The evolution history of Go programmers

package fac

func Factorial(n int) int {
 res := 1

 for i := 1; i <= n; i++ {
  res *= i
 }

 return res
}

package fac

func Factorial(n int) int {
 if n == 0 {
  return 1
 } else {
  return Factorial(n - 1) * n
 }
}

package fac

func Factorial(n interface{}) interface{} {
 v, valid := n.(int)
 if !valid {
  return 0
 }

 res := 1

 for i := 1; i <= v; i++ {
  res *= i
 }

 return res
}

package fac

import "sync"

func Factorial(n int) int {
 var (
  left, right = 1, 1
  wg sync.WaitGroup
 )

 wg.Add(2)

 pivot := n / 2

 go func() {
  for i := 1; i < pivot; i++ {
   left *= i
  }

  wg.Done()
 }()

 go func() {
  for i := pivot; i <= n; i++ {
   right *= i
  }

  wg.Done()
 }()

 wg.Wait()

 return left * right
}

package fac

func Factorial(n int) <-chan int {
 ch := make(chan int)

 go func() {
  prev := 1

  for i := 1; i <= n; i++ {
   v := prev * i

   ch <- v

   prev = v
  }

  close(ch)
 }()

 return ch
}

package fac

/**
 * @see https://en.wikipedia.org/wiki/Factorial
 */
type IFactorial interface {
 CalculateFactorial() int
}

// FactorialImpl implements IFactorial.
var _ IFactorial = (*FactorialImpl)(nil)

/**
 * Used to find factorial of the n.
 */
type FactorialImpl struct {
 /**
  * The n.
  */
 n int
}

/**
 * Constructor of the FactorialImpl.
 *
 * @param n the n.
 */
func NewFactorial(n int) *FactorialImpl {
 return &FactorialImpl{
  n: n,
 }
}

/**
 * Gets the n to use in factorial function.
 *
 * @return int.
 */
func (this *FactorialImpl) GetN() int {
 return this.n
}

/**
 * Sets the n to use in factorial function.
 *
 * @param n the n.
 * @return void.
 */
func (this *FactorialImpl) SetN(n int) {
 this.n = n
}

/**
 * Returns factorial of the n.
 *
 * @todo remove "if" statement. Maybe we should use a factory or somthing?
 *
 * @return int.
 */
func (this *FactorialImpl) CalculateFactorial() int {
 if this.n == 0 {
  return 1
 }

 n := this.n
 this.n = this.n - 1

 return this.CalculateFactorial() * n
}

package fac

// Factorial returns n!.
func Factorial(n int) int {
 res := 1

 for i := 1; i <= n; i++ {
  res *= i
 }

 return res
}

package fac

// Factorial returns n!.
func Factorial(n int) int {
 res := 1

 for i := 1; i <= n; i++ {
  res *= i
 }

 return res
}