Xcode 11 • Swift 5.1 or later extension BinaryInteger { var degreesToRadians: CGFloat { CGFloat(self) * .pi / 180 } } extension FloatingPoint { var degreesToRadians: Self { self * .pi / 180 } var radiansToDegrees: Self { self * 180 / .pi } } Playground 45.degreesToRadians // 0.7853981633974483 Int(45).degreesToRadians // 0.7853981633974483 Int8(45).degreesToRadians // 0.7853981633974483 … Read more
Linux kernel uses a nice implementation of ARRAY_SIZE to deal with this issue: #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr)) with #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) and #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) Of course this is portable only in GNU C as it makes use of two instrinsics: typeof operator and __builtin_types_compatible_p function. Also it uses … Read more
It’s a preprocessor macro. All of it is preprocessor syntax, that basically says, if this macro has not already been defined, define it and include all code between the #ifndef and #endif What it accomplishes is preventing the inclusion of file more than once, which can lead to problems in your code. Your question: And … Read more
Try #include <string.h> #define __FILENAME__ (strrchr(__FILE__, “https://stackoverflow.com/”) ? strrchr(__FILE__, “https://stackoverflow.com/”) + 1 : __FILE__) For Windows use ‘\\’ instead of “https://stackoverflow.com/”.
Macros don’t directly expand recursively, but there are workarounds. When the preprocessor scans and expands pr(5): pr(5) ^ it creates a disabling context, so that when it sees pr again: ((5==1)? 1 : pr(5-1)) ^ it becomes painted blue, and can no longer expand, no matter what we try. But we can prevent our macro … Read more
The C FAQ has some examples of historical machines with non-0 NULL representations. From The C FAQ List, question 5.17: Q: Seriously, have any actual machines really used nonzero null pointers, or different representations for pointers to different types? A: The Prime 50 series used segment 07777, offset 0 for the null pointer, at least … Read more
If you can’t use parentheses and you don’t like Mike’s SINGLE_ARG solution, just define a COMMA: #define COMMA , FOO(std::map<int COMMA int>, map_var); This also helps if you want to stringify some of the macro arguments, as in #include <cstdio> #include <map> #include <typeinfo> #define STRV(…) #__VA_ARGS__ #define COMMA , #define FOO(type, bar) bar(STRV(type) \ … Read more
Andrey Tarasevich provides the following explanation: On Google Groups On bytes.com [Minor changes to formatting made. Parenthetical annotations added in square brackets []]. The whole idea of using ‘do/while’ version is to make a macro which will expand into a regular statement, not into a compound statement. This is done in order to make the … Read more
typedef obeys scoping rules just like variables, whereas define stays valid until the end of the compilation unit (or until a matching undef). Also, some things can be done with typedef that cannot be done with define. For example: typedef int* int_p1; int_p1 a, b, c; // a, b, c are all int pointers #define … Read more
You can follow it with a semicolon and make it look and act more like a function. It also works with if/else clauses properly then. Without the while(0), your code above would not work with if (doit) INIT_LIST_HEAD(x); else displayError(x); since the semicolon after the macro would “eat” the else clause, and the above wouldn’t … Read more