variables

问题 Example code： fn main() { let a = [1, 2, 3, 4, 5]; reset(a); } fn reset(mut b: [u32; 5]) { b[0] = 5; } The variable a is an immutable array, and the reset function's parameter b is a mutable array; intuitively I need to modify a to a mutable array before I can call the reset method, but the compiler tells me that I don't need to do this, why is this? fn main() { let mut a = [1, 2, 3, 4, 5]; reset(a); } fn reset(mut b: [u32; 5]) { b[0] = 5; } warning: variable does not need to be mutable -->

问题 var date1 = new Date(); date1.setFullYear(2011, 6, 1); // 2011-07-01, ok console.log(date1); // set date2 the same date as date1 var date2 = date1; // ... // now I'm gonna set a new date for date2 date2.setFullYear(2011, 9, 8); // 2011-10-08, ok console.log(date2); // 2011-10-08, wrong, expecting 2011-07-01 // I didn't assign a new date to date1 // WHY is date1 changed? console.log(date1); 回答1: Date is object , so it is assigned as reference - simple approach is date2 = new Date( date1 ); 回答2

问题 var date1 = new Date(); date1.setFullYear(2011, 6, 1); // 2011-07-01, ok console.log(date1); // set date2 the same date as date1 var date2 = date1; // ... // now I'm gonna set a new date for date2 date2.setFullYear(2011, 9, 8); // 2011-10-08, ok console.log(date2); // 2011-10-08, wrong, expecting 2011-07-01 // I didn't assign a new date to date1 // WHY is date1 changed? console.log(date1); 回答1: Date is object , so it is assigned as reference - simple approach is date2 = new Date( date1 ); 回答2

问题 item =["Item_name","Price"] stop = input("Enter your message: ") if stop[:3] == "add": item2 = stop[4:] I have a code something like this and I want to get the variable item based on a user input. For example, the user types inputs "add item", it should output item[0] and item[1] , but I don't know how to do it. 回答1: Breaking it down into small pieces is the easiest way to keep it from getting out of hand when you need to add more commands -- trying to parse a command string with slices is

问题 I'm getting mad with the fact that a client could change cookie values, because I realized that everything on my website was pretty unsecure. Before I just setted a cookie with an expire time, and I was sure that a given user would have kept a particular property (such as "logged in" or "he has this privilege") for that exact amount of time (unless he cleared the cache). Now that I have to switch everything to sessions, which doesn't have an expire time. So, while for the login I implemented

问题 I'm building a basic cloud infrastructure management site and have a problem with the page that lists virtual machines. The flask app pulls a list that is generated via various cloud platform's APIs, and is in the below format: vm_list = { 'vmid': [], 'name': [], 'state': [], 'platform': [] } the list is populated by looping through the API output and appending each value like so: def zip_list(): ... for node in driver.list_nodes(): vm_list["vmid"].append(node.uuid) vm_list["name"].append

问题 If I have the following ordered list: <ol class="breadcrumbs"> <li title="Sbox"> <a href="myURL">SANDBOX</a> </li> <li title="API Ref"> <a href="myURL">API Reference</a> </li> <li title="Schemas"> <a href="myURL">Schema Files</a> </li> </ol> I am able to 'harvest' the second child list item's text ('API Reference') by using this jQuery code: var bcrumbtext = $("ol.breadcrumbs li:nth-child(2)").text(); If I then have multiple Unordered lists (6 to be exact) with the following structure: <ul

问题 If I have the following ordered list: <ol class="breadcrumbs"> <li title="Sbox"> <a href="myURL">SANDBOX</a> </li> <li title="API Ref"> <a href="myURL">API Reference</a> </li> <li title="Schemas"> <a href="myURL">Schema Files</a> </li> </ol> I am able to 'harvest' the second child list item's text ('API Reference') by using this jQuery code: var bcrumbtext = $("ol.breadcrumbs li:nth-child(2)").text(); If I then have multiple Unordered lists (6 to be exact) with the following structure: <ul

问题 I'm creating a class using java and it's a basic class to understand objects,methods etc.. anyways the class name is Student and it is supposed to assign a student ID to each newly created object. Student ID's start at 1000000 and increment by 1, so every new object should have the class assign a student ID, 10000001, 100000002 etc.. public class Student { private static long nextID=10000000; private long studentID; //etc.. public Student (String name, long studentID, int count, double total

问题 I am a beginner to shell programming and it sounds like a very stupid question but i cant seem to be able to increase the variable value by 1. I have looked at tutorial but it only shows how to add together 2 variables I have tried the following methods but it doesnt work i=0 $i=$i+1 # doesnt work , command not found echo "$i" $i='expr $i+1' # doesnt work , command not found echo "$i" $i++ # doesnt work , command not found echo "$i" How do i increment the value of a variable by 1?? 回答1: You