reference

问题 Let's consider the following code: class a { public $var1; function disp(){ echo $this->var1; } } $obj1 = new a; echo '<br/>After instantiation into $obj1:<br/>'; xdebug_debug_zval('obj1'); $obj1->var1 = "Hello "; echo '<br/><br/>After assigning "Hello" to $obj->var1:<br/>'; $obj1->disp(); echo "<br/><br/>"; xdebug_debug_zval('obj1'); The output: After instantiation into $obj1: obj1: (refcount=1, is_ref=0)=class a { public $var1 = (refcount=2, is_ref=0)=NULL } After assigning "Hello" to $obj-

问题 I'm trying to wrap my head around the basic concepts of the R programming language and am finding it difficult since R is geared towards statistics instead of general-purpose programming. I can't find anything similar to pointers/references. How would you implement a linked list, search tree, etc. within the R language? Note: I understand that if you're actually rolling your own self-referential data structures in R, there's probably a better way to accomplish what you're trying to accomplish

问题 I work on a medium sized development team that maintains a 8+ years old web application written in Java 1.4. For new development I always try to convince people to adhere to newer standards and best practices, That goes from simple things like using new naming standards like HtmlImplementation over HTMLImplementation, to things like why it's better to code against an interface versus coding against concrete classes, favor immutability or object composition a over class inheritance. I have

问题 In Objective C you can define a property as having a strong or weak reference like so: @property(strong)... @property(weak)... How is this done in swift? 回答1: Straight from the Swift Language guide: class Person { let name: String init(name: String) { self.name = name } var apartment: Apartment? deinit { println("\(name) is being deinitialized") } } class Apartment { let number: Int init(number: Int) { self.number = number } weak var tenant: Person? deinit { println("Apartment #\(number) is

问题 I'm trying to send value into function using reference pointer but it gave me a completely non-obvious error to me #include "stdafx.h" #include <iostream> using namespace std; void test(float *&x){ *x = 1000; } int main(){ float nKByte = 100.0; test(&nKByte); cout << nKByte << " megabytes" << endl; cin.get(); } Error : initial value of reference to non-const must be an lvalue I have no idea what I must do to repair above code, can someone give me some ideas on how to fix that code? thanks :)

问题 Being new to Rails, I am having a difficult time finding a website or reference that gives a run down summary of Ruby on Rails. I understand MVC, ActiveRecord, and that sort of stuff on a basic level, but I am having a hard time understanding some of the relationships and fundamentals. For instance: What are all naming conventions I need to be aware of? How should controller actions be structured and named? What are the best ways to render information in a view (via :content_for or render a

问题 Being new to Rails, I am having a difficult time finding a website or reference that gives a run down summary of Ruby on Rails. I understand MVC, ActiveRecord, and that sort of stuff on a basic level, but I am having a hard time understanding some of the relationships and fundamentals. For instance: What are all naming conventions I need to be aware of? How should controller actions be structured and named? What are the best ways to render information in a view (via :content_for or render a

问题 I have noticed that there are times when coding in Java that I have seen fields called by method: System.out.println(object.field); and by class: System.out.println(Class.field); I have not seen any clear distinguishing in my textbooks about what the semantics are for these two cases, and I fear that it is going to be, at least for a noob, a subtle point. My intuition is that the class calling will be used for static fields? Thanks guys. So much con'foo'sion. 回答1: The field Class.field can be

问题 I have a cell range that I named "cell_range" in Excel. I want to extract the fourth row and fifth column from this table. The formula, =vlookup(4,cell_range,5) gives me the value I am looking for. However, I also have the text "cell_range" in cell A1. Instead of typing out "cell_range" in my formula, I want to reference "cell_range" indirectly by referencing cell A1. The formula vlookup(4,A1,5) is giving me a "#N/A" error. How can I indirectly reference the table "cell_range" in my formula?

问题 Let's say I have class that contains a lot of fields and I want to make initializer that work for all fields so that I don't need to write an initializer for each of them. class Foo(): def __init__(n): self.n = n self.x = None self.m = None self.v = None but method def init_x(self, x): # initialize or erase x to zeros x = np.zeros(self.n) doesn't work because x= loses reference to x . But @staticmethod def get_x(x, i): return x[i] @staticmethod def set_x(x, i): x[i] = val works. What could