceeding code, returns an array of the the elements of the set sorted in ascending order. It is primarily used in the below code for clarity.
+
+**_Union_:** combines the elements of two sets
+
+```swift
+integerSet = integerSet.union(posSet) // performs a union operation that returns a new set
+integerSet.formUnion(negSet) // performs a union operation that modifies the current set
+
+integerSet.sorted() // [-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
+```
+
+**_Intersection_:** forms a set from only the common values of two sets
+
+```swift
+let oddSet: Set = [1,3,5,9]
+let _ = integerSet.intersection(oddSet).sorted(); // [1,3,5]
+```
+
+**_Symmetric Difference_:** forms a set from the values that are not common in both sets.
+```swift
+let inbetweenSet: Set<Int> = [-4,-3,-2,-1,0,1,2,3,4]
+let _ = integerSet.symmetricDifference(inbetweenSet).sorted() // [-5,5]
+```
+
+**_Subtraction_:** : forms a set with values not in the specified set.
+```swift
+integerSet.subtract(negSet)
+integerSet.sorted() // [0, 1, 2, 3, 4, 5]
+```
+
+### Iterating Over a Set
+
+You can iterate over a set by using a for-in loop...
+```swift
+var showSet = "";
+for item in integerSet {
+    showSet += "\(item) "
+}
+print(showSet) 
+```
+The output for the above code is going to be along the lines of "1 5 4 3 0 2"... which of course is not in order. To iterate over a set in an orderly fashion use the sorted() method...
+
+```swift
+showSet = "";
+for item in integerSet.sorted() {
+    showSet += "\(item) "
+}
+print(showSet)
+```
+Output: "0 1 2 3 4 5" 
+
+
+#### More Information:
+
+* [The Swift Programming Language](https://docs.swift.org/swift-book/LanguageGuide/CollectionTypes.html#ID484)
+