array

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: #include #include #include #include #include using std::ifstream; using namespace std; int main (void) { int count=0; float sum=0; float maximum=-1000000; float sumOfX; float sumOfY; int size; int negativeY=0; int positiveX=0; int negativeX=0; ifstream points; //the points to be imported from file //points.open( "data.dat"); //points>>size; //cout>(x[count][0]); //cout>(x[count][1]); //cout This program is giving me expected constant expression error on the line where I declare float x[size][2]. Why? 回答1: float x[size][2]; That doesn't work

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I'm writing a c++ extension to v8, and want to pass an Array object into it. I see the incoming argument can be tested by IsArray(), but there isn't a ToArray(). How do you get access to its Length, and request elements by numeric index? Handle < Value > MyExtension ( const Arguments & args ) { Handle < Value > v = args [ 0 ]; if ( v -> IsArray ()) { // convert to array, find its length, and access its members by index... ? } ... } Must be missing something obvious here. Object can return all its properties, but that's not quite

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: This question already has an answer here: Undefined values in Array(len) initializer 4 answers I am confused by the results of map ping over an array created with new : function returnsFourteen() { return 14; } var a = new Array(4); > [undefined x 4] in Chrome, [, , , ,] in Firefox a.map(returnsFourteen); > [undefined x 4] in Chrome, [, , , ,] in Firefox var b = [undefined, undefined, undefined, undefined]; > [undefined, undefined, undefined, undefined] b.map(returnsFourteen); > [14, 14, 14, 14] I expected a.map(returnsFourteen) to return

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Before Java 8, lambda functionality could be achieved by using anonymous inner classes. For example: interface Lambda { void doStuff(); } // ... public void doWithCallback(Lambda callback) { // ... callback.doStuff(); } // ... doWithCallback(new Lambda { public void doStuff() { // ... } }); In terms of performance, is there a difference between still using this approach and using the new Java 8 lambdas? 回答1: Oracle has posted a study comparing performance between Lambdas and anonymous classes See JDK 8: Lambda Performance Study by Sergey

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have an array of strings, and want to make a hash out of it. Each element of the array will be the key, and I want to make the value being computed from that key. Is there a Ruby way of doing this? For example: ['a','b'] to convert to {'a'=>'A','b'=>'B'} 回答1: You can: a = ['a', 'b'] Hash[a.map {|v| [v,v.upcase]}] 回答2: %w{a b c}.reduce({}){|a,v| a[v] = v.upcase; a} 回答3: Here's a naive and simple solution that converts the current character to a symbol to be used as the key. And just for fun it capitalizes the value. :) h = Hash.new ['a', 'b

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I've come across the following signature double(&rotate_vec(double(&val)[4]))[4]; In the comments it "claims" to accept and return an array of four elements . My first reaction was that this does not even look standard c++ yet this compiles : double(&rotate_vec(double(&val)[4]))[4] { // ... return val; } int main() { double ar[4] = { 1, 2, 3, 5 }; rotate_vec(ar); return 0; } How is this c++ ? How would you read it ? We can't return an array from a function , just pointers, or can we ? 回答1: With C++03 the best you can do to simplify the

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Trying to create a MongoDB data source with icCube . The idea is to return the size of an array as a new field. Something like : $project: { "people": 1, "Count myFieldArray" : {$size : "$myFieldArray" } } But I'm getting for some records the following error : The argument to $size must be an Array, but was of type: EOO Is there a way that size is 0 if the field is empty or not an array (getting rid of the error) ? 回答1: You can use the $ifNull operator here. It seems the field is either not an array or not present by the given error: { "

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: While reading Effective Java I came across the suggestion to "use enums instead of int constants". In a current project I am doing something similar to that below: int COL_NAME = 0; int COL_SURNAME = 1; table[COL_NAME] = "JONES" How would I use enums instead to achieve this? Due to the interface I'm forced to use, I must use an int for my index. The example above is just an example. I'm actually using an API that takes an int for index values. 回答1: Applying one usefull pattern together with an anti-pattern often fails ;-) In your case using

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Is there a way to specify a one dimensional array in a ini file. so in my ini I would like to do someproperty = [array of something] I am using Zend_Config_Ini config adapter (I prefer ini for base configuration). 回答1: someproperty[] = a someproperty[] = b someproperty[] = c someproperty[] = d someproperty[] = e see: http://us.php.net/manual/en/function.parse-ini-file.php#75983 回答2: Although undocumented, this seems to work quite well too: foo[bar] = 5 foo[baz] = 6 hello[world] = 7 回答3: You can use separators to make further sub-sections,

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm trying to make a simple loop: const parent = this.el.parentElement console.log(parent.children) parent.children.forEach(child => { console.log(child) }) But I get the following error: VM384:53 Uncaught TypeError: parent.children.forEach is not a function Even though parent.children logs: What could be the problem? Note: Here's a JSFiddle . 回答1: The parent.children is an Array like object. Use the following solution: const parent = this.el.parentElement; console.log(parent.children); Array.prototype.forEach.call(parent.children, child =>