網頁在把宏引入代码中，会多出一个分号，从而会报错。 使用do {….}while (0) 把它包裹起来，成为一个独立的语法单元，从而不会与上下文发生混淆。 同时因为绝大多数的编译器都能够识别do {…}while (0)这种无用的循环并进行优化，所以使用这种方法也不会导致程序的性能降低。 在MFC, 在MFC的afx.h文件里面， 你会发现很多宏定义都是用了do...while (0) …

網頁2015年12月28日 · 1. 增加代码的适应性 下面的宏定义没有使用do {...}while (0) #define FOO (x) foo (x); bar (x); 这样宏定义，单独调用不会出现问题，例如： FOO ( 100) 宏扩展后变成： 这样调用FOO没有任何问题，但是FOO（x）不能放入控制语句中，例如 经过宏扩展后，变成了 if (condition) foo (x);bar (x); else ...; 这样就导致了 语法错误 ，语法错误并不可怕， …

網頁This is a coding idiom that allows a multi-line macro to be used anywhere that a single statement can be used. Since the conditional expression of the do loop is a constant value, the compiler will not generate any additional code to process the loop, so this idiom does not add any overhead to the code when it is executed.

網頁define verb de· fine di-ˈfīn defined; defining 1 a : to determine the essential qualities of define the idea of loyalty define a circle b : to set forth the meaning of define a word c : to specify (as a programming task) for a computer to use define a procedure 2 a : to fix or mark the limits of the boundary was clearly defined b

網頁The syntax for creating a constant using #define in the C language is: #define CNAME value OR #define CNAME (expression) CNAME The name of the constant. Most C programmers define their constant names in uppercase, but it is not a requirement of the C Language. value The value of the constant. expression

網頁Arduino - Home

網頁2016年6月16日 · How do I define a variable without assigning it... Learn more about defining variablesIn some cases, equations that you might not think of normally as being optimizations can be rewritten: the expression A(x) == B(x) can potentially be rewritten in terms of minimizing ...

網頁2013年11月14日 · #define is often misunderstood because it isn’t a programming statement. Instead, it sets up a macro which causes a text replace to occur before code is compiled. For example in this code: #define pin 13 void setup() { pinMode(pin, OUTPUT); } void loop() { digitalWrite(pin, HIGH); delay(500); digitalWrite(pin, LOW); delay(500); }

網頁2018年11月21日 · Interferes with children's learning, development, and success at play, affecting not only the disruptive child but also the other children. Is harmful to and threatens the safety of the child, and the other children and even the adults. Interferes with teachers' ability to teach and all of the children's opportunities to learn.

網頁2014年7月31日 · If you want the user to be able to select things at runtime, you could use command-line arguments, environment variables, or configuration files, etc etc etc. But it all depends on what your actual goal is. You could make the value you want to change something that you read in from the keyboard but other than that I can't think of any way …