curly-braces | 易学教程

std::array<T> initialization

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问题 A std::array<T> is essentially a C-style array wrapped in a struct . The initialization of struct s requires braces, and the initialization of arrays requires braces as well. So I need two pairs of braces: std::array<int, 5> a = {{1, 2, 3, 4, 5}}; But most of the example code I have seen only uses one pair of braces: std::array<int, 5> b = {1, 2, 3, 4, 5}; How come this is allowed, and does it have any benefits or drawbacks compared to the first approch? 回答1: The benefit is that you have ...

Extra brace brackets in C++ code

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问题 Sometimes you run into code that has extra brace brackets, that have nothing to do with scope, only are for readability and avoiding mistakes. For example: GetMutexLock( handle ) ; { // brace brackets "scope" the lock, // must close block / remember // to release the handle. // similar to C#'s lock construct } ReleaseMutexLock( handle ) ; Other places I have seen it are: glBegin( GL_TRIANGLES ) ; { glVertex3d( .. ) ; glVertex3d( .. ) ; glVertex3d( .. ) ; } // must remember to glEnd! glEnd() ;

Why do Java array declarations use curly brackets?

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问题 I would like to know why Java array declarations use curly brackets as opposed to the standard parenthesis. As illustrated here. I imagine this may take further understanding of curly brackets in general, but this specifically is on my agenda right now. Object[] tableHeaders = {"Cars","Trucks","Tacos"}; This is correct, as opposed to. Object[] tableHeaders = ("Cars","Trucks","Tacos"); 回答1: Curly brackets usually denotes sets and ensembles while parenthesis usually denotes parameters in C-like

C# Switch statement with/without curly brackets… what's the difference?

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问题 Has C# always permitted you to omit curly brackets inside a switch() statement between the case: statements? What is the effect of omitting them, as javascript programmers often do? Example: switch(x) { case OneWay: { // <---- Omit this entire line int y = 123; FindYou(ref y); break; } // <---- Omit this entire line case TheOther: { // <---- Omit this entire line double y = 456.7; // legal! GetchaGetcha(ref y); break; } // <---- Omit this entire line } 回答1: Curly braces are not required, but

What Is a Curly-Brace Enclosed List If Not an intializer_list?

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I asked a question here: Lifetime Extension of a initializer_list return involving the non-functional code: const auto foo = [](const auto& a, const auto& b, const auto& c) { return {a, b, c}; }; I believed the lambda was trying to return an intializer_list (that's bad, don't do that.) But I got a comment : It's not an initializer_list , it's an initializer list. Two different things. I just thought that any time you did a curly-braced list you were creating an intializer_list . If that's not what's happening, what is a list in curly-braces? There are three distinct, but related concepts here:

Curly Braces Notation in PHP

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I was reading source of OpenCart and I ran into such expression below. Could someone explain it to me: $quote = $this->{'model_shipping_' . $result['code']}->getQuote($shipping_address); In the statement, there is a weird code part that is $this->{'model_shipping_' . $result['code']} which has {} and I wonder what that is? It looks an object to me but I am not really sure. Curly braces are used to denote string or variable interpolation in PHP. It allows you to create 'variable functions', which can allow you to call a function without explicitly knowing what it actually is. Using this, you

What is the meaning of the ${0##…} syntax with variable, braces and hash character in bash?

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I just saw some code in bash that I didn't quite understand. Being the newbie bash scripter, I'm not sure what's going on. echo ${0##/*} echo ${0} I don't really see a difference in output in these two commands (prints the script name). Is that # just a comment? And what's with the /* . If it is a comment, how come it doesn't interfere with the closing } brace? Can anyone give me some insight into this syntax? Mark Byers See the section on Substring removal in the Advanced Bash-Scripting Guide‡: ${string#substring} Deletes shortest match of substring from front of $string . ${string##substring

Curly braces in “new” expression? (e.g. “new MyClass() { … }”)

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What do the curly braces do there ? handler1 = new Handler() { public void handleMessage() { } }; object = new Class_Name() {}; ? This syntax exists only on Android or Java also? And what is it called in Java? Thank for your helps. This is the syntax for creating an instance of anonymous class that extends Handler . This is part of Java. Bhavik Ambani This is happned when you create the instance reference of the Interface. For example I want to create the instance of the interface Runnable with the class, then I can create it by creating an anonymous class for the same and override the run()

What is the meaning of curly braces? [closed]

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问题 Just starting to figure Python out. I've read this question and its responses: Is it true that I can't use curly braces in Python? and I still can't fathom how curly braces work, especially since pages like Simple Programs: http://wiki.python.org/moin/SimplePrograms use curly braces all over the place. I understand square brackets and regular curved parentheses, but I don't know what's meant by "defining dictionaries" or what they're supposed to represent. 回答1: "Curly Braces" are used in

Do you use curly braces for additional scoping? [closed]

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I mean other than using it when required for functions, classes, if, while, switch, try-catch. I didn't know that it could be done like this until I saw this SO question . In the above link, Eli mentioned that "They use it to fold up their code in logical sections that don't fall into a function, class, loop, etc. that would usually be folded up." What other uses are there besides those mentioned? Is it a good idea to use curly braces to limit the scope of your variables and expand the scope only if required (working on a "need-to-access" basis)? Or is it actually silly? How about using scopes