primitive-types

问题 Suppose I have a custom type wrapping an existing type, newtype T = T Int deriving Show and suppose I want to be able to add up T s, and that adding them up should result in adding the wrapped values up; I would do this via instance Num T where (T t1) + (T t2) = T (t1 + t2) -- all other Num's methods = undefined I think we are good so far. Please, tell me if there are major concerns up to this point. Now let's suppose that I want to be able to multiply a T by an Int and that the result should

问题 Suppose I have a custom type wrapping an existing type, newtype T = T Int deriving Show and suppose I want to be able to add up T s, and that adding them up should result in adding the wrapped values up; I would do this via instance Num T where (T t1) + (T t2) = T (t1 + t2) -- all other Num's methods = undefined I think we are good so far. Please, tell me if there are major concerns up to this point. Now let's suppose that I want to be able to multiply a T by an Int and that the result should

问题 Suppose I have a custom type wrapping an existing type, newtype T = T Int deriving Show and suppose I want to be able to add up T s, and that adding them up should result in adding the wrapped values up; I would do this via instance Num T where (T t1) + (T t2) = T (t1 + t2) -- all other Num's methods = undefined I think we are good so far. Please, tell me if there are major concerns up to this point. Now let's suppose that I want to be able to multiply a T by an Int and that the result should

问题 I am trying to use Python term to explain why the following happens, can somebody explain why tmp becomes to [[1,2,3]] not stay as [[1,2]] ? arr = [] tmp = [1,2] arr.append(tmp) print arr # [[1,2]] tmp.append(3) print arr # [[1,2,3]] 回答1: arr = [] is an empty list, and when you append tmp to it via: tmp = [1, 2] arr.append(tmp) You are putting tmp in the arr list, thus giving you arr = [tmp] which can be expanded to arr = [[1,2]] . But the neat thing here is that you maintain a reference to

问题 I am trying to use Python term to explain why the following happens, can somebody explain why tmp becomes to [[1,2,3]] not stay as [[1,2]] ? arr = [] tmp = [1,2] arr.append(tmp) print arr # [[1,2]] tmp.append(3) print arr # [[1,2,3]] 回答1: arr = [] is an empty list, and when you append tmp to it via: tmp = [1, 2] arr.append(tmp) You are putting tmp in the arr list, thus giving you arr = [tmp] which can be expanded to arr = [[1,2]] . But the neat thing here is that you maintain a reference to

问题 Does Kotlin have primitive types?. When I declare the variable: val myAge: Int = 18 then the myAge variable stores the actual values is 18 or stores the addresses of the objects in the memory?. If Int is primitive type then why we can use its method like myAge.minus(10) ? 回答1: No... and yes. Kotlin doesn't have primitive type (I mean you cannot declare primitive directly). It uses classes like Int , Float as an object wrapper for primitives. When kotlin code is converted to jvm code, whenever

问题 Alright, I've been programming in Java for the better part of three years, now, and consider myself very experienced. However, while looking over the Java SE source code, I ran into something I didn't expect: in class Double : public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308 public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324 I did not expect this and can't find out what it means. If you don't know, I'm referring to the p and P that are

问题 How can i convert a string to a abstract number, provided string is any valid number in java (say int, long, double etc). I will not know the type of number in the string, so i can't use specific primitive parsing (like Integer.parseInt, Long.parseLong etc). Is there any generic way to convert it? Eg: String -> Number "23423" -> 23423 "34.3" -> 34.3 "45364573747546" -> 45364573747546 回答1: Use NumberFormat. Number cannot be instantiated because it is an abstract class. Number number =

问题 my understanding is that primitive types ( uint, string, Number, etc. ) of a class do not need to be set to null for garbage collection. for example, i am not required to write this dispose() method in the following class: package { //Imports import flash.display.Shape; //Class public class DrawSquare extends Shape { //Properties private var squareColorProperty:uint; //Constructor public function DrawSquare(squareColor:uint) { squareColorProperty = squareColor; init(); } //Initialize private

问题 my understanding is that primitive types ( uint, string, Number, etc. ) of a class do not need to be set to null for garbage collection. for example, i am not required to write this dispose() method in the following class: package { //Imports import flash.display.Shape; //Class public class DrawSquare extends Shape { //Properties private var squareColorProperty:uint; //Constructor public function DrawSquare(squareColor:uint) { squareColorProperty = squareColor; init(); } //Initialize private