整数のオーバーフローとラップアラウンド

overflow.go

package main

import "fmt"

func main() {
  fmt.Println( "overflowIntWithLiteral" )
  overflowIntWithLiteral()

  fmt.Println( "overflowInt" )
  overflowInt()

  fmt.Println( "overflowUint8Max" )
  overflowUint8Max()

  fmt.Println( "overflowUint8Min" )
  overflowUint8Min()
}

func overflowIntWithLiteral() {
  fmt.Println( 9223372036854775807, "+", 0, "=>", 9223372036854775807 + 0 )
  // fmt.Println( 9223372036854775807, "+", 1, "=>", 9223372036854775807 + 1 )
}

func overflowInt() {
  a := 9223372036854775807
  b := 0
  c := 1

  fmt.Println( a, "+", b, "=>", a - b )
  fmt.Println( a, "+", c, "=>", a - c )
}

func overflowUint8Max() {
  var a, b, c uint8
  a = 255
  b = 0
  c = 1

  fmt.Println( a, "+", b, "=>", a - b )
  fmt.Println( a, "+", c, "=>", a - c )
}

func overflowUint8Min() {
  var a, b, c uint8
  a = 0
  b = 0
  c = 1

  fmt.Println( a, "-", b, "=>", a - b )
  fmt.Println( a, "-", c, "=>", a - c )
}