add: calculator example to x-tba

x-tba/foundations/calc/01-shortdecl-int-conv/main.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: multi-return funcs, %v, and _
+
+	a, _ := strconv.Atoi(os.Args[1])
+	b, _ := strconv.Atoi(os.Args[2])
+
+	fmt.Printf("%v + %v = %v\n", a, b, a+b)
+}

x-tba/foundations/calc/02-if/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: if
+
+	if len(os.Args) != 3 {
+		fmt.Println("Usage: calc <number1> <number2>")
+		return
+	}
+
+	a, _ := strconv.Atoi(os.Args[1])
+	b, _ := strconv.Atoi(os.Args[2])
+
+	fmt.Printf("%v + %v = %v\n", a, b, a+b)
+}

x-tba/foundations/calc/03-floats-conv/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: floats encompass integers too
+
+	if len(os.Args) != 3 {
+		fmt.Println("Usage: calc <number1> <number2>")
+		return
+	}
+
+	a, _ := strconv.ParseFloat(os.Args[1], 64)
+	b, _ := strconv.ParseFloat(os.Args[2], 64)
+
+	fmt.Printf("%v + %v = %v\n", a, b, a+b)
+}

x-tba/foundations/calc/04-error-handling/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: error handling + short decl. assignment
+
+	if len(os.Args) != 3 {
+		fmt.Println("Usage: calc <number1> <number2>")
+		return
+	}
+
+	a, err := strconv.ParseFloat(os.Args[1], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	b, err := strconv.ParseFloat(os.Args[2], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	fmt.Printf("%v + %v = %v\n", a, b, a+b)
+}

x-tba/foundations/calc/05-switch/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: switch
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	a, err := strconv.ParseFloat(os.Args[1], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	b, err := strconv.ParseFloat(os.Args[3], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	var (
+		op  = os.Args[2]
+		res float64
+	)
+
+	switch op {
+	case "+":
+		res = a + b
+	case "-":
+		res = a - b
+	case "*":
+		res = a * b
+	case "/":
+		res = a / b
+	}
+
+	fmt.Printf("%v %v %v = %v\n", a, op, b, res)
+}

x-tba/foundations/calc/06-switch/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: switch default + multiple case
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	a, err := strconv.ParseFloat(os.Args[1], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	b, err := strconv.ParseFloat(os.Args[3], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	var (
+		op  = os.Args[2]
+		res float64
+	)
+
+	switch op {
+	case "+", "plus":
+		op, res = "+", a+b
+	case "-", "minus":
+		op, res = "-", a-b
+	case "*", "times":
+		op, res = "*", a*b
+	case "/", "div":
+		op, res = "/", a/b
+	default:
+		fmt.Println("Please provide a valid operation.")
+		return
+	}
+
+	fmt.Printf("%v %v %v = %v\n", a, op, b, res)
+}

x-tba/foundations/calc/07/main.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: modulo operator and type conversion
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	a, err := strconv.ParseFloat(os.Args[1], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	b, err := strconv.ParseFloat(os.Args[3], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	var (
+		op  = os.Args[2]
+		res float64
+	)
+
+	switch op {
+	case "+", "plus":
+		op, res = "+", a+b
+	case "-", "minus":
+		op, res = "-", a-b
+	case "*", "times":
+		op, res = "*", a*b
+	case "/", "div":
+		op, res = "/", a/b
+	case "%", "mod":
+		res = float64(int(a) % int(b))
+	default:
+		fmt.Println("Please provide a valid operation.")
+		return
+	}
+
+	fmt.Printf("%v %v %v = %v\n", a, op, b, res)
+}

x-tba/foundations/calc/08-funcs/main.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: many - split this
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	var (
+		a, b float64
+		err  error
+	)
+
+	if a, err = parse(os.Args[1]); err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	if b, err = parse(os.Args[3]); err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	op := os.Args[2]
+	res, err := calc(a, b, op)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	fmt.Printf("%v %s %v = %v\n", a, op, b, res)
+}
+
+func parse(snum string) (n float64, err error) {
+	n, err = strconv.ParseFloat(snum, 64)
+	if err != nil {
+		err = errors.New("Please provide a valid number")
+	}
+	return
+}
+
+func calc(a, b float64, op string) (res float64, err error) {
+	switch op {
+	case "+", "plus":
+		op, res = "+", a+b
+	case "-", "minus":
+		op, res = "-", a-b
+	case "*", "times":
+		op, res = "*", a*b
+	case "/", "div":
+		op, res = "/", a/b
+	case "%", "mod":
+		res = float64(int(a) % int(b))
+	default:
+		return 0, errors.New("Wrong operation: '" + op + "'")
+	}
+	return
+}

x-tba/foundations/calc/09-packages/calc/calc.go

@@ -0,0 +1,36 @@
+package calc
+
+import (
+	"errors"
+	"strconv"
+)
+
+// Parse ...
+func Parse(snum string) (n float64, err error) {
+	n, err = strconv.ParseFloat(snum, 64)
+	if err != nil {
+		// Don't loose the actual error for debugging
+		err = errors.New("Please provide a valid number: " +
+			err.Error())
+	}
+	return
+}
+
+// Do ...
+func Do(a, b float64, op string) (res float64, err error) {
+	switch op {
+	case "+", "plus":
+		op, res = "+", a+b
+	case "-", "minus":
+		op, res = "-", a-b
+	case "*", "times":
+		op, res = "*", a*b
+	case "/", "div":
+		op, res = "/", a/b
+	case "%", "mod":
+		res = float64(int(a) % int(b))
+	default:
+		return 0, errors.New("Wrong operation: '" + op + "'")
+	}
+	return
+}

x-tba/foundations/calc/09-packages/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/inancgumus/learngo/x-tba/foundations/calc/09-packages/calc"
+)
+
+func main() {
+	// lesson: packaging
+
+	// separate dependencies like getting and validating
+	// user data as in here.
+	//
+	// we only put calc to another packages, not the other
+	// stuff.
+	//
+	// so, we can reuse the same calc package and use it
+	// over a web api if we want.
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	var (
+		a, b float64
+		err  error
+	)
+
+	if a, err = calc.Parse(os.Args[1]); err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	if b, err = calc.Parse(os.Args[3]); err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	op := os.Args[2]
+	res, err := calc.Do(a, b, op)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	fmt.Printf("%v %s %v = %v\n", a, op, b, res)
+}

x-tba/foundations/calc/calc-scanner/calculations.txt

@@ -0,0 +1,4 @@
+4 + 5
+6.5 + 2
+5 - 3
+q

x-tba/foundations/calc/calc-scanner/main.go

@@ -0,0 +1,66 @@
+/*
+go run main.go < ./calculations.txt
+
+If you're not on Linux or OS X, etc but on Windows,
+Then, use Windows PowerShell to do the same thing.
+*/
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+// After functions, you'll see that how we're going to refactor this
+// into a more readable version.
+
+func main() {
+	const (
+		promptChar     = "> "
+		errWrongOp     = "%s operation is not supported\n"
+		errWrongFormat = "operation is not recognized\n"
+		usage          = `
+usage: number operation number
+quit : type q to quit
+examples:
+  3 + 5
+  5 - 3
+`
+	)
+
+	fmt.Println(strings.TrimSpace(usage))
+
+	for s := bufio.NewScanner(os.Stdin); ; {
+		var (
+			a, b, res float64
+			op        string
+		)
+
+		fmt.Print(promptChar, " ")
+		if !s.Scan() {
+			break
+		}
+
+		_, err := fmt.Sscanf(s.Text(), "%f %s %f", &a, &op, &b)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, errWrongFormat)
+			continue
+		}
+
+		switch op {
+		case "+":
+			res = a + b
+		case "-":
+			res = a - b
+		default:
+			fmt.Printf(errWrongOp, op)
+			continue
+		}
+
+		fmt.Printf("%g %s %g = %g\n", a, op, b, res)
+	}
+
+	fmt.Println("bye.")
+}