pointers

about_pointers.go

@@ -0,0 +1,40 @@
+package go_koans
+
+func testPointers() {
+  {
+    a := 3
+    b := a // 'b' is a copy of 'a' (all assignments are copy-operations)
+
+    b++
+
+    assert(a == __int__) // variables are independent of one another
+  }
+
+  {
+    a := 3
+    b := &a // 'b' is the address of 'a'
+
+    *b = *b + 2 // de-referencing 'b' means acting like a mutable copy of 'a'
+    assert(a == __int__) // pointers seem complicated at first but are actually simple
+  }
+
+  {
+    increment := func(i int) {
+      i++
+    }
+
+    a := 3
+    increment(a)
+    assert(a == __int__) // variables are always passed by value, and so a copy is made
+  }
+
+  {
+    realIncrement := func(i *int) {
+      (*i)++
+    }
+
+    b := 3
+    realIncrement(&b)
+    assert(b == __int__) // but passing a pointer allows others to mutate the value pointed to
+  }
+}

setup_koans_test.go

@@ -27,12 +27,12 @@ func TestKoans(t *testing.T) {
   //testVariadicFunctions()
   //testFiles()
   //testInterfaces()
-  testMaps()
+  //testMaps()
+  testPointers()
 
   // TODO: ie, gameplan
   //testStructs()
   //testAllocation()
-  //testPointers()
   //testGoroutines()
   //testChannels()
   //testPanics()