假设foo是一个采用容器类型的模板，它本身有一个模板参数来指定其值的类型：
template <template<typename val_t> class container_t>
struct foo;
为方便起见，foo将std::vector作为默认容器。麻烦的是，正式std::vector正式有两个参数，其中第二个参数有默认值。这意味着... container = std::vector不起作用。
使用C ++ 11的解决方案是定义模板别名：
template<typename val_t> using vec_dummy = std::vector<val_t>;
template <template<typename val_t> class container_t = vec_dummy>
struct foo;
我不喜欢，为了便于阅读（你必须搜索vec_dummy），而且出于审美原因（没有理由说明这种类型）。
有没有办法以某种方式匿名定义模板别名？其他解决问题的方法当然也受到热烈欢迎。
PS：实际上，foo使用内部数据类型作为提供容器的值类型，因此
template <typename container_t = std::vector<int>> struct foo;
不是一种选择。
答案 0 :(得分：3)
您可以使<?php
require('help.php');
if(isset($_POST['submit'])){
$title = $_POST['title'];
$content = $_POST['content'];
$posted = $_POST['posted'];
$date = date("Y-m-d H:i:s");
$ip = $_SERVER["REMOTE_ADDR"];
$rand = rand(1,1000000);
if(empty($title)){
echo "Titulli eshte bosh.";
}else if(empty($content)){
echo "Permbajtja eshte bosh.";
}else if(empty($_FILES['file']['name'])){
echo "Imazhi eshte bosh.";
}else if($_FILES['file']['name']){
$name = htmlspecialchars($_FILES['file']['name']);
$ext = end((explode(".", $name)));
$ext = strtolower($ext);
//if no errors...
if(!$_FILES['file']['error']){
//now is the time to modify the future file name and validate the file
$new_file_name = date('ymdHisu'). ".". $ext;
if($_FILES['file']['size'] > (6144000)){
$valid_file = false;
echo 'Oops! Your file\'s size is to large.';
}
elseif($ext !== "jpg" && $ext !== "png" && $ext !== "jpeg" && $ext != "gif" && $ext !== "bmp") {
$valid_file = false;
echo "Your file must be in jpg, jpeg, png, gif, or bmp formats.";
}else{
$valid_file = true;
}
//if the file has passed the test
if($valid_file){
//move it to where we want it to be
move_uploaded_file($_FILES['file']['tmp_name'], 'images/'.$new_file_name);
$exif_read = exif_read_data("images/".$new_file_name);
if(!empty($exif_read['Orientation'])){
$orientation_data = exif_read_data("images/".$new_file_name)['Orientation'];
}
if(isset($orientation_data) && $orientation_data !== 1){
$path = "images/". $new_file_name;
$buffer = ImageCreateFromJPEG($path);
$exif = exif_read_data($path);
if(!empty($exif['Orientation'])){
switch($exif['Orientation']){
case 8:
$buffer = imagerotate($buffer,90,0);
break;
case 3:
$buffer = imagerotate($buffer,180,0);
break;
case 6:
$buffer = imagerotate($buffer,-90,0);
break;
}
$image = imagejpeg($buffer, $path, 90);
}
}
if(empty($posted)){
$posted = 'Anonim';
}
$sql = "INSERT INTO problems(title, content, date, image, posted, ip) VALUES (:title, :content, :date, :image, :posted, :ip)";
$query = $db->prepare($sql);
$results = $query->execute(array(
':title' => htmlentities ($title),
':content' => htmlentities ($content),
':date' => $date,
':image' => $path,
':posted' => htmlentities ($posted),
':ip' => $ip
));
echo "<div id='ok'>Lajmi u raportua me sukses. Kontrollojeni <a href='index.php'>ketu</a> .</div>";
}
}else{
//set that to be the returned message
echo 'Ooops! Your upload triggered the following error: '.$_FILES['file']['error'];
}
}
}
?>
成为可变参数模板模板参数（颤抖）。
container_t这样您可以专注于值类型，但仍然保留任何分配器模板参数等。