syntax

问题 Let's say I have the following code: <?php echo "<div id=\"root\">"; echo "<div id=\"child_of_root\">"; echo "<img src=\"picture1.png\">"; echo "<img src=\"picture2.png\">"; echo "<img src=\"picture3.png\">"; echo "<img src=\"picture4.png\">"; echo "<img src=\"picture5.png\">"; echo "</div>"; echo "</div>"; ?> If I ran this the following HTML would be rendered all inline without any line breaks: <div id="root"><div id="child_of_root"><img src="picture1.png"><img src="picture2.png"><img src=

问题 CMake's if s go like this: if (condition) ... else if (...) ... else (...) ... endif (...) With else if (...) the (...) tests for a separate condition. Why else (...) and not just else ? Why endif (...) and not endif ? Cmake's functions go like this: function(funcname ...) ... endfunction(funcname ...) Why endfunction(funcname ...) and not simply endfunction ? I can omit the contents of the redundant parenthesis where they appear, like so: endif () . What's the purpose of this construct? 回答1:

问题 I asked this question, and it turned out that when removing an attribute from an element, checking whether the element exists first using elem.xxx!==undefined makes the runtime faster. Proof. Why is it quicker? There's more code to go through and you'll have to encounter the removeAttribute() method whichever way you go about this. 回答1: Well, first thing you need to know is that elem.xxx is not the same as elem.getAttribute() or any other method relative to the attribute. elem.xxx is a

问题 I have a class with member variables. What is the syntax in PHP to access the member variables from within the class when the class is being called from a static context? Basically I want to call a class method (but not create a new object), but when the class method is called, I want a handful of static constant variables to be initialized that need to be shared among the different class methods. OR if there's a better way to do it then what I'm proposing, please share with me (I'm new to

问题 I have a class with member variables. What is the syntax in PHP to access the member variables from within the class when the class is being called from a static context? Basically I want to call a class method (but not create a new object), but when the class method is called, I want a handful of static constant variables to be initialized that need to be shared among the different class methods. OR if there's a better way to do it then what I'm proposing, please share with me (I'm new to

问题 I'm trying to define a block that takes a block as an argument. What's wrong with the following line of code? id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^)(void)block) { NSObject *item = nil; block(); return item; }; Why does the compiler keep giving errors like Parameter name omitted and Expected ")" ? 回答1: id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^block)(void)) { NSObject *item = nil; block(); return item; }; Blocks have similar syntax to

问题 I'm trying to define a block that takes a block as an argument. What's wrong with the following line of code? id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^)(void)block) { NSObject *item = nil; block(); return item; }; Why does the compiler keep giving errors like Parameter name omitted and Expected ")" ? 回答1: id (^cacheResult)(NSString *, id(^)(void)) = ^(NSString *name, id(^block)(void)) { NSObject *item = nil; block(); return item; }; Blocks have similar syntax to

问题 In order to make my code easier to read, I am using type aliases in Swift for various types of closures. I have the following basic set of closures: public typealias FailureClosure = (error: NSError?) -> Void public typealias ProgressClosure = (progress: Float32) -> Void public typealias BasicClosure = () -> Void I would like to add a closure typealias that supports generic arrays, but I can't seem to figure out the syntax for it. This is as far as I am able to get, but I get the compile time

问题 In F# I can't live without pipes ( <| and |> ) let console(dashboard : Dashboard ref) = let rec eat (command : string) = command.Split(' ','(',')') |> Seq.filter(fun s -> s.Length <> 0) |> fun C -> (Seq.head C).ToUpper() |> fun head -> Can I use <| and |> in OCaml? 回答1: These are available since OCaml 4.01. However, <| is named @@ there, so it has the correct operator associativity. Alternatively, you can either define them yourself: let (|>) v f = f v let (<|) f v = f v (* or: *) let (@@) f

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Which type of quotes we should use in css background url (“…”)? Single, double or no quote needed? Simple question. What quotation marks should I use in CSS? Option #1: background: url( 'foo.png' ); Option #2: background: url( "foo.png" ); Both works on "normal browsers". I just want to follow the standards. 回答1: The standards say: The format of a URI value is 'url(' followed by optional white space followed by