switch-statement

问题 In C/C++, switch/case compares only an integral type with a compile time constants. It's not possible to use them to compare user/library defined types like std::string with runtime values. Why the switch statement cannot be applied on strings? Can we implement look-a-like switch/case which gives similar syntactic sugar and serves the purpose of avoiding plain if/else comparisons. struct X { std::string s; bool operator== (const X& other) const { return s == other.s; } bool operator== (const

问题 How does a switch statement immediately drop to the correct location in memory? With nested if-statements, it has to perform comparisons with each one, but with a switch statement it goes directly to the correct case. How is this implemented? 回答1: There are many different ways to compile a switch statement into machine code. Here are a few: The compiler can produce a series of tests, which is not so inefficient as only about log 2 (N) tests are enough to dispatch a value among N possible

问题 I want to use the following expression -(void)SwitchCondn{ int expression; int match1=0; int match2=1; switch (expression) { case match1: //statements break; case match2: //statements break; default: // statements break; } But I got When I research I found In order to work in Objective-C, you should define your constant either like this: #define TXT_NAME 1 Or even better, like this: enum {TXT_NAME = 1}; I have been using this methods since long time . Now my variable value will change in run

问题 I want to use the following expression -(void)SwitchCondn{ int expression; int match1=0; int match2=1; switch (expression) { case match1: //statements break; case match2: //statements break; default: // statements break; } But I got When I research I found In order to work in Objective-C, you should define your constant either like this: #define TXT_NAME 1 Or even better, like this: enum {TXT_NAME = 1}; I have been using this methods since long time . Now my variable value will change in run

问题 I want to use the following expression -(void)SwitchCondn{ int expression; int match1=0; int match2=1; switch (expression) { case match1: //statements break; case match2: //statements break; default: // statements break; } But I got When I research I found In order to work in Objective-C, you should define your constant either like this: #define TXT_NAME 1 Or even better, like this: enum {TXT_NAME = 1}; I have been using this methods since long time . Now my variable value will change in run

问题 I'm trying to implement something like if np.max(subgrid) == np.min(subgrid): middle_middle = cur_subgrid + 1 else: middle_middle = cur_subgrid Since the condition can only be determined at run-time, I'm using Keras syntax as following middle_middle = K.switch(K.max(subgrid) == K.min(subgrid), lambda: tf.add(cur_subgrid,1), lambda: cur_subgrid) But I'm getting this error: <ipython-input-112-0504ce070e71> in col_loop(j, gray_map, mask_A) 56 57 ---> 58 middle_middle = K.switch(K.max(subgrid) ==

问题 I'm trying to implement something like if np.max(subgrid) == np.min(subgrid): middle_middle = cur_subgrid + 1 else: middle_middle = cur_subgrid Since the condition can only be determined at run-time, I'm using Keras syntax as following middle_middle = K.switch(K.max(subgrid) == K.min(subgrid), lambda: tf.add(cur_subgrid,1), lambda: cur_subgrid) But I'm getting this error: <ipython-input-112-0504ce070e71> in col_loop(j, gray_map, mask_A) 56 57 ---> 58 middle_middle = K.switch(K.max(subgrid) ==

问题 Before you start criticizing and pointing me §8.7.2 of C# specification, read carefully :) We all know how switch looks like in C#. Ok so consider the class MainWindow with "nasty" Bar method static int barCounter = 0; public static int Bar() { return ++barCounter; } Somewhere in this class we have code like this Action switchCode = () => { switch (Bar()) { case 1: Console.WriteLine("First"); break; case 2: Console.WriteLine("Second"); break; } }; switchCode(); switchCode(); In the console

问题 Before you start criticizing and pointing me §8.7.2 of C# specification, read carefully :) We all know how switch looks like in C#. Ok so consider the class MainWindow with "nasty" Bar method static int barCounter = 0; public static int Bar() { return ++barCounter; } Somewhere in this class we have code like this Action switchCode = () => { switch (Bar()) { case 1: Console.WriteLine("First"); break; case 2: Console.WriteLine("Second"); break; } }; switchCode(); switchCode(); In the console

问题 Before you start criticizing and pointing me §8.7.2 of C# specification, read carefully :) We all know how switch looks like in C#. Ok so consider the class MainWindow with "nasty" Bar method static int barCounter = 0; public static int Bar() { return ++barCounter; } Somewhere in this class we have code like this Action switchCode = () => { switch (Bar()) { case 1: Console.WriteLine("First"); break; case 2: Console.WriteLine("Second"); break; } }; switchCode(); switchCode(); In the console