reorganize: starting with funcs

26-pointers/01-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)
+}

26-pointers/02-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
+}

26-pointers/03-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]++
+	}
+}

26-pointers/04-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

26-pointers/04-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

26-pointers/04-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

26-pointers/04-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

26-pointers/04-log-parser-pointers/main.go

@@ -0,0 +1,54 @@
+// 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()
+
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		parsed := parse(&p, in.Text())
+		update(&p, parsed)
+	}
+
+	summarize(p)
+	dumpErrs([]error{in.Err(), p.lerr})
+}
+
+// summarize summarizes and prints the parsing result
+func summarize(p parser) {
+	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)
+}
+
+// dumpErrs simplifies handling multiple errors
+func dumpErrs(errs []error) {
+	for _, err := range errs {
+		if err != nil {
+			fmt.Println("> Err:", err)
+		}
+	}
+}

26-pointers/04-log-parser-pointers/parser.go

@@ -0,0 +1,83 @@
+// 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)
+	lerr    error             // the last error occurred
+}
+
+// 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) {
+	if p.lerr != nil {
+		return
+	}
+
+	p.lines++
+
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		p.lerr = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	parsed.domain = fields[0]
+
+	var err error
+
+	parsed.visits, err = strconv.Atoi(fields[1])
+	if parsed.visits < 0 || err != nil {
+		p.lerr = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+	}
+	return
+}
+
+// update updates the errors for the given parsing result
+func update(p *parser, parsed result) {
+	if p.lerr != nil {
+		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,
+	}
+}

26-pointers/05-log-parser-pointers-vs-values/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

26-pointers/05-log-parser-pointers-vs-values/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

26-pointers/05-log-parser-pointers-vs-values/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

26-pointers/05-log-parser-pointers-vs-values/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

26-pointers/05-log-parser-pointers-vs-values/main.go

@@ -0,0 +1,51 @@
+// 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()
+
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		update(p, parse(p, in.Text()))
+	}
+
+	summarize(p)
+	dumpErrs([]error{in.Err(), err(p)})
+}
+
+// summarize summarizes and prints the parsing result
+func summarize(p *parser) {
+	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)
+	}
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+}
+
+// dumpErrs simplifies handling multiple errors
+func dumpErrs(errs []error) {
+	for _, err := range errs {
+		if err != nil {
+			fmt.Println("> Err:", err)
+		}
+	}
+}

26-pointers/05-log-parser-pointers-vs-values/parser.go

@@ -0,0 +1,88 @@
+// 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)
+	lerr    error             // the last error occurred
+}
+
+// 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) {
+	if p.lerr != nil {
+		return
+	}
+
+	p.lines++
+
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		p.lerr = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	parsed.domain = fields[0]
+
+	var err error
+
+	parsed.visits, err = strconv.Atoi(fields[1])
+	if parsed.visits < 0 || err != nil {
+		p.lerr = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+	}
+	return
+}
+
+// update updates the errors for the given parsing result
+func update(p *parser, parsed result) {
+	if p.lerr != nil {
+		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,
+	}
+}
+
+// err returns the last error encountered
+func err(p *parser) error {
+	return p.lerr
+}