Add FuzzyRule and custom operator

Author: yalishanda42

Sources/FuzzyLogic/BinaryFuzzyRelation+implication.swift

@@ -8,7 +8,17 @@ public extension BinaryFuzzyRelation {
         method: ImplicationMethod = .mamdani
     ) -> Self where P.Universe == U, Q.Universe == V {
         .init {
-            method.function(antecedent[$0.0], consequent[$0.1])
+            (antecedent --> consequent)
+                .apply($0.0, $0.1, method: method)
+        }
+    }
+    
+    static func implication<P: FuzzySet, Q: FuzzySet>(
+        rule: FuzzyRule<P, Q>,
+        method: ImplicationMethod = .mamdani
+    ) -> Self where P.Universe == U, Q.Universe == V {
+        .init {
+            rule.apply($0.0, $0.1, method: method)
         }
     }
 }

Sources/FuzzyLogic/FuzzyRule.swift

@@ -0,0 +1,24 @@
+import FuzzySets
+
+public struct FuzzyRule<P: FuzzySet, Q: FuzzySet> {
+    public let antecedent: P
+    public let consequent: Q
+    
+    public init(antecedent: P, consequent: Q) {
+        self.antecedent = antecedent
+        self.consequent = consequent
+    }
+    
+    public func apply(
+        _ p: P.Universe,
+        _ q: Q.Universe,
+        method: ImplicationMethod = .mamdani
+    ) -> Grade {
+        method.function(antecedent[p], consequent[q])
+    }
+}
+
+infix operator -->: TernaryPrecedence  // lower than ==, &&, ||, etc
+public func --> <P: FuzzySet, Q: FuzzySet> (lhs: P, rhs: Q) -> FuzzyRule<P, Q> {
+    .init(antecedent: lhs, consequent: rhs)
+}

Sources/FuzzyLogic/FuzzySetComposition+generalizedModusPonens.swift

@@ -0,0 +1,18 @@
+import FuzzySets
+import FuzzyRelations
+
+public extension FuzzySetComposition {
+    static func generalizedModusPonens<P: FuzzySet, Q: FuzzySet>(
+        premise: FuzzyRule<P, Q>,
+        fact: IterableFuzzySet<U, Seq>,
+        method: ImplicationMethod = .mamdani
+    ) -> Self where P.Universe == U, Q.Universe == V {
+         .init(
+            set: fact,
+            relation: .implication(
+                rule: premise,
+                method: method
+            )
+        )
+    }
+}