decrement | 易学教程

What does “!--” do in JavaScript?

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问题 I have this piece of code (taken from this question): var walk = function(dir, done) { var results = []; fs.readdir(dir, function(err, list) { if (err) return done(err); var pending = list.length; if (!pending) return done(null, results); list.forEach(function(file) { file = path.resolve(dir, file); fs.stat(file, function(err, stat) { if (stat && stat.isDirectory()) { walk(file, function(err, res) { results = results.concat(res); if (!--pending) done(null, results); }); } else { results.push

Substraction or decrement random access iterator pointing to begin

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问题 Consider following piece of code void foo( bool forwad ) { vector<MyObject>::iterator it, end_it; int dir; it = some_global_vector.begin() + some_position; if( forward ) { dir = 1; it += 1; end_it = some_global_vector.end(); } else { dir = -1; it -= 1; end_it = some_global_vector.begin()-1; } while( it != end_it ) { if( do_domething() ) break; it += dir; } } As you can see there is some doubt when forward == false becouse there is an substraction from begin() and iterator it can be

pre Decrement vs. post Decrement

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问题 When should I use pre decrement and when to use post decrement? and for the following code snippet, should I use pre or post decrement. static private void function(int number) { charArr = new char[number]; int i = 0; int tempCounter; int j = 0; while(charrArr!=someCharArr) { tempCounter = number - 1; password[tempCounter] = element[i%element.Length]; i++; //This is the loop the I want to use the decrementing in. //Suppose I have a char array of size 5, the last element of index 5 is updated

Decrement index in a loop after Swift C-style loops deprecated

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How would you express a decrementing indexed loop in Swift 3.0, where the syntax below is not valid any more? for var index = 10 ; index > 0; index-=1{ print(index) } // 10 9 8 7 6 5 4 3 2 1 Here is an easier (and more Swifty) approach. for i in (0 ..< 5).reversed() { print(i) // 4,3,2,1,0 } let array = ["a", "b", "c", "d", "e"] for element in array.reversed() { print(element) // e,d,c,b,a } array.reversed().forEach { print($0) } // e,d,c,b,a print(Array(array.reversed())) // e,d,c,b,a Martin R C-style loops with a fixed increment or decrement can be replaced by stride() : for index in 10

Decrement index in a loop after Swift C-style loops deprecated

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问题 How would you express a decrementing indexed loop in Swift 3.0, where the syntax below is not valid any more? for var index = 10 ; index > 0; index-=1{ print(index) } // 10 9 8 7 6 5 4 3 2 1 回答1: Here is an easier (and more Swifty) approach. for i in (0 ..< 5).reversed() { print(i) // 4,3,2,1,0 } let array = ["a", "b", "c", "d", "e"] for element in array.reversed() { print(element) // e,d,c,b,a } array.reversed().forEach { print($0) } // e,d,c,b,a print(Array(array.reversed())) // e,d,c,b,a

The “++” and “--” operators have been deprecated Xcode 7.3

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问题 I am looking at Xcode 7.3 notes and I notice this issue. The ++ and -- operators have been deprecated Could some one explain why it is deprecated? And am I right that in new version of Xcode now you going to use instead of ++ this x += 1 ; Example: for var index = 0; index < 3; index += 1 { print(\"index is \\(index)\") } 回答1: A full explanation here from Chris Lattner, Swift's creator. I'll summarize the points: It's another function you have to learn while learning Swift Not much shorter