In terms of readability, enumerations make better constants than macros, because related values are grouped together. In addition, enum defines a new type, so the readers of your program would have easier time figuring out what can be passed to the corresponding parameter. Compare #define UNKNOWN 0 #define SUNDAY 1 #define MONDAY 2 #define TUESDAY … Read more
I’ve done a screenshot to show where it is in Xcode, because it’s easier 🙂 Select project file Select the target you want Go to Build Settings Search for ‘preprocessor’ Add your preprocessor macro either for Debug, Release, or both.
You can use various recursive macro techniques to do things with variadic macros. For example, you can define a NUM_ARGS macro that counts the number of arguments to a variadic macro: #define _NUM_ARGS(X100, X99, X98, X97, X96, X95, X94, X93, X92, X91, X90, X89, X88, X87, X86, X85, X84, X83, X82, X81, X80, X79, X78, … Read more
SQR(1+1) expands to 1+1*1+1 which is 3, not 4, correct? A correct definition of the macro would be #define SQR(x) ((x)*(x)) which expands to (1+1)*(1+1) and, more important, shows you one of the reasons you shouldn’t use macros where they aren’t needed. The following is better: inline int SQR(int x) { return x*x; } Furthermore: … Read more
Using C++11, the non-macro form is: char arrname[5]; size_t count = std::extent< decltype( arrname ) >::value; And extent can be found in the type_traits header. Or if you want it to look a bit nicer, wrap it in this: template < typename T, size_t N > size_t countof( T ( & arr )[ N ] … Read more
Make the comma optional As DK. points out, the trailing comma can be made optional. Rust 1.32 You can use the ? macro repeater to write this and disallow multiple trailing commas: ($Name:ident { $($Variant:ident),* $(,)? }) => { // ^^^^^ Previous versions This allows multiple trailing commas: ($Name:ident { $($Variant:ident),* $(,)* }) => { … Read more
Call make command this way: make CFLAGS=-Dvar=42 And be sure to use $(CFLAGS) in your compile command in the Makefile. As @jørgensen mentioned , putting the variable assignment after the make command will override the CFLAGS value already defined the Makefile. Alternatively you could set -Dvar=42 in another variable than CFLAGS and then reuse this … Read more
No. Macros operate on the Abstract Syntax Tree, so they reason at the syntactic level: they reason about tokens and their spelling. For example: fn main() { let v = 3; } In this case, the AST will look something like: fn main \_ let-binding v \_ literal 3 If you ask a macro whether … Read more
While the ordinary macro system does not enable you to repeat the macro expansion many times, there is no problem with using a for loop in the macro: macro_rules! many_greetings { ($times:expr) => {{ for _ in 0..$times { println!(“Hello”); } }}; } If you really need to repeat the macro, you have to look … Read more
No, C# does not support preprocessor macros like C. Visual Studio on the other hand has snippets. Visual Studio’s snippets are a feature of the IDE and are expanded in the editor rather than replaced in the code on compilation by a preprocessor.