variable-assignment

问题 This question already has an answer here : destructuring falsey and null with default parameters (1 answer) Closed 2 years ago . I am learning javascript and I got kind of stuck with ES6 syntax while trying to give a default value to a variable when destructuring. Basically, I am trying to assign a variable giving the value of an object's property to it and if the value is false/null/undefined, I want it to be an empty object. For example, let foo = { prop1: 'hello!', prop2: null } const

问题 I came across a code snippet which included $a = & $b; but hadn't tested whether $b actually existed ( if (isset($b)) ). I wasn't sure how PHP handled this so I knocked up a quick bare test and now I'm even more intrigued. $a = array('a'=>'b', 'x'=>'y'); $b = array(); $b[10] = &$a['a']; $b[11] = &$a['ppp']; var_dump($a); var_dump($b); echo (isset($a['ppp']) ? "SET" :" NOT SET") . "\n"; echo (isset($b[11]) ? "SET" :" NOT SET") . "\n"; It's bare code but what the output shows is: Just the bare

问题 If you have a C function which returns an integer, you could write a statement like this: MyInt &= MyFunc(); ...where we're using the bitwise-AND assignment operator. The question is: is MyFunc() guaranteed to be executed, even if MyInt equals zero? Likwise, if we used the bitwise-OR assignment operator (|=), would MyFunc() always be executed, even if MyInt were set to all ones? Put another way: is lazy evaluation permitted in C for bitwise operators? 回答1: MyInt &= MyFunc(); is equivalent to:

问题 I have a Java array defined already e.g. float[] values = new float[3]; I would like to do something like this further on in the code: values = {0.1f, 0.2f, 0.3f}; But that gives me a compile error. Is there a nicer way to define multiple values at once, rather than doing this?: values[0] = 0.1f; values[1] = 0.2f; values[2] = 0.3f; Thanks! 回答1: Yes: float[] values = {0.1f, 0.2f, 0.3f}; This syntax is only permissible in an initializer. You cannot use it in an assignment, where the following

问题 I have a Java array defined already e.g. float[] values = new float[3]; I would like to do something like this further on in the code: values = {0.1f, 0.2f, 0.3f}; But that gives me a compile error. Is there a nicer way to define multiple values at once, rather than doing this?: values[0] = 0.1f; values[1] = 0.2f; values[2] = 0.3f; Thanks! 回答1: Yes: float[] values = {0.1f, 0.2f, 0.3f}; This syntax is only permissible in an initializer. You cannot use it in an assignment, where the following

问题 I have a Java array defined already e.g. float[] values = new float[3]; I would like to do something like this further on in the code: values = {0.1f, 0.2f, 0.3f}; But that gives me a compile error. Is there a nicer way to define multiple values at once, rather than doing this?: values[0] = 0.1f; values[1] = 0.2f; values[2] = 0.3f; Thanks! 回答1: Yes: float[] values = {0.1f, 0.2f, 0.3f}; This syntax is only permissible in an initializer. You cannot use it in an assignment, where the following

问题 Assuming a purely non-optimizing compiler, is there any difference in machine code between initializing a variable and assigning it a value after declaration? Initialization method : int x = 2; Assignment method : int x; x = 2; I used GCC to output the assembly generated for these two different methods and both resulted in a single machine instruction: movl $2, 12(%esp) This instruction just sets the memory held by the x variable to the value of 2 . GCC may be optimizing this because it can

问题 Assuming a purely non-optimizing compiler, is there any difference in machine code between initializing a variable and assigning it a value after declaration? Initialization method : int x = 2; Assignment method : int x; x = 2; I used GCC to output the assembly generated for these two different methods and both resulted in a single machine instruction: movl $2, 12(%esp) This instruction just sets the memory held by the x variable to the value of 2 . GCC may be optimizing this because it can

问题 I need to assign N entities (each with possible parents and possible children) to M computation nodes while satisfying the following optimization conditions: Children of an entity want to be assigned to the same computation node (to maximize data locality among siblings) The distribution of entities should be as even as possible (i.e. no overtaxing of a single node). I'm looking for some suggestions on heuristic methods to solve this problem. I've read http://en.wikipedia.org/wiki/Assignment

问题 I need to assign N entities (each with possible parents and possible children) to M computation nodes while satisfying the following optimization conditions: Children of an entity want to be assigned to the same computation node (to maximize data locality among siblings) The distribution of entities should be as even as possible (i.e. no overtaxing of a single node). I'm looking for some suggestions on heuristic methods to solve this problem. I've read http://en.wikipedia.org/wiki/Assignment