parentheses

问题 I have fed the following code through a static analysis tool: u1 = (u1 ^ u2); // OK u1 = (u1 ^ u2) & u3; // NOT OK u1 = (u1 ^ u2) & 10; // NOT OK u1 = (u1 ^ u2) & 10U; // NOT OK u1 = (unsigned char)(u1 ^ u2) & 10U; // OK u1 = (unsigned char)(u1 ^ u2) & u3; // OK "OK" means the static analysis tool did not complain. "NOT OK" means the static analysis tool did complain -- claiming that some operand of a bitwise operation is not an unsigned integer. The results from the last 2 lines show that

问题 I have an Angular 5 application with a series of components. Some of the components are children of others, and some are not. I would like the application to have a structure such as: */my-account/overview // homepage */my-account/my-stuff */profile */non-default I have a DefaultComponent that contains some generic elements such as site navigation that I would like to be present on most of the pages (everything except for the */non-default route/component). My routing module defines the

问题 The code: int r=1; System.out.println(r + (r=2)); The output is: 3. But I expected 4 because I thought the code inside the parentheses is executed first? 回答1: Official Docs on Operators says All binary operators except for the assignment operators are evaluated from left to right; assignment operators are evaluated right to left. So + is evaluated left-to-right ,where as assignment operators are evaluated right to left. 回答2: Use this if you want 4 int r=1; System.out.println((r=2) + r); //

问题 I've come across some code that surrounds the return value from a method/function in parentheses. What does that do? The code I saw took an image, resized it and then returned it. - (UIImage *)resizeImage:(UIImage *)image { // // some fascinating, but irrelevant, resizing code here // return (image); } 回答1: At least as far as C is concerned, it makes no difference. The parens aren't necessary, but they don't change the meaning of the return statement. The grammar of the return statement is

问题 I have some big messy SQL procedures that I'm debugging, and they tend to have a lot of heavily nested parentheses: SELECT * FROM (SELECT F1,F2 FROM TABLE1 AS X LEFT JOIN (SELECT F9,F8 FROM (SELECT F13,F14 FROM TABLE4) AS J INNER JOIN TABLE3 ON...) AS B ON X.F1=B.F9) AS X1 I'm looking for an editor that can automatically mark and optionally collapse/fold each parentheses set to ease reading, e.g. SELECT * FROM ... AS X1 SELECT * FROM (SELECT F1,F2 FROM TABLE1 AS X LEFT JOIN ... AS B ON X.F1=B

问题 I often find myself doing things like: println(foo) when I'd like to do: println foo The compiler does not allow this. Also, println is a mouthful, I really just want to say: echo foo So, in a base package object I created the echo version of println: def echo(x: Any) = Console.println(x) Easy enough, have echo application wide, great. Now, how do I invoke echo without needing to wrap the Any to print in parens? 回答1: object ∊ {def cho(s: Any) {println(s)}} ∊cho "Hello world" will save your

问题 I want to determine if a list contains a certain string, so I use a generator expression, like so: g = (s for s in myList if s == myString) any(g) Of course I want to inline this, so I do: any((s for s in myList if s == myString)) Then I think it would look nicer with single parens, so I try: any(s for s in myList if s == myString) not really expecting it work. Surprise! it does! So is this legal Python or just something my implementation allows? If it's legal, what is the general rule here?

问题 I want to determine if a list contains a certain string, so I use a generator expression, like so: g = (s for s in myList if s == myString) any(g) Of course I want to inline this, so I do: any((s for s in myList if s == myString)) Then I think it would look nicer with single parens, so I try: any(s for s in myList if s == myString) not really expecting it work. Surprise! it does! So is this legal Python or just something my implementation allows? If it's legal, what is the general rule here?

问题 I want to determine if a list contains a certain string, so I use a generator expression, like so: g = (s for s in myList if s == myString) any(g) Of course I want to inline this, so I do: any((s for s in myList if s == myString)) Then I think it would look nicer with single parens, so I try: any(s for s in myList if s == myString) not really expecting it work. Surprise! it does! So is this legal Python or just something my implementation allows? If it's legal, what is the general rule here?

问题 I know the difference in purpose between parentheses () and curly braces {} when grouping commands in bash. But why does the curly brace construct require a semicolon after the last command, whereas for the parentheses construct, the semicolon is optional? $ while false; do ( echo "Hello"; echo "Goodbye"; ); done $ while false; do ( echo "Hello"; echo "Goodbye" ); done $ while false; do { echo "Hello"; echo "Goodbye"; }; done $ while false; do { echo "Hello"; echo "Goodbye" }; done bash: