package main

import "fmt"

// The start of a linked list in Go.
// And some review of pointers
// Created: 11/15/2022  gtowell

// A node in a linked list. Note that the type of the "data"
// could be anything at all, and would usually be another struct
type LL struct {
	dta dataStruct  
	nxt *LL // * indicated that what is stored here is an address
}

// a struct holding data in the linked list
// Unnecessary in this case as the struct is minimal
type dataStruct struct {
	dta int16
}

// toString method for the struct dataStruct
func (dta dataStruct) String() string {
	return fmt.Sprintf("%d", dta.dta)
}

// returns the last 4 digits of the pointer contained in the
// linked list node
func (mll *LL) l4a() string {
	a:= fmt.Sprintf("%p", mll)
	return a[len(a)-4:];
}

// method to print a one line representation of a  LinkedList
// header is some string to identify the particular list 
func (mll *LL) printLL(header string) {
	fmt.Printf("%s: ", header)
	for ;mll!=nil; {
		fmt.Printf("[%s]--> %d  ", mll.l4a(), mll.dta)
		mll=mll.nxt
	}
	fmt.Printf("\n")
}

func main() {
	a := LL{dta: dataStruct{5}}
	b := new(LL) // new pretty much guarantees allocation from heap
	// "new(LL)" makes an instance of LL much line LL{ }, but the initial values are all zeroes. 
	b.dta = dataStruct{10}
	a.nxt = b 
	fmt.Printf("Create A then B, and append B to A\n")
	(&a).printLL("A");
	b.printLL("B");
	c := LL{dta: dataStruct{20}}
	c.nxt = &a; // again & get address
	fmt.Printf("Create C and append A onto C\n")
	c.printLL("C");
}