variable-assignment

问题 I have some data structures, and I would like to use one as a temporary, and another as not temporary. ArrayList<Object> myObject = new ArrayList<Object>(); ArrayList<Object> myTempObject = new ArrayList<Object>(); //fill myTempObject here .... //make myObject contain the same values as myTempObject myObject = myTempObject; //free up memory by clearing myTempObject myTempObject.clear(); now the problem with this of course is that myObject is really just pointing to myTempObject , and so once

问题 I have some data structures, and I would like to use one as a temporary, and another as not temporary. ArrayList<Object> myObject = new ArrayList<Object>(); ArrayList<Object> myTempObject = new ArrayList<Object>(); //fill myTempObject here .... //make myObject contain the same values as myTempObject myObject = myTempObject; //free up memory by clearing myTempObject myTempObject.clear(); now the problem with this of course is that myObject is really just pointing to myTempObject , and so once

问题 class abc { public: int x; }; abc b1; b1.x=10; int main() { } why can't we write this b1.x=10; outside of the main function? it shows error if we write b1.x=10; outside of the main function, why? 回答1: Because, b1.x=10; is an assignment statement which cannot be present at file scope . You can, however, use initialzation to provide the initial values. Something like abc b1 = {10}; 回答2: What you're doing is an assignment to a variable. That can't be done outside of a function. What you can do

问题 Is there a way to make my new Class mimic the behavior of an int or any Valuetype? I want something, so these assignments are valid MyClass myClass = 1; int i = myClass; var x = myClass; // And here is important that x is of type int! The MyClass looks roughly like this public class MyClass { public int Value{get;set;} public int AnotherValue{get;set;} public T GetSomething<T>() {..} } Every assignment of MyClass should return the Variable Value as Type int. So far i found implicit operator

问题 How to change the variable name numbering in ascending order to assign values to them. eg: car_1, car_2, car_3, car_4........ so on.. my coding is something like; for (i=1; i<20;i++){ $var[i] = $_POST["car_"i]; } foreach ......so on........ echo $var[12]."<br/>"; I need a way to increase the number of 'car_' to assign each car value to the '$var' array. I have tried to add it like this: $var[i] = $_POST["car_"&i]; AND $var[i] = $_POST["car_"i""]; and none of these work. I would very much

问题 I am developing a naive programming language, effectively a C code generator, and for simplification, I want to represent all functions as with no return type in C, with the return type being passed as the first parameter, if any. My question is whether this could present a compatibility or performance issue, I am not really sure what exactly is the difference, but common logic suggests that there is not much of a difference from the function assigning the returned value to the return address

问题 In Python, you use [:] when reassigning a variable to an original value (defined prior to the loop) at the start of each iteration. That is to say: original_1D = ['o', 'o', 'o'] for i in range(0,3): new = original_1D[:] # revert back to 'original_1D' list defined before loop new[i] = 'X' print new produces output that is both desired and expected: ['X', 'o', 'o'] ['o', 'X', 'o'] ['o', 'o', 'X'] My issue arises if the original list is multi-dimensional ( original_2D ). For example: original_2D

问题 I'm studying APL from here. Why am I getting this syntax error? 'computer' [ 1 2 3 ] ← 'COM' SYNTAX ERROR 'computer'[1 2 3]←'COM' ^ But if I save 'computer' in a variable I don't get the error: T ← 'computer' T computer T[1 2 3] ← 'COM' T COMputer What am I doing wrong? 回答1: 'computer' is a constant, and you can't change the value of a constant itself, only the current value of a variable. Think about it: If you could assign to 'computer' , then next time you wrote 'computer' , would you

问题 This question already has answers here : Why isn't tilde (~) expanding inside double quotes? [duplicate] (1 answer) Tilde expansion in quotes (3 answers) Tilde in path doesn't expand to home directory (4 answers) Closed last year . I have made a directory ~/test_myDir I then run the following bash script: x="myDir" dirName="~/test_$x" cd $dirName echo "hey" > test.txt I get the following error: test.sh: line 5: cd: ~/test_myDir: No such file or directory I then remove the quotes from the

问题 This question already has answers here : Why isn't tilde (~) expanding inside double quotes? [duplicate] (1 answer) Tilde expansion in quotes (3 answers) Tilde in path doesn't expand to home directory (4 answers) Closed last year . I have made a directory ~/test_myDir I then run the following bash script: x="myDir" dirName="~/test_$x" cd $dirName echo "hey" > test.txt I get the following error: test.sh: line 5: cd: ~/test_myDir: No such file or directory I then remove the quotes from the