Question

我想在F＃中创建一个bitflags枚举，使用bitshift运算符来提高可读性：例如

[<Flags>]
type DaysOfWeek =
    | Monday = 1 <<< 0
    | Tuesday = 1 <<< 1
    | Wednesday = 1 <<< 2
    | Thursday = 1 <<< 3
    | Friday = 1 <<< 4
    | Saturday = 1 <<< 5
    | Sunday = 1 <<< 6

然而，F＃编译器不喜欢这个。它在成员定义中说＆＃34;意外的中缀运算符＆＃34;。

我希望这种方法超过两种手动权力。有没有办法说服编译器我不是邪恶的？

Answer 1

这不完全是您所要求的，但您可以使用0b前缀来编写二进制长手，例如：

[<Flags>]
type DaysOfWeek =
    | Monday    = 0b0000001
    | Tuesday   = 0b0000010
    | Wednesday = 0b0000100
    | Thursday  = 0b0001000
    | Friday    = 0b0010000
    | Saturday  = 0b0100000
    | Sunday    = 0b1000000

Answer 2

将案例与值分开的替代方法，更详细但更灵活：

<?php
/**
 * Created by PhpStorm.
 * User: Taz
 * Date: 9/29/2016
 * Time: 5:37 PM
 */
?>
<html>
<head>
    <title>Ajax Image Upload Using PHP and jQuery</title>
    <link rel="stylesheet" href="style.css" />
    <link href='http://fonts.googleapis.com/css?family=Roboto+Condensed|Open+Sans+Condensed:300' rel='stylesheet' type='text/css'>
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
    <script type="text/javascript">

        $(document).ready(function (e) {
            $("#uploadimage").on('submit',(function(e) {
                e.preventDefault();
                $("#message").empty();
                $('#loading').show();
                $.ajax({
                    url: "ajax_upload_image_submit.php", // Url to which the request is send
                    type: "POST",                       // Type of request to be send, called as method
                    data: new FormData(this),           // Data sent to server, a set of key/value pairs (i.e. form fields and values)
                    contentType: false,                 // The content type used when sending data to the server.
                    cache: false,                       // To unable request pages to be cached
                    processData:false,                  // To send DOMDocument or non processed data file it is set to false
                    success: function(data)             // A function to be called if request succeeds
                    {
                        $('#loading').hide();
                        $("#message").html(data);
                    }
                });
            }));

// Function to preview image after validation
            $(function() {
                $("#file").change(function() {
                    $("#message").empty(); // To remove the previous error message
                    var file = this.files[0];
                    var imagefile = file.type;
                    var match= ["image/jpeg","image/png","image/jpg"];
                    if(!((imagefile==match[0]) || (imagefile==match[1]) || (imagefile==match[2])))
                    {
                        $('#previewing').attr('src','noimage.png');
                        $("#message").html("<p id='error'>Please Select A valid Image File</p>"+"<h4>Note</h4>"+"<span id='error_message'>Only jpeg, jpg and png Images type allowed</span>");
                        return false;
                    }
                    else
                    {
                        var reader = new FileReader();
                        reader.onload = imageIsLoaded;
                        reader.readAsDataURL(this.files[0]);
                    }
                });
            });
            function imageIsLoaded(e) {
                $("#file").css("color","green");
                $('#image_preview').css("display", "block");
                $('#previewing').attr('src', e.target.result);
                $('#previewing').attr('width', '250px');
                $('#previewing').attr('height', '230px');
            };
        });


    </script>

    <style>


        body {
            font-family: 'Roboto Condensed', sans-serif;
        }
        h1
        {
            text-align: center;
            background-color: #96DAD1;
            height: 70px;
            color: rgb(95, 89, 89);
            margin: 0 0 -29px 0;
            padding-top: 14px;

            font-size: 35px;
        }
        .main {
            position: absolute;
            top: 50px;
            left: 20%;
            width: 450px;
            height:530px;
            border: 2px solid gray;

        }
        .main label{
            color: rgba(0, 0, 0, 0.71);
            margin-left: 60px;
        }
        #image_preview{
            position: absolute;
            font-size: 30px;
            top: 100px;
            left: 100px;
            width: 250px;
            height: 230px;
            text-align: center;
            line-height: 180px;
            font-weight: bold;
            color: #C0C0C0;
            background-color: #FFFFFF;
            overflow: auto;
        }
        #selectImage{
            padding: 19px 21px 14px 15px;
            position: absolute;
            bottom: 0px;
            width: 414px;
            background-color: #EDFCFF;

        }
        .submit{
            font-size: 16px;
            background: linear-gradient(#ffbc00 5%, #ffdd7f 100%);
            border: 1px solid #e5a900;
            color: #4E4D4B;
            font-weight: bold;
            cursor: pointer;
            width: 300px;
            border-radius: 5px;
            padding: 10px 0;
            outline: none;
            margin-top: 20px;
            margin-left: 15%;
        }
        .submit:hover{
            background: linear-gradient(#ffdd7f 5%, #ffbc00 100%);
        }
        #file {
            color: red;
            padding: 5px;
            border: 5px solid #96DAD1;
            background-color: #96DAD1;
            margin-top: 10px;


            margin-left: 15%;
            width: 72%;
        }
        #message{
            position:absolute;
            top:120px;
            left:815px;
        }
        #success
        {
            color:green;
        }
        #invalid
        {
            color:red;
        }
        #line
        {
            margin-top: 274px;
        }
        #error
        {
            color:red;
        }
        #error_message
        {
            color:blue;
        }
        #loading
        {
            display:none;
            position:absolute;
            top:50px;
            left:850px;
            font-size:25px;
        }



    </style>





</head>
<body>
<div class="main">
    <h1>Facebook Update</h1><br/>
    <hr>
    <form id="uploadimage" action="" method="post" enctype="multipart/form-data">
        <div id="image_preview"><img id="previewing" src="noimage.png" width="250" height="230" /></div>
        <hr id="line">
        <div id="selectImage">


            <label>Select Your Image</label><br/>
            <input type="file" name="file" id="file" required />

            <label>FB Link</label><br/>
            <input type="text" name="fb_link" id="fb_link" required />




            <label>Show/Hide Status</label><br/>
            <select name="show_fb" class="myselect" required>
                <option value="">---Select---</option>
                <option value="1">Show</option>
                <option value="0">Hide</option>
            </select>




            <input type="submit" value="Upload" class="submit" />
        </div>
    </form>
</div>
<h4 id='loading' >loading..</h4>
<div id="message"></div>
</body>
</html>

Answer 3

这是 Dave Fancher 在 The Book of F#

中推荐的方法

将 Flags 属性与值为 2 的幂的值一起使用：

open System

[<Flags>]    
type DayOfWeek =
  | None = 0
  | Sunday = 1
  | Monday = 2
  | Tuesday = 4
  | Wednesday = 8
  | Thursday = 16
  | Friday = 32
  | Saturday = 64

Flags 属性不是必需的，但可以明确您的意图。

您现在可以使用按位运算符表示值的组合：

let weekend = DayOfWeek.Saturday ||| DayOfWeek.Sunday

F＃位标志枚举

3 个答案: