massive: move a lot of things

25-functions-and-pointers/01-basics/bad.go

@@ -0,0 +1,26 @@
+// 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 showN() {
+	if N == 0 {
+		fmt.Println("showN       : N is zero, increment it.")
+		return
+	}
+	fmt.Printf("showN       : N = %d\n", N)
+}
+
+func incrN() {
+	N++
+}
+
+// you cannot declare a function within the same package with the same name
+// func incrN() {
+// }

25-functions-and-pointers/01-basics/main.go

@@ -0,0 +1,33 @@
+// 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/
+//
+
+//
+// You need run this program like so:
+//   go run .
+//
+// This will magically pass all the go files in the current directory to the
+// Go compiler.
+//
+//
+// BUT NOT like so:
+//   go run main.go
+//
+// Because, the compiler needs to see global.go too
+// It can't magically find global.go — what you give is what you get.
+//
+
+package main
+
+// N is a shared counter which is BAD
+var N int
+
+func main() {
+	showN()
+	incrN()
+	incrN()
+	showN()
+}

25-functions-and-pointers/02-basics/main.go

@@ -0,0 +1,117 @@
+// 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/
+//
+
+//
+// You need run this program like so:
+//   go run .
+//
+// This will magically pass all the go files in the current directory to the
+// Go compiler.
+//
+//
+// BUT NOT like so:
+//   go run main.go
+//
+// Because, the compiler needs to see global.go too
+// It can't magically find global.go — what you give is what you get.
+//
+
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	local := 10
+	show(local)
+
+	incrWrong(local)
+	fmt.Printf("local → %d\n", local)
+
+	// incr(local)
+	local = incr(local)
+	show(local)
+
+	local = incrBy(local, 5)
+	show(local)
+
+	_, err := incrByStr(local, "TWO")
+	if err != nil {
+		fmt.Printf("err   → %s\n", err)
+	}
+
+	local, _ = incrByStr(local, "2")
+	show(local)
+
+	// CHAINING
+
+	// can't save the number back into main's local
+	show(incrBy(local, 2))
+	show(local)
+
+	// can't pass the results of the multiple-value returning func
+	// show(incrByStr(local, "3"))
+
+	// can call showErr directly because it accepts the same types
+	// of parameters as with incrByStr's result values.
+	// local = sanitize(incrByStr(local, "NOPE"))
+	// show(local)
+
+	local = sanitize(incrByStr(local, "2"))
+	show(local)
+
+	local = limit(incrBy(local, 5), 2000)
+	show(local)
+}
+
+func show(n int) {
+	// can't access main's local
+	// fmt.Printf("show : n = %d\n", local)
+	fmt.Printf("show  → n = %d\n", n)
+}
+
+// wrong: incr can't access to main's `local`
+func incrWrong(n int) {
+	// n := local
+	n++
+	// can't return (there are no result values)
+	// return n
+}
+
+func incr(n int) int {
+	n++
+	return n
+}
+
+func incrBy(n, factor int) int {
+	return n * factor
+}
+
+func incrByStr(n int, factor string) (int, error) {
+	m, err := strconv.Atoi(factor)
+	n = incrBy(n, m)
+	return n, err
+}
+
+func sanitize(n int, err error) int {
+	if err != nil {
+		return 0
+	}
+	return n
+}
+
+func limit(n, lim int) (m int) {
+	// var m int
+	m = n
+	if m >= lim {
+		m = lim
+	}
+	// return m
+	return
+}

25-functions-and-pointers/03-refactor-to-funcs/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/03-refactor-to-funcs/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/03-refactor-to-funcs/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/03-refactor-to-funcs/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/03-refactor-to-funcs/main.go

@@ -0,0 +1,62 @@
+// 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 (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+)
+
+func main() {
+	p := newParser()
+
+	// Scan the standard-in line by line
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		p.lines++
+
+		parsed, err := parse(p, in.Text())
+		if err != nil {
+			fmt.Println(err)
+			return
+		}
+
+		domain, visits := parsed.domain, parsed.visits
+
+		// Collect the unique domains
+		if _, ok := p.sum[domain]; !ok {
+			p.domains = append(p.domains, domain)
+		}
+
+		// Keep track of total and per domain visits
+		p.total += visits
+
+		// create and assign a new copy of `visit`
+		p.sum[domain] = result{
+			domain: domain,
+			visits: visits + p.sum[domain].visits,
+		}
+	}
+
+	// Print the visits per domain
+	sort.Strings(p.domains)
+
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+}

25-functions-and-pointers/03-refactor-to-funcs/parser.go

@@ -0,0 +1,53 @@
+// 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"
+	"strconv"
+	"strings"
+)
+
+// result stores the parsed result for a domain
+type result struct {
+	domain string
+	visits int
+	// add more metrics if needed
+}
+
+// parser keep tracks of the parsing
+type parser struct {
+	sum     map[string]result // metrics per domain
+	domains []string          // unique domain names
+	total   int               // total visits for all domains
+	lines   int               // number of parsed lines (for the error messages)
+}
+
+// newParser constructs, initializes and returns a new parser
+func newParser() parser {
+	return parser{sum: make(map[string]result)}
+}
+
+// parse parses a log line and returns the parsed result with an error
+func parse(p parser, line string) (parsed result, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	parsed.domain = fields[0]
+
+	parsed.visits, err = strconv.Atoi(fields[1])
+	if parsed.visits < 0 || err != nil {
+		err = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+		return
+	}
+
+	return
+}

25-functions-and-pointers/04-pass-by-value-semantics/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/04-pass-by-value-semantics/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/04-pass-by-value-semantics/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/04-pass-by-value-semantics/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/04-pass-by-value-semantics/main.go

@@ -0,0 +1,48 @@
+// 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 (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+)
+
+func main() {
+	p := newParser()
+
+	// Scan the standard-in line by line
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		p.lines++
+
+		parsed, err := parse(p, in.Text())
+		if err != nil {
+			fmt.Println(err)
+			break
+		}
+
+		p = update(p, parsed)
+	}
+
+	// Print the visits per domain
+	sort.Strings(p.domains)
+
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+}

25-functions-and-pointers/04-pass-by-value-semantics/parse.go

@@ -0,0 +1,71 @@
+// 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"
+	"strconv"
+	"strings"
+)
+
+// result stores metrics for a domain
+type result struct {
+	domain string
+	visits int
+	// add more metrics if needed
+}
+
+// parser keep tracks of the parsing
+type parser struct {
+	sum     map[string]result // metrics per domain
+	domains []string          // unique domain names
+	total   int               // total visits for all domains
+	lines   int               // number of parsed lines (for the error messages)
+}
+
+func newParser() parser {
+	return parser{sum: make(map[string]result)}
+}
+
+func parse(p parser, line string) (parsed result, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	parsed.domain = fields[0]
+
+	parsed.visits, err = strconv.Atoi(fields[1])
+	if parsed.visits < 0 || err != nil {
+		err = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+		return
+	}
+
+	return
+}
+
+func update(p parser, parsed result) parser {
+	domain, visits := parsed.domain, parsed.visits
+
+	// Collect the unique domains
+	if _, ok := p.sum[domain]; !ok {
+		p.domains = append(p.domains, domain)
+	}
+
+	// Keep track of total and per domain visits
+	p.total += visits
+
+	// create and assign a new copy of `visit`
+	p.sum[domain] = result{
+		domain: domain,
+		visits: visits + p.sum[domain].visits,
+	}
+
+	return p
+}

25-functions-and-pointers/05-pointers/main.go

@@ -0,0 +1,39 @@
+// 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 counter byte = 100
+	P := &counter
+	V := *P
+
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("P       : %-16p address: %-16p *P: %-16d\n", P, &P, *P)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+
+	V = 200
+	fmt.Println()
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("P       : %-16p address: %-16p *P: %-16d\n", P, &P, *P)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+
+	V = counter // reset the V to counter's initial value
+	counter++
+	fmt.Println()
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("P       : %-16p address: %-16p *P: %-16d\n", P, &P, *P)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+
+	*P = 25
+	fmt.Println()
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("P       : %-16p address: %-16p *P: %-16d\n", P, &P, *P)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+}

25-functions-and-pointers/06-pointers-basic-examples/main.go

@@ -0,0 +1,63 @@
+// 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 (
+		counter int
+		V       int
+		P       *int
+	)
+
+	if P == nil {
+		fmt.Printf("P is nil and its address is %p\n", P)
+	}
+
+	counter = 100 // counter is an int variable
+	P = &counter  // P is a pointer int variable
+	V = *P        // V is a int variable (a copy of counter)
+
+	if P == &counter {
+		fmt.Printf("P's address is equal to counter: %p == %p\n", P, &counter)
+	}
+
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("P       : %-16p address: %-16p *P: %-16d\n", P, &P, *P)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+
+	fmt.Println("\n••••• CHANGE: counter")
+	counter = 10 // V doesn't change because it's a copy
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+	fmt.Printf("V       : %-16d address: %-16p\n", V, &V)
+
+	fmt.Println("\n••••• CHANGE IN: passVal")
+	counter = passVal(counter)
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+
+	fmt.Println("\n••••• CHANGE IN: passPtrVal")
+	passPtrVal(&counter) // same as passPtrVal(&counter) (no need to return)
+	fmt.Printf("counter : %-16d address: %-16p\n", counter, &counter)
+}
+
+// *pn is a int pointer variable (copy of P)
+func passPtrVal(pn *int) {
+	fmt.Printf("pn      : %-16p address: %-16p *pn: %d\n", pn, &pn, *pn)
+
+	// pointers can breach function isolation borders
+	*pn++ // counter changes because `pn` points to `counter` — (*pn)++
+	fmt.Printf("pn      : %-16p address: %-16p *pn: %d\n", pn, &pn, *pn)
+}
+
+// n is a int variable (copy of counter)
+func passVal(n int) int {
+	n = 50 // counter doesn't change because `n` is a copy
+	fmt.Printf("n       : %-16d address: %-16p\n", n, &n)
+	return n
+}

25-functions-and-pointers/07-pointers-composites/main.go

@@ -0,0 +1,141 @@
+// 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"
+	"strings"
+)
+
+func main() {
+	fmt.Println("••••• ARRAYS")
+	arrays()
+
+	fmt.Println("\n••••• SLICES")
+	slices()
+
+	fmt.Println("\n••••• MAPS")
+	maps()
+
+	fmt.Println("\n••••• STRUCTS")
+	structs()
+}
+
+// -----------------------------------------------------------------------------
+
+type house struct {
+	name  string
+	rooms int
+}
+
+func structs() {
+	myHouse := house{name: "My House", rooms: 5}
+
+	addRoom(myHouse)
+
+	// fmt.Printf("%+v\n", myHouse)
+	fmt.Printf("structs()     : %p %+v\n", &myHouse, myHouse)
+
+	addRoomPtr(&myHouse)
+	fmt.Printf("structs()     : %p %+v\n", &myHouse, myHouse)
+
+	fmt.Printf("&myHouse.name : %p\n", &myHouse.name)
+	fmt.Printf("&myHouse.rooms: %p\n", &myHouse.rooms)
+}
+
+func addRoom(h house) {
+	h.rooms++
+	fmt.Printf("addRoom()     : %p %+v\n", &h, h)
+}
+
+func addRoomPtr(h *house) {
+	// (*h).rooms++
+	h.rooms++
+	fmt.Printf("addRoomPtr()  : %p %+v\n", h, h)
+}
+
+// -----------------------------------------------------------------------------
+
+func maps() {
+	confused := map[string]int{"one": 2, "two": 1}
+
+	fix(confused)
+
+	fmt.Println(confused)
+
+	// &confused["one"]
+}
+
+func fix(m map[string]int) {
+	m["one"] = 1
+	m["two"] = 2
+	m["three"] = 3
+}
+
+// -----------------------------------------------------------------------------
+
+func slices() {
+	dirs := []string{"up", "down", "left", "right"}
+
+	up(dirs)
+	fmt.Printf("slices list   : %p %q\n", &dirs, dirs)
+
+	upPtr(&dirs)
+	fmt.Printf("slices list   : %p %q\n", &dirs, dirs)
+}
+
+func up(list []string) {
+	for i := range list {
+		list[i] = strings.ToUpper(list[i])
+		fmt.Printf("up.list[%d]    : %p\n", i, &list[i])
+	}
+	// *list = append(*list, "HEISEN BUG")
+	list = append(list, "HEISEN BUG")
+
+	fmt.Printf("up list       : %p %q\n", &list, list)
+}
+
+func upPtr(list *[]string) {
+	lv := *list
+
+	for i := range lv {
+		lv[i] = strings.ToUpper(lv[i])
+	}
+	*list = append(*list, "HEISEN BUG")
+
+	fmt.Printf("upPtr list    : %p %q\n", list, list)
+}
+
+// -----------------------------------------------------------------------------
+
+func arrays() {
+	nums := [...]int{1, 2, 3}
+
+	incr(nums)
+	fmt.Printf("arrays nums   : %p\n", &nums)
+	fmt.Println(nums)
+
+	incrByPtr(&nums)
+	fmt.Println(nums)
+}
+
+func incr(nums [3]int) {
+	fmt.Printf("incr nums     : %p\n", &nums)
+
+	for i := range nums {
+		nums[i]++
+		fmt.Printf("incr.nums[%d]  : %p\n", i, &nums[i])
+	}
+}
+
+func incrByPtr(nums *[3]int) {
+	for i := range nums {
+		nums[i]++
+		// (*nums)[i]++
+	}
+}

25-functions-and-pointers/08-log-parser-pointers/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08-log-parser-pointers/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08-log-parser-pointers/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08-log-parser-pointers/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08-log-parser-pointers/main.go

@@ -0,0 +1,36 @@
+// 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 (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	in := bufio.NewScanner(os.Stdin)
+
+	p := newParser()
+
+	for in.Scan() {
+		add(p, in.Text())
+	}
+
+	for _, name := range p.domains {
+		// vis := p.sum[d.name]
+		d := p.sum[name]
+
+		fmt.Printf("%-25s -> %d\n", d.name, d.visits)
+	}
+	fmt.Printf("\n%-25s -> %d\n", "TOTAL", p.total)
+
+	if p.lerr != nil {
+		fmt.Printf("> Err: %s\n", p.lerr)
+	}
+}

25-functions-and-pointers/08-log-parser-pointers/parser.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// TODO: add add() func
+// TODO: add error handling (variadics)
+// TODO: add iterator func values
+// TODO: add summarizer to main()
+
+// domain represents a single domain log record
+type domain struct {
+	name   string
+	visits int
+}
+
+// parser parses a log file and provides an iterator to iterate upon the domains
+//
+// the parser struct is carefully crafted to be usable using its zero values except the map field
+type parser struct {
+	// sum     map[string]int // visits per unique domain
+	// domains []domain       // unique domain names
+	sum     map[string]domain // visits per unique domain
+	domains []string          // unique domain names
+
+	total int   // total visits to all domains
+	lines int   // number of parsed lines (for the error messages)
+	lerr  error // saves the last error occurred
+}
+
+// newParser creates and returns a new parser.
+func newParser() *parser {
+	// return &parser{sum: make(map[string]int)}
+	return &parser{sum: make(map[string]domain)}
+}
+
+// add parses the given line and saves the result to the internal list of
+// domains. it doesn't add the record when the parsing fails.
+func add(p *parser, line string) {
+	// if there was a previous error do not add
+	if p.lerr != nil {
+		return
+	}
+
+	dom, err := parse(p, line)
+
+	// store only the last error
+	if err != nil {
+		p.lerr = err
+		return
+	}
+
+	push(p, dom)
+}
+
+// parse parses the given text and returns a domain struct
+func parse(p *parser, line string) (dom domain, err error) {
+	p.lines++
+
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	dom.name = fields[0]
+
+	dom.visits, err = strconv.Atoi(fields[1])
+	if dom.visits < 0 || err != nil {
+		err = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+	}
+
+	return
+}
+
+// push pushes the given domain to the internal list of domains.
+// it also increases the total visits for all the domains.
+func push(p *parser, d domain) {
+	// TODO:
+	// if _, ok := p.sum[d.name]; !ok {
+	// 	p.domains = append(p.domains, d)
+	// }
+
+	// p.sum[d.name] += d.visits
+	// p.total += d.visits
+	name := d.name
+
+	// collect the unique domains
+	if _, ok := p.sum[name]; !ok {
+		p.domains = append(p.domains, name)
+	}
+
+	p.total += d.visits
+	d.visits += p.sum[name].visits
+	p.sum[name] = d
+}

25-functions-and-pointers/08x-log-parser-pointers/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08x-log-parser-pointers/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08x-log-parser-pointers/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08x-log-parser-pointers/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/08x-log-parser-pointers/main.go

@@ -0,0 +1,57 @@
+// 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 (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	in := bufio.NewScanner(os.Stdin)
+
+	p := newParser()
+	for in.Scan() {
+		// dom, err := parse(p, in.Text())
+		// if err != nil {
+		// 	fmt.Println(err)
+		// 	return
+		// }
+
+		// p = push(p, dom)
+
+		add(p, in.Text())
+	}
+
+	summarize(p)
+	dumpErrs(in.Err(), err(p))
+}
+
+// funcs not always need to be reused.
+// here, it tells about what it does: it summarizes the parsing result.
+func summarize(p *parser) {
+	// multiple iterators can be created. each one remembers the last
+	// read domain record.
+
+	next, cur := iterator(p)
+	for next() {
+		dom := cur()
+		fmt.Printf("%-25s -> %d\n", dom.name, dom.visits)
+	}
+	fmt.Printf("\n%-25s -> %d\n", "TOTAL", p.total)
+}
+
+// this variadic func simplifies the multiple error handling
+func dumpErrs(errs ...error) {
+	for _, err := range errs {
+		if err != nil {
+			fmt.Printf("> Err: %s\n", err)
+		}
+	}
+}

25-functions-and-pointers/08x-log-parser-pointers/parser.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// domain represents a domain log record
+type domain struct {
+	name   string
+	visits int
+}
+
+// parser parses a log file and provides an iterator to iterate upon the domains
+//
+// the parser struct is carefully crafted to be usable using its zero values except the map field
+type parser struct {
+	sum     map[string]domain // visits per unique domain
+	domains []string          // unique domain names
+	total   int               // total visits to all domains
+	lines   int               // number of parsed lines (for the error messages)
+	lerr    error             // saves the last error occurred
+}
+
+// newParser creates and returns a new parser.
+func newParser() *parser {
+	return &parser{sum: make(map[string]domain)}
+}
+
+// add parses the given line and saves the result to the internal list of
+// domains. it doesn't add the record when the parsing fails.
+func add(p *parser, line string) {
+	// if there was a previous error do not add
+	if p.lerr != nil {
+		return
+	}
+
+	dom, err := parse(p, line)
+
+	// store only the last error
+	if err != nil {
+		p.lerr = err
+		return
+	}
+
+	push(p, dom)
+}
+
+// iterator returns two functions for iterating over domains.
+// next = returns true when there are more domains to iterate on.
+// cur  = returns the current domain
+func iterator(p *parser) (next func() bool, cur func() domain) {
+	// remember the last received line
+	var last int
+
+	next = func() bool {
+		defer func() { last++ }()
+		return len(p.domains) > last
+	}
+
+	cur = func() domain {
+		// return a copy so the caller cannot change it
+		name := p.domains[last-1]
+		return p.sum[name]
+	}
+
+	return
+}
+
+// error returns the last error occurred
+func err(p *parser) error {
+	return p.lerr
+}
+
+// parse parses the given text and returns a domain struct
+func parse(p *parser, line string) (dom domain, err error) {
+	p.lines++ // increase the parsed line counter (only write is here)
+
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	name, visits := fields[0], fields[1]
+
+	n, err := strconv.Atoi(visits)
+	if n < 0 || err != nil {
+		err = fmt.Errorf("wrong input: %q (line #%d)", visits, p.lines)
+		return
+	}
+
+	return domain{name: name, visits: n}, nil
+}
+
+// push pushes the given domain to the internal list of domains.
+// it also increases the total visits for all the domains.
+func push(p *parser, d domain) {
+	name := d.name
+
+	// collect the unique domains
+	if _, ok := p.sum[name]; !ok {
+		p.domains = append(p.domains, name)
+	}
+
+	p.total += d.visits
+	d.visits += p.sum[name].visits
+	p.sum[name] = d
+}

25-functions-and-pointers/README.md

@@ -0,0 +1 @@
+This section is in progress. I'm working hard to update the course all the time. Hold on!

25-functions-and-pointers/_WIP/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/_WIP/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/_WIP/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions-and-pointers/_WIP/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10