C++ 宏 if
WebIn computer programming, we use the if...else statement to run one block of code under certain conditions and another block of code under different conditions. For example, assigning grades (A, B, C) based on marks … WebExample explained. In the example above, time (22) is greater than 10, so the first condition is false.The next condition, in the else if statement, is also false, so we move on to the else condition since condition1 and condition2 is both false - and print to the screen "Good evening". However, if the time was 14, our program would print "Good day."
C++ 宏 if
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Web简单的 C++ 结构体字段 反射 利用模板元编程(和极少的宏),实现 非侵入式、声明式、零开销 结构体 静态反射. C++ 模板元编程 (template metaprogramming) 虽然功能强大,但也有 局限性 :. 不能通过 模板展开 … WebC++ if...else. The if statement can have an optional else clause. Its syntax is: if (condition) { // block of code if condition is true } else { // block of code if condition is false } The if..else statement evaluates the condition inside …
WebMay 24, 2024 · 用#if实现3个分支以上宏定义判断 在实际开发过程中经常会用到宏定义的判断,尤其是在硬件平台和软件平台较多的情况下,宏定义可以很好地在不同平台下条件编 … Web它的意思是,如果当前的宏未被定义,则对“程序段1”进行编译,否则对“程序段2”进行编译,这与 #ifdef 的功能正好相反。 三者之间的区别 最后需要注意的是,#if 后面跟的是“整型常量表达式”,而 #ifdef 和 #ifndef 后面跟的只能是一个宏名,不能是其他的。
WebJul 14, 2024 · 执行代码 1. #else. 执行代码 2. #endif. 假如编译时,确实满足条件(结果非0时),则生成的程序文件 (.exe文件)中不会有执行代码2的。. 如果用普通if语句,生成的程序文件就会有执行代码2,这个区别看看生成文件大小就可以知道。. 如果你的条件在程序编译前 … WebFeb 18, 2024 · 如果条件为假,assert宏会触发一个错误,并输出错误信息和行号。 例如: ```c #include int main() { int a = 0; assert(a != 0); return 0; } ``` 在上面的例子中,我们使用assert宏来检查变量a是否为0。由于a等于0,assert宏会触发一个错误,并输出错误信息和行号。
WebAug 16, 2024 · 先来说一下宏的几个作用 宏的几种用法#if与if的区别:1、属性作用不同#if是条件编译,条件编译是根据 宏条件 选择性地编译语句;而if是条件语句,条件语句是根 …
Web如上宏定义调用时会直接展开,我们可能会认为当前宏会对自己无限递归。但c语言为了防止无限递归造成死循环。语法规定,当宏在遇到自己时,就停止展开当前宏,也就是说,add(1)的结果为:“add(1)+1” 3、在我使用中经常用到的宏:条件编译 shannan watts documentary netflixWebIf statements in C++. The ability to control the flow of your program, letting it make decisions on what code to execute, is valuable to the programmer. The if statement allows you to control if a program enters a section of code or not based on whether a given condition is true or false. One of the important functions of the if statement is ... shannan watts autopsy picsWebAug 16, 2024 · 宏的几种用法. #if与if的区别:. 1、属性作用不同. #if是 条件编译 ,条件编译是根据 宏条件 选择性地编译语句;而if是条件语句,条件语句是根据条件 表达式 选择性地执行语句。. 2、执行时期不同(重点). shannan mitchemWebNov 22, 2024 · Decision Making in C/C++ helps to write decision driven statements and execute a particular set of code based on certain conditions.. The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t.But what if we want to do something else if the condition is false. Here comes the … polyphemus moth caterpillar host plantWeb宏定义技巧十五:使用宏定义进行元编程. 在c++中,我们可以使用宏定义来进行元编程,从而方便地生成一些元数据或代码。例如下面的代码定义了一个宏来生成一个元数据: shannan watts and kidsWebDec 4, 2012 · 4 Answers. Sorted by: 17. Besides #ifdef, the preprocessor supports the more general #if instruction; actually, #ifdef MACRO is a shortcut for #if defined (MACRO), … shannan twainshannan watts family today