クロージャのスコープ

sample.go

package main

import (
  "fmt"
  "math"
)

var k float64 = 1

func main() {
  patternA()
  patternB()
}

func patternA() {
  f1 := newFunc()
  f2 := newFunc()
  f3 := newFunc()

  fmt.Println( f1( 1 ) )
  fmt.Println( f1( 1 ) )

  fmt.Println( f2( 2 ) )
  fmt.Println( f2( 2 ) )

  fmt.Println( f3( 3 ) )
  fmt.Println( f3( 3 ) )

  fmt.Println( f1( 1 ) )
  fmt.Println( f2( 2 ) )
  fmt.Println( f3( 3 ) )
}

func newFunc() func( float64 ) float64 {
  var j float64 = 1

  return func( i float64 ) float64 {
    fmt.Println( "**", i, j )
    j = math.Pow( i, j )
    return j
  }
}

func patternB() {
  f1 := newFuncWithOuterScope()
  f2 := newFuncWithOuterScope()
  f3 := newFuncWithOuterScope()

  fmt.Println( f1( 1 ) )
  fmt.Println( f1( 1 ) )

  fmt.Println( f2( 2 ) )
  fmt.Println( f2( 2 ) )

  fmt.Println( f3( 3 ) )
  fmt.Println( f3( 3 ) )

  fmt.Println( f1( 1 ) )
  fmt.Println( f2( 2 ) )
  fmt.Println( f3( 3 ) )
}

func newFuncWithOuterScope() func( float64 ) float64 {
  return func( i float64 ) float64 {
    fmt.Println( "**", i, k )
    k = math.Pow( i, k )
    return k
  }
}