Golang程序中的随机函数和持久性

Question

My program is below:

What I'm trying to do is see if there is a way to create a random function or use a built in function that is able to use know what food in this program was selected from the random selection and have it not used again for another week? I currently have foods set from 1-6 but I want to make sure the same food for example 2 isn't selected twice in a row for a week. Also I want the program to be able to possibly write what the last item that was selected so it won't choose it again for atleast a week. Would i be able to accomplish this with a simple text file that can be read from?

package main

import (
    "fmt"
    "math/rand"
    "time"
)

type Recipe struct { //Struct for recipe information
    name        string
    prepTime    int
    cookTime    int
    Ingredients []string //this is now a slice that will accept multiple elements
    ID          int
    Yield       int
}

func main() {
    var recipe1 Recipe //Declare recipe1 of Type Recipe
    var recipe2 Recipe
    var recipe3 Recipe

    /* recipe1 specifications */
    recipe1.name = "BBQ Pulled Chicken"
    recipe1.prepTime = 25
    recipe1.cookTime = 5
    recipe1.Ingredients = append(
        recipe1.Ingredients,
        "1 8-ounce can reduced-sodium tomato sauce",
    )
    recipe1.Ingredients = append(
        recipe1.Ingredients,
        "1/2 medium onion (grated),",
    )
    recipe1.ID = 1
    recipe1.Yield = 8

    /* Recipe 2 specifications */

    recipe2.name = "Steak Tacos with Pineapple"
    recipe2.prepTime = 45
    recipe2.cookTime = 45
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "3 tablespoons soy sauce,",
    )
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "1 tablespoon finely grated garlic,",
    )
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "1 tablespoon finely grated peeled fresh ginger,",
    )
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "1 1/2 pounds skirt steak, cut into 5-inch lengths,",
    )
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "Salt",
    )
    recipe2.Ingredients = append(
        recipe2.Ingredients,
        "Pepper",
    )
    recipe2.ID = 2
    recipe2.Yield = 4

    recipe3.name = "Simple Lemon Herb Chicken"
    recipe3.prepTime = 10
    recipe3.cookTime = 15
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "2 skinless boneless chicken breast halves,",
    )
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "1 Lemon,",
    )
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "Salt and Pepper to taste,",
    )
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "1 tablespoon olive oil,",
    )
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "2 sprigs fresh parsley (for garnish),",
    )
    recipe3.Ingredients = append(
        recipe3.Ingredients,
        "1 pinch dried oregano,",
    )
    recipe3.ID = 3
    recipe3.Yield = 2

    //call to printRecipe function below
    printRecipe(recipe1)
    totalTime(recipe1)
    printRecipe(recipe2)
    totalTime(recipe2)
    printRecipe(recipe3)
    totalTime(recipe3)

    //choose random number for recipe
    rand.Seed(time.Now().UTC().UnixNano())
    myrand := random(1, 6)
    fmt.Println(myrand)

    //logic for recipe to choose
    if myrand == 1 {
        fmt.Println(1)
        printRecipeOfTheDay(recipe1)
    } else if myrand == 2 {
        fmt.Println(2)
        printRecipeOfTheDay(recipe2)
    } else if myrand == 3 {
        fmt.Println(3)
        printRecipeOfTheDay(recipe3)
    } else if myrand == 4 {
        fmt.Println(4)
    }
}

//function to print Recipe
func printRecipe(recipe Recipe) {
    fmt.Printf("Recipe Name : %s
", recipe.name)
    fmt.Printf("Prep Time : %d
", recipe.prepTime)
    fmt.Printf("Cook Time : %d
", recipe.cookTime)
    fmt.Printf("Ingredients : %s
", recipe.Ingredients)
    fmt.Printf("Recipe ID : %d
", recipe.ID)
}

//random number function
func random(min, max int) int {
    return rand.Intn(max-min) + min
}

//function to print the winner for recipe of the day to use
//for either lunch or dinner
func printRecipeOfTheDay(recipe Recipe) {
    fmt.Printf("The recipe of the day is : %s
", recipe.name)
}

//Returns total time by addings cookTime and prepTime
func totalTime(recipe Recipe) {
    fmt.Printf("The total time for this recipe is %d
", recipe.cookTime+recipe.prepTime)
}

Answer 1

As @Volker said Perm is likely what you want to use. Here's an example that will generate the pseudo random list for you. You could just save that to a file json encoded. Then if you had 7 recipes you could use time.Weekday to grab a recipe number from the slice using the day of the week as key to the slice. Once you hit some pre-determined day just regenerate the slice and save.

package main

import "fmt"
import "math/rand"
import "time"

func main() {

  r := rand.New(rand.NewSource(time.Now().UnixNano()))
  i := r.Perm(6)
  fmt.Printf("%v
", i)
}