syntax

问题 I would like to know what the a.*, c.name, ... a.access etc means. In other words, what exactly am I referring to when I add a letter before the dot and the funciton of the dot. Here is an example of code where I found this occurrence: $query = "SELECT a.*, c.name as categoryname,c.id as categoryid, ". "c.alias as categoryalias, c.params as categoryparams". " FROM #__k2_items as a". " LEFT JOIN #__k2_categories c ON c.id = a.catid"; $query .= " WHERE a.published = 1" ." AND a.access <= {$aid}

问题 I have two javascript closures and I'm trying to understand why one will accept and input with a particular syntax and the other will reject. function multiply(factor) { var ace = (function(number) { return number*factor; }); return ace; } var yup = multiply(4); console.log(yup(5)); This outputs 20 to the console as it should. The second Closure I have is var k = 3; var add = (function () { console.log(k); var counter = k; return function (j) {counter += 1; return counter*j} })(k); add();

问题 The following code I wrote in JavaScript, but I'm trying to convert it into something Python can understand, specifically the for loop . I tried reading up on how the for loop syntax in Python reads, but I just can't seem to wrap my head around it, since it's very different to its equivalent in many popular web dev languages. Can someone explain to how it's written and how it work, preferably in simple terms. Thank you!! name = prompt("enter a name"); for (var i = 0; i < name.length; i++) {

问题 My goal is to have an AWS System Manager Document download a script from S3 and then run that script on the selected EC2 instance. In this case, it will be a Linux OS. According to AWS documentation for aws:downloadContent the sourceInfo Input is of type StringMap. The example code looks like this: { "schemaVersion": "2.2", "description": "aws:downloadContent", "parameters": { "sourceType": { "description": "(Required) The download source.", "type": "String" }, "sourceInfo": { "description":

问题 I want to regroup US states by regions and thus I need to define a "US state" -> "US Region" mapping function, which is done by setting up an appropriate data frame. The basis is this exercise (apparently this is a map of the "Commonwealth of the Fallout"): One starts off with an original list in raw form: Alabama = "Gulf" Arizona = "Four States" Arkansas = "Texas" California = "South West" Colorado = "Four States" Connecticut = "New England" Delaware = "Columbia" which eventually leads to

问题 I am migrating a Room database in my Android app. This is the migration code: static final Migration MIGRATION_1_2 = new Migration(1, 2) { @Override public void migrate(SupportSQLiteDatabase database) { database.execSQL("ALTER TABLE item RENAME itemInfoId TO itemId"); } }; The error message android.database.sqlite.SQLiteException: near "itemInfoId": syntax error (code 1 SQLITE_ERROR): , while compiling: ALTER TABLE item RENAME itemInfoId TO itemId I have also tried the SQL of "ALTER TABLE

问题 This question already has answers here : ES6 Array destructuring weirdness (4 answers) Closed 4 years ago . For the following fibonacci function, it works as expected: function fibonacci(n) { var nums = [] var a = b = 1 for (let i = 0; i < n; i++) { [a, b] = [b, a + b] nums.push(a) } return nums } console.log(fibonacci(5)); // outputs: [1,2,3,5,8] but after I changed two statements' order, it doesn't work: function fibonacci(n) { var nums = [] var a = b = 1 for (let i = 0; i < n; i++) { nums

问题 This question already has answers here : ES6 Array destructuring weirdness (4 answers) Closed 4 years ago . For the following fibonacci function, it works as expected: function fibonacci(n) { var nums = [] var a = b = 1 for (let i = 0; i < n; i++) { [a, b] = [b, a + b] nums.push(a) } return nums } console.log(fibonacci(5)); // outputs: [1,2,3,5,8] but after I changed two statements' order, it doesn't work: function fibonacci(n) { var nums = [] var a = b = 1 for (let i = 0; i < n; i++) { nums

问题 map and filter are often interchangeable with list comprehensions, but reduce is not so easily swapped out as map and filter (and besides, in some cases I still prefer the functional syntax anyway). When you need to operate on the arguments themselves, though, I find myself going through syntactical gymnastics and eventually have to write entire functions to maintain readability. I'll use map to keep the illustration unit-test simple, but please keep in mind that real-life use-cases might be

问题 Is there any expression possible for the syntax to include multiple headers at once, with no need to write the "#include"-expression for each file new? Like, for example: #include <stdio.h>, <stdlib.h>, <curses.h>, <string.h> /* Dummy-Expression 1. */ OR #include <stdio.h> <stdlib.h> <curses.h> <string.h> /* Dummy-Expression 2. */ Question is for C AND C++. 回答1: No, there is no way to do this. You have to type out (or copy) each #include to its own line, like this: #include <stdio.h> #include