learngo/16-slices/exercises/22-adv-ops-practice/solution/main.go

// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials  : https://learngoprogramming.com
// In-person training  : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus

package main

import (
	s "github.com/inancgumus/prettyslice"
)

func main() {
	// ########################################################
	//
	// #1: Create a string slice: `names` with a length and
	//     capacity of 5, and print it.
	//
	names := make([]string, 5)
	s.Show("1st step", names)

	// ########################################################
	//
	// #2: Append the following names to the names slice:
	//
	//     "einstein", "tesla", "aristotle"
	//
	//     Print the names slice.
	//
	//     Observe how the slice and its backing array change.
	//
	//     Expected output:
	//     ["" "" "" "" "" "einstein", "tesla", "aristotle"]
	//
	names = append(names, "einstein", "tesla", "aristotle")
	s.Show("2nd step", names)

	// ########################################################
	//
	// #3: Overwrite the name slice by creating a new slice
	//     using make().
	//
	//     Adjust the make() function so that it creates a
	//     slice with capacity of 5, and puts the slice pointer
	//     to the first index.
	//
	//     Then append the following names to the slice:
	//
	//     "einstein", "tesla", "aristotle"
	//
	//     Expected output:
	//     ["einstein", "tesla", "aristotle" "" ""]
	//
	//     So: Overwrite and print the names slice.
	//
	names = make([]string, 0, 5)
	names = append(names, "einstein", "tesla", "aristotle")
	s.Show("3rd step", names)

	// ########################################################
	//
	// #4: Copy only the first two elements of the following
	//     array to the last two elements of the `names` slice.
	//
	//     Print the names slice, you should see 5 elements.
	//     So, do not forget extending the slice.
	//
	//     Observe how its backing array stays the same.
	//
	moreNames := [...]string{"plato", "khayyam", "ptolemy"}
	copy(names[3:5], moreNames[:2])
	names = names[:cap(names)]

	s.Show("4th step", names)

	// ########################################################
	//
	// #5:  Only copy the last 3 elements of the `names` slice
	//      to a new slice: `clone`.
	//
	//     Append the first two elements of the `names` to the
	//    `clone`.
	//
	//     Ensure that after appending no new backing array
	//     allocations occur for the `clone` slice.
	//
	//     Print the clone slice before and after the append.
	//
	clone := make([]string, 3, 5)
	copy(clone, names[len(names)-3:])
	s.Show("5th step (before append)", clone)

	clone = append(clone, names[:2]...)
	s.Show("5th step (after append)", clone)

	// ########################################################
	//
	// #6: Slice the `clone` slice between 2nd and 4th (inclusive)
	//     elements into a new slice: `sliced`.
	//
	//     Append "hypatia" to the `sliced`.
	//
	//     Ensure that new backing array allocation "occurs".
	//
	//       Change the 3rd element of the `clone` slice
	//       to "elder".
	//
	//       Doing so should not change any elements of
	//       the `sliced` slice.
	//
	//     Print the `clone` and `sliced` slices.
	//
	//
	sliced := clone[1:4:4]
	sliced = append(sliced, "hypatia")
	clone[2] = "elder"

	s.Show("6th step", clone, sliced)
}

//
// Don't mind about this function.
//
// For printing the slices: You can either use the
// prettyslice package or `fmt.Printf`.
//
func init() {
	s.PrintBacking = true // prints the backing array
	s.MaxPerLine = 10     // prints 10 slice elements per line
	s.Width = 60          // prints 60 character per line
}