It is a degenerate syntax that is allowed but provides no benefit. Most modern compilers can be provoked into emitting a warning about it; by default, they may not. Without the typedef name, the keyword typedef is superfluous; in your example, it is completely equivalent to: enum test { one }; Another place where it … Read more
arr //arr arr [] //is an array (so index it) * arr [] //of pointers (so dereference them) (* arr [])() //to functions taking nothing (so call them with ()) void (* arr [])() //returning void so your answer is void (* arr [])() = {}; But naturally, this is a bad practice, just use … Read more
A common usage pattern of typedef in Dart is defining a callback interface. For example: typedef void LoggerOutputFunction(String msg); class Logger { LoggerOutputFunction out; Logger() { out = print; } void log(String msg) { out(msg); } } void timestampLoggerOutputFunction(String msg) { String timeStamp = new Date.now().toString(); print(‘${timeStamp}: $msg’); } void main() { Logger l = … Read more
It has a similar syntax, except you remove the identifier from the pointer: using FunctionPtr = void (*)(); Here is an Example If you want to “take away the uglyness”, try what Xeo suggested: #include <type_traits> using FunctionPtr = std::add_pointer<void()>::type; And here is another demo.
In C, declaring your enum the first way allows you to use it like so: TokenType my_type; If you use the second style, you’ll be forced to declare your variable like this: enum TokenType my_type; As mentioned by others, this doesn’t make a difference in C++. My guess is that either the person who wrote … Read more
In POSIX, names ending with _t are reserved, so if you are targeting a POSIX system (e.g., Linux), you should not end your types with _t.
The reason is that when instantiating a class template, all its declarations (not the definitions) of its member functions are instantiated too. The class template is instantiated precisely when the full definition of a specialization is required. That is the case when it is used as a base class for example, as in your case. … Read more
Most recent way (Swift 3; May 2017) to forward declare the enum (NS_ENUM/NS_OPTION) in objective-c is to use the following: // Forward declaration for XYZCharacterType in other header say XYZCharacter.h typedef NS_ENUM(NSUInteger, XYZCharacterType); // Enum declaration header: “XYZEnumType.h” #ifndef XYZCharacterType_h #define XYZCharacterType_h typedef NS_ENUM(NSUInteger, XYZEnumType) { XYZCharacterTypeNotSet, XYZCharacterTypeAgent, XYZCharacterTypeKiller, }; #endif /* XYZCharacterType_h */`
In general, it’s a bad practice. The significant problem is that it does not play well with const: typedef type_t *TYPE; extern void set_type(TYPE t); void foo(const TYPE mytype) { set_type(mytype); // Error expected, but in fact compiles } In order for the author of foo() to express what they really mean, the library that … Read more
In the first case, your struct has two equivalent names: struct Element (where Element is a struct tag) and Element (where Element is a typedef, an alias for an existing type). In the second case, you just didn’t define a tag for the struct. Normally that would be perfectly valid, but here you’re referring to … Read more