add: log parser pointer examples

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

@@ -26,7 +26,7 @@ func main() {
 		parsed, err := parse(p, in.Text())
 		if err != nil {
 			fmt.Println(err)
-			break
+			return
 		}
 
 		p = update(p, parsed)

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

@@ -13,7 +13,7 @@ import (
 	"strings"
 )
 
-// result stores metrics for a domain
+// result stores the parsed result for a domain
 type result struct {
 	domain string
 	visits int
@@ -28,10 +28,12 @@ type parser struct {
 	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 {
@@ -50,6 +52,7 @@ func parse(p parser, line string) (parsed result, err error) {
 	return
 }
 
+// update updates the parser for the given parsing result
 func update(p parser, parsed result) parser {
 	domain, visits := parsed.domain, parsed.visits
 

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

@@ -11,30 +11,44 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"sort"
+	"strings"
 )
 
 func main() {
-	in := bufio.NewScanner(os.Stdin)
-
 	p := newParser()
 
+	in := bufio.NewScanner(os.Stdin)
 	for in.Scan() {
-		add(p, in.Text())
+		parsed := parse(&p, in.Text())
+		update(&p, parsed)
 	}
 
-	for _, name := range p.domains {
+	summarize(p)
-		// vis := p.sum[d.name]
+	dumpErrs([]error{in.Err(), p.lerr})
-		d := p.sum[name]
+}
 
-		fmt.Printf("%-25s -> %d\n", d.name, d.visits)
+// summarize summarizes and prints the parsing result
-	}
+func summarize(p parser) {
-	fmt.Printf("\n%-25s -> %d\n", "TOTAL", p.total)
+	sort.Strings(p.domains)
 
-	if p.lerr != nil {
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
-		fmt.Println("> Err:", p.lerr)
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
 	}
 
-	if err := in.Err(); err != nil {
+	// 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)
 		}
+	}
 }

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

@@ -1,3 +1,10 @@
+// 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 (
@@ -6,94 +13,71 @@ import (
 	"strings"
 )
 
-// TODO: add add() func
+// result stores the parsed result for a domain
-// TODO: add error handling (variadics)
+type result struct {
-// TODO: add iterator func values
+	domain string
-// TODO: add summarizer to main()
-
-// domain represents a single domain log record
-type domain struct {
-	name   string
 	visits int
+	// add more metrics if needed
 }
 
-// parser parses a log file and provides an iterator to iterate upon the domains
+// parser keep tracks of the parsing
-//
-// 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
+	sum     map[string]result // metrics per domain
-	// domains []domain       // unique domain names
-	sum     map[string]domain // visits per unique domain
 	domains []string          // unique domain names
-
+	total   int               // total visits for all domains
-	total int   // total visits to all domains
 	lines   int               // number of parsed lines (for the error messages)
-	lerr  error // saves the last error occurred
+	lerr    error             // the last error occurred
 }
 
-// newParser creates and returns a new parser.
+// newParser constructs, initializes and returns a new parser
-func newParser() *parser {
+func newParser() parser {
-	// return &parser{sum: make(map[string]int)}
+	return parser{sum: make(map[string]result)}
-	return &parser{sum: make(map[string]domain)}
 }
 
-// add parses the given line and saves the result to the internal list of
+// parse parses a log line and returns the parsed result with an error
-// domains. it doesn't add the record when the parsing fails.
+func parse(p *parser, line string) (parsed result) {
-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)
+		p.lerr = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
 		return
 	}
 
-	dom.name = fields[0]
+	parsed.domain = fields[0]
 
-	dom.visits, err = strconv.Atoi(fields[1])
+	var err error
-	if dom.visits < 0 || err != nil {
+
-		err = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+	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
 }
 
-// push pushes the given domain to the internal list of domains.
+// update updates the errors for the given parsing result
-// it also increases the total visits for all the domains.
+func update(p *parser, parsed result) {
-func push(p *parser, d domain) {
+	if p.lerr != nil {
-	// TODO:
+		return
-	// 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
+	domain, visits := parsed.domain, parsed.visits
-	d.visits += p.sum[name].visits
+
-	p.sum[name] = d
+	// 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,
+	}
 }

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

@@ -1,57 +0,0 @@
-// 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

@@ -1,110 +0,0 @@
-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/09-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)
+		}
+	}
+}

25-functions-and-pointers/09-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
+}

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

@@ -1,6 +0,0 @@
-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

@@ -1,6 +0,0 @@
-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

@@ -1,6 +0,0 @@
-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

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

x-tba/log-parser-json/log.txt

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

x-tba/log-parser-json/log_err_missing.txt

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

x-tba/log-parser-json/log_err_negative.txt

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

x-tba/log-parser-json/log_err_str.txt

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

x-tba/log-parser-json/main.go

@@ -1,97 +0,0 @@
-// 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"
-	"encoding/json"
-	"fmt"
-	"os"
-	"sort"
-	"strconv"
-	"strings"
-)
-
-// Visit stores metrics for a domain
-type Visit struct {
-	Domain string `json:"domain"`
-	Total  int    `json:"total_visits"`
-	// add more metrics if needed
-}
-
-// Parser keep tracks of the parsing
-type Parser struct {
-	Sum     map[string]Visit `json:"visits_per_domain"` // metrics per domain
-	Domains []string         `json:"unique_domains"`    // unique domain names
-	Total   int              `json:"total_visits"`      // total visits for all domains
-	Lines   int              `json:"-"`                 // number of parsed lines (for the error messages)
-}
-
-func main() {
-	p := Parser{Sum: make(map[string]Visit)}
-
-	// Scan the standard-in line by line
-	in := bufio.NewScanner(os.Stdin)
-	for in.Scan() {
-		p.Lines++
-
-		// Parse the fields
-		fields := strings.Fields(in.Text())
-		if len(fields) != 2 {
-			fmt.Printf("wrong input: %v (line #%d)\n", fields, p.Lines)
-			return
-		}
-
-		// Sum the total visits per domain
-		visits, err := strconv.Atoi(fields[1])
-		if visits < 0 || err != nil {
-			fmt.Printf("wrong input: %q (line #%d)\n", fields[1], p.Lines)
-			return
-		}
-
-		name := fields[0]
-
-		// Collect the unique domains
-		if _, ok := p.Sum[name]; !ok {
-			p.Domains = append(p.Domains, name)
-		}
-
-		// Keep track of total and per domain visits
-		p.Total += visits
-
-		// You cannot assign to composite values
-		// p.Sum[name].Total += visits
-
-		// create and assign a new copy of `visit`
-		p.Sum[name] = Visit{
-			Domain: name,
-			Total:  visits + p.Sum[name].Total,
-		}
-	}
-
-	// Print the visits per domain
-	sort.Strings(p.Domains)
-
-	// fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
-	// fmt.Println(strings.Repeat("-", 45))
-
-	// for _, name := range p.Domains {
-	// 	visits := p.Sum[name]
-	// 	fmt.Printf("%-30s %10d\n", name, visits.Total)
-	// }
-
-	// // Print the total visits for all domains
-	// fmt.Printf("\n%-30s %10d\n", "TOTAL", p.Total)
-
-	// if err := in.Err(); err != nil {
-	// 	fmt.Println("> Err:", err)
-	// }
-
-	s, _ := json.MarshalIndent(p, "", "\t")
-	fmt.Println(string(s))
-}