go_workshop/chapter_04/exercise_4.22/main.go

package main

import (
  "errors"
  "fmt"
)

func doubler(v interface{}) (string, error) {

  switch t := v.(type) {
  case string:
    return t + t, nil
  case bool:
    if t {
      return "truetrue", nil
    }
    return "falsefalse", nil
  case float32, float64:
    if f, ok := t.(float64); ok {
      return fmt.Sprint(f * 2), nil
    }
    return fmt.Sprint(t.(float32) * 2), nil
  case int:
    return fmt.Sprint(t * 2), nil
  case int8:
    return fmt.Sprint(t * 2), nil
  case int16:
    return fmt.Sprint(t * 2), nil
  case int32:
    return fmt.Sprint(t * 2), nil
  case int64:
    return fmt.Sprint(t * 2), nil
  case uint:
    return fmt.Sprint(t * 2), nil
  case uint8:
    return fmt.Sprint(t * 2), nil
  case uint16:
    return fmt.Sprint(t * 2), nil
  case uint32:
    return fmt.Sprint(t * 2), nil
  case uint64:
    return fmt.Sprint(t * 2), nil
  default:
    return "", errors.New("unsupported type passed")
  }

}

func main() {

  res, _ := doubler(-5)
  fmt.Println("-5:  ", res)
  res, _ = doubler(5)
  fmt.Println("5:   ", res)
  res, _ = doubler("yum")
  fmt.Println("yum: ", res)
  res, _ = doubler(true)
  fmt.Println("true:", res)
  res, _ = doubler(float32(3.14))
  fmt.Println("3.14:", res)

}