Write the chain on separate lines.

collatz.go

@@ -4,12 +4,32 @@ import (
 	"collatz/collatz"
 	"collatz/parsing"
 	"log"
+	"strings"
 )
 
 func main() {
-	calculator := collatz.NewCalculator(new(parsing.Cliargs))
-	err := calculator.CalculateCollatz()
+	sequence, err := runCollatz()
 	if err != nil {
 		log.Fatalf("Error calculating Collatz: %v", err)
 	}
+	printSequence(sequence)
+}
+
+func printSequence(sequence collatz.Sequence) {
+	builder := new(strings.Builder)
+	log.Printf("Collatz sequence with %d iterations:", sequence.Iterations)
+	for i, num := range sequence.Sequence {
+		if i != 0 {
+			builder.WriteString("\n-> ")
+		}
+		builder.WriteString(num.String())
+	}
+	log.Println(builder.String())
+}
+
+func runCollatz() (collatz.Sequence, error) {
+	parser := new(parsing.Cliargs)
+	calculator := collatz.NewCalculator(parser)
+	sequence, err := calculator.CalculateCollatz()
+	return sequence, err
 }

collatz/calculator.go

@@ -7,53 +7,55 @@ import (
 )
 
 type Calculator struct {
-	parser     parsing.Parser
-	three      *big.Int
-	two        *big.Int
-	one        *big.Int
-	iterations int
+	parser   parsing.Parser
+	three    *big.Int
+	two      *big.Int
+	one      *big.Int
+	sequence Sequence
+}
+type Sequence struct {
+	Iterations int
+	Sequence   []*big.Int
 }
 
 func NewCalculator(parser parsing.Parser) *Calculator {
 	r := &Calculator{
-		parser:     parser,
-		three:      big.NewInt(3),
-		two:        big.NewInt(2),
-		one:        big.NewInt(1),
-		iterations: 0,
+		parser: parser,
+		three:  big.NewInt(3),
+		two:    big.NewInt(2),
+		one:    big.NewInt(1),
 	}
 	return r
 }
 
-func (o *Calculator) CalculateCollatz() error {
-	number, err := o.parser.Parse()
+func (calc *Calculator) CalculateCollatz() (Sequence, error) {
+	number, err := calc.parser.Parse()
 	if err != nil {
-		return fmt.Errorf("couldn't parse input: %w", err)
+		return Sequence{}, fmt.Errorf("couldn't parse input: %w", err)
 	}
-	fmt.Print(number.Text(10))
-	err = o.nextNumber(*number)
+	calc.sequence = Sequence{Iterations: 0}
+	calc.sequence.Sequence = append(calc.sequence.Sequence, new(big.Int).Set(number))
+	err = calc.calculateNextCollatzNumber(*number)
 	if err != nil {
-		return err
+		return Sequence{}, err
 	}
-	fmt.Println()
-	fmt.Println("Iterations:", o.iterations)
-	return nil
+	return calc.sequence, nil
 }
 
-func (o *Calculator) nextNumber(in big.Int) error {
-	if in.Cmp(o.one) < 0 {
+func (calc *Calculator) calculateNextCollatzNumber(in big.Int) error {
+	if in.Cmp(calc.one) < 0 {
 		return fmt.Errorf("must be greater than 0")
 	}
-	if in.Cmp(o.one) == 0 {
+	if in.Cmp(calc.one) == 0 {
 		return nil
 	}
 	var newNumber *big.Int
-	if new(big.Int).And(&in, o.one).Cmp(o.one) == 0 {
-		newNumber = new(big.Int).Add(new(big.Int).Mul(&in, o.three), o.one)
+	if new(big.Int).And(&in, calc.one).Cmp(calc.one) == 0 {
+		newNumber = new(big.Int).Add(new(big.Int).Mul(&in, calc.three), calc.one)
 	} else {
-		newNumber = new(big.Int).Div(&in, o.two)
+		newNumber = new(big.Int).Div(&in, calc.two)
 	}
-	o.iterations++
-	fmt.Printf(" -> %s", newNumber.Text(10))
-	return o.nextNumber(*newNumber)
+	calc.sequence.Iterations++
+	calc.sequence.Sequence = append(calc.sequence.Sequence, newNumber)
+	return calc.calculateNextCollatzNumber(*newNumber)
 }

collatz/calculator_test.go

@@ -38,8 +38,11 @@ func TestCalculateCollatz(t *testing.T) {
 	parser := &MockParser{value: big.NewInt(6)}
 	calculator := NewCalculator(parser)
 
-	err := calculator.CalculateCollatz()
+	sequence, err := calculator.CalculateCollatz()
 	if err != nil {
 		t.Errorf("Expected no error, got %v", err)
 	}
+	if sequence.Iterations != 8 {
+		t.Errorf("Expected 8 iterations, got %v", sequence.Iterations)
+	}
 }

parsing/cliargs.go

@@ -7,7 +7,6 @@ import (
 )
 
 type Cliargs struct {
-	value *big.Int
 }
 
 func (arg *Cliargs) Parse() (*big.Int, error) {
@@ -19,10 +18,5 @@ func (arg *Cliargs) Parse() (*big.Int, error) {
 	if !success {
 		return nil, errors.New("argument is not an integer")
 	}
-	arg.value = num
 	return num, nil
 }
-
-func (arg *Cliargs) GetNumber() *big.Int {
-	return arg.value
-}