Describe convertions in README and use Zadeh's notation

README.md

@@ -101,27 +101,35 @@ API Reference automatically collected with `jazzy` is published [here](https://a
 
 ## `FuzzySets` Module
 
-* `protocol FuzzySet`: This abstraction requires a fuzzy set to provide a `grade(forElement:)` method which accepts a parameter of an `associatedtype Universe` and returns its membership `Grade` in the set. There are 3 provided concrete implementations in this module:
-    1. `struct AnyFuzzySet` - allows type erasure. It only stores a `MembershipFunction` and has non-mutable methods.
-    2. `struct IterableFuzzySet` - stores a `MembershipFunction` as well as a `Sequence` of elements of the associated type `Universe`. Implements `Sequence` so that it can easily be iterated over them. The elements of the iteration over an `IterableFuzzySet` are `struct`s containing `grade` and `element` properties. It has non-mutable methods only.
-    3. `struct DiscreteMutableFuzzySet` - it is "discrete" because it doesn't stores a `MembershipFunction` but instead keeps its elements and their grade in a `Dictionary`, and it is "mutable" because it contains mutable equivalents of all other methods that operate over the set (including `subscript`). A default value of `0` is returned for the grade of an element that is not in the dictionary (a different default value can be provided as well).
+### `protocol FuzzySet`
+This abstraction requires a fuzzy set to provide a `grade(forElement:)` method which accepts a parameter of an `associatedtype Universe` and returns its membership `Grade` in the set. There are 3 provided concrete implementations in this module:
 
-* `protocol FuzzySetOperations` - all 3 concrete types implement it. It requires the following methods that operate on fuzzy sets:
-    * `alphaCut(_:alpha:)`
+1. `struct AnyFuzzySet` - allows type erasure. It only stores a `MembershipFunction` and has non-mutable methods.
 
-    * `complement(method:)`
+2. `struct IterableFuzzySet` - stores a `MembershipFunction` as well as a `Sequence` of elements of the associated type `Universe`. Implements `Sequence` so that it can easily be iterated over them. The elements of the iteration over an `IterableFuzzySet` are `struct`s containing `grade` and `element` properties. It has non-mutable methods only. Includes `support`, `core` and `height` computed properties.
 
-    * `intersection(_:method:)`
+3. `struct DiscreteMutableFuzzySet` - it is "discrete" because it doesn't stores a `MembershipFunction` but instead keeps its elements and their grade in a `Dictionary`, and it is "mutable" because it contains mutable equivalents of all other methods that operate over the set (including `subscript`). A default value of `0` is returned for the grade of an element that is not in the dictionary (a different default value can be provided as well). Includes `support`, `core` and `height` computed properties. A bonus feature is its debug print using Zadeh's notation.
 
-    * `union(_:method:)`
+Convertions between the 3 types are easy and possible using the `eraseToAnyFuzzySet`, `makeIterable` and `makeDiscreteMutable` methods defined on them.
 
-    * `difference(_:method:)`
+### `protocol FuzzySetOperations`
+All 3 concrete types implement it. It requires the following methods that operate on fuzzy sets:
 
-    * `symmetricDifference(_:method:)`
+* `alphaCut(_:alpha:)`
 
-    * `power(_:n:)`
+* `complement(method:)`
 
-    * `appliedCustomFunction(_:function:)`
+* `intersection(_:method:)`
+
+* `union(_:method:)`
+
+* `difference(_:method:)`
+
+* `symmetricDifference(_:method:)`
+
+* `power(_:n:)`
+
+* `appliedCustomFunction(_:function:)`
 
 ## License
 

Sources/FuzzySets/Implementations/DiscreteMutableFuzzySet.swift

@@ -19,7 +19,7 @@ public struct DiscreteMutableFuzzySet<Universe: Hashable>: ExpressibleByDictiona
 extension DiscreteMutableFuzzySet: FuzzySet {
     /// - Complexity: O(1)
     public func grade(forElement element: Universe) -> Grade {
-        grades[element] ?? defaultGrade
+        grades[element, default: defaultGrade]
     }
 }
 
@@ -120,6 +120,25 @@ public extension DiscreteMutableFuzzySet {
     mutating func applyPower(_ n: Double) {
         applyFunction { Double.pow($0, n) }
     }
+    
+    mutating func applyFunction(_ function: (Grade) -> Grade) {
+        let newGradeTuples = grades.map {
+            ($0.key, function($0.value))
+        }
+        let newMap = Dictionary(uniqueKeysWithValues: newGradeTuples)
+        grades = newMap
+        defaultGrade = function(defaultGrade)
+        sanitize()
+    }
+    
+    mutating func applyFunction(
+        _ function: (Grade, Grade) -> Grade,
+        whenMergingWith anotherSet: Self
+    ) {
+        grades.merge(anotherSet.grades, uniquingKeysWith: function)
+        defaultGrade = function(defaultGrade, anotherSet.defaultGrade)
+        sanitize()
+    }
 }
 
 // MARK: - Properties
@@ -169,36 +188,49 @@ public extension DiscreteMutableFuzzySet {
 // MARK: - Debug
 
 extension DiscreteMutableFuzzySet: CustomStringConvertible {
+    /// Pretty-print contents of `self` using Zadeh's notation.
     public var description: String {
         let guts = grades.map {
             "\($0.value)/\($0.key)"
-        }.joined(separator: ", ")
+        }.joined(separator: " + ")
         return "<FuzzySet: {\(guts)}, other values == \(defaultGrade)>"
     }
 }
 
+// MARK: - Convertion
+
+public extension AnyFuzzySet where Universe: Hashable {
+    func makeDiscreteMutable(
+        takeOnly set: Set<Universe>,
+        forOthersUse defaultValue: Grade = 0
+    ) -> DiscreteMutableFuzzySet<Universe> {
+        .init(
+            .init(uniqueKeysWithValues: set.map { ($0, self[$0]) }),
+            defaultGrade: defaultValue
+        )
+    }
+    
+    func makeDiscreteMutable<S: Sequence>(
+        takeOnly sequence: S,
+        forOthersUse defaultValue: Grade = 0
+    ) -> DiscreteMutableFuzzySet<Universe>
+    where S.Element == Universe {
+        .init(
+            .init(uniqueKeysWithValues: sequence.map { ($0, self[$0]) }),
+            defaultGrade: defaultValue
+        )
+    }
+}
+
+public extension IterableFuzzySet where Universe: Hashable {
+    func makeDiscreteMutable() -> DiscreteMutableFuzzySet<Universe> {
+        .init(.init(uniqueKeysWithValues: sequence.map { ($0, self[$0]) }))
+    }
+}
+
 // MARK: - Helpers
 
 extension DiscreteMutableFuzzySet {
-    public mutating func applyFunction(_ function: (Grade) -> Grade) {
-        let newGradeTuples = grades.map {
-            ($0.key, function($0.value))
-        }
-        let newMap = Dictionary(uniqueKeysWithValues: newGradeTuples)
-        grades = newMap
-        defaultGrade = function(defaultGrade)
-        sanitize()
-    }
-    
-    public mutating func applyFunction(
-        _ function: (Grade, Grade) -> Grade,
-        whenMergingWith anotherSet: Self
-    ) {
-        grades.merge(anotherSet.grades, uniquingKeysWith: function)
-        defaultGrade = function(defaultGrade, anotherSet.defaultGrade)
-        sanitize()
-    }
-    
     private mutating func sanitize() {
         grades = grades.filter {
             $0.value != defaultGrade

Sources/FuzzySets/Implementations/IterableFuzzySet.swift

@@ -142,12 +142,6 @@ public extension DiscreteMutableFuzzySet where Universe: CaseIterable {
     }
 }
 
-public extension IterableFuzzySet where Universe: Hashable {
-    func makeDiscreteMutable() -> DiscreteMutableFuzzySet<Universe> {
-        .init(.init(uniqueKeysWithValues: sequence.map { ($0, self[$0]) }))
-    }
-}
-
 // MARK: - Properties
 
 public extension IterableFuzzySet {

Tests/FuzzySetsTests/DiscreteMutableFuzzySetTests.swift

@@ -41,8 +41,8 @@ final class DiscreteMutableFuzzySetTests: XCTestCase {
             "b": 1,
         ]
         let sut = DiscreteMutableFuzzySet(parameters)
-        let expected1 = "<FuzzySet: {0.69/a, 1.0/b}, other values == 0.0>"
-        let expected2 = "<FuzzySet: {1.0/b, 0.69/a}, other values == 0.0>"
+        let expected1 = "<FuzzySet: {0.69/a + 1.0/b}, other values == 0.0>"
+        let expected2 = "<FuzzySet: {1.0/b + 0.69/a}, other values == 0.0>"
         
         let result = String(describing: sut)