add: slice internals exercises

16-slices/exercises/20-observe-the-cap-growth/main.go

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+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Observe the capacity growth
+//
+//  Write a program that loops 10 million times to append an element
+//  to a slice, on each step of the loop. Observe the capacity.
+//
+//
+// STEPS
+//
+//  1. Create a nil slice
+//
+//  2. Loop 10e6 times
+//
+//  3. On each loop step: Append an element to the slice
+//
+//  4. Only print the length and capacity of the slice everytime
+//     the capacity changes.
+//
+//  5. Print also the growth rate by calculating the previous and
+//     the current capacity.
+//
+//
+// EXPECTED OUTPUT
+//
+//  len:0               cap:0               growth:NaN
+//  len:1               cap:1               growth:+Inf
+//  len:2               cap:2               growth:2.00
+//  ... and so on.
+//
+// ---------------------------------------------------------
+
+func main() {}

16-slices/exercises/20-observe-the-cap-growth/solution/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "fmt"
+
+func main() {
+	var (
+		nums   []int
+		oldCap float64
+	)
+
+	for len(nums) < 10e6 {
+		c := float64(cap(nums))
+
+		if c == 0 || c != oldCap {
+			fmt.Printf("len:%-15d cap:%-15g growth:%-15.2f\n",
+				len(nums), c, c/oldCap)
+		}
+		oldCap = c
+
+		nums = append(nums, 1)
+	}
+}