example C extension

Author: johnno1962

README.md

@@ -0,0 +1,4 @@
+
+### Example C extension
+
+Revised from [Ben Snider's tutorial](https://www.bensnider.com/wrapping-c-code-within-a-single-swift-package.html)

Sources/Clibadder/Clibadder.swift

@@ -1,24 +1,27 @@
 import libadder
-protocol Addable {
+public protocol Addable {
     func add(_ x: Int, _ y: Int) -> Int
 }
 
 public struct SimpleAdd: Addable {
-    func add(_ x: Int, _ y: Int) -> Int {
+    public init() {}
+    public func add(_ x: Int, _ y: Int) -> Int {
         return libadder.add(x, y)
     }
 }
 
 public struct StructAdd: Addable {
-    func add(_ x: Int, _ y: Int) -> Int {
+    public init() {}
+    public func add(_ x: Int, _ y: Int) -> Int {
         let op = add_operation(x: x, y: y, result: 0)
         let result = libadder.added(op)
         return result.result;
     }
 }
 
 public struct PointerAdd: Addable {
-    func add(_ x: Int, _ y: Int) -> Int {
+    public init() {}
+    public func add(_ x: Int, _ y: Int) -> Int {
         var op = add_operation(x: x, y: y, result: 0)
         libadder.adding(&op)
         return op.result;