slice exercise

go/01-basics/slice.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func main() {
+	//create an array with a lot of data
+	massiveData := make([]int, 1_000_000)
+	for i := range massiveData {
+		massiveData[i] = i
+	}
+
+	// Task: Extract the first 8 elements safely
+
+	//1. attempt: use the slice operator
+	//smallSlice := massiveData[:8]
+	// consequence -> smallSlice and massiveData point to the same underlying array.
+	// Therefore, setting massiveData to nil is not sufficient to release that big array.
+
+	//2. attempt: create a new slice (with a new underlying array) and copy data
+	smallSlice := make([]int, 8)
+	copy(smallSlice, massiveData[:8])
+
+	massiveData = nil //don't use massive data anymore: Underlying array shall be freed.
+	runtime.GC()      //run the garbage collector to make sure that all unused data is actually freed
+
+	//cap(smallSlice) should be 8 or similar, but not close to 1_000_000. The majority of the data should have been released by now
+	fmt.Printf("Small Slice: %v, Len: %d, Cap: %d\n", smallSlice, len(smallSlice), cap(smallSlice))
+}