The problem is that you cannot use ‘printf’ with va_args. You must use vprintf if you are using variable argument lists. vprint, vsprintf, vfprintf, etc. (there are also ‘safe’ versions in Microsoft’s C runtime that will prevent buffer overruns, etc.) You sample works as follows: void myprintf(char* fmt, …) { va_list args; va_start(args, fmt); vprintf(fmt, … Read more
You can’t. You have to manage for the caller to indicate the number of arguments somehow. You can: Pass the number of arguments as the first variable Require the last variable argument to be null, zero or whatever Have the first argument describe what is expected (eg. the printf format string dictates what arguments should … Read more
It’s a variadic macro. It means you can call it with any number of arguments. The three … is similar to the same construct used in a variadic function in C That means you can use the macro like this DEBUG(“foo”, “bar”, “baz”); Or with any number of arguments. The __VA_ARGS__ refers back again to … Read more
You can just accept the arguments by the variadic template and let typechecking check the validity later on when they are converted. You can check convertibility on the function interface level though, to make use of overload resolution for rejecting outright wrong arguments for example, by using SFINAE template<typename R, typename…> struct fst { typedef … Read more
def foo(msf: String, o: AnyRef, os: AnyRef*) = println( String.format(msf, (o :: os.toList).toArray : _* ))
Try this: Map(entities.map{e => e.id -> e}:_*) Explicitly typing it as a varargs using :_* seems to work.
Java cannot autobox an array, only individual values. I would suggest changing your method signature to public void doSomething(Integer… args) Then the autoboxing will take place when calling doSomething, rather than trying (and failing) when calling Arrays.asList. What is happening is Java is now autoboxing each individual value as it is passed to your function. … Read more
Ah found it…functions that accept variable length arguments are called Variadic Functions. Example: package main import “fmt” func MyPrint(format string, args …interface{}) { fmt.Printf(“[MY PREFIX] ” + format, args…) } func main() { MyPrint(“yay %d %d\n”,123,234); MyPrint(“yay %d\n “,123); MyPrint(“yay %d\n”); }
These type of functions are called variadic functions (Wikipedia link). They use ellipses (i.e., three dots) to indicate that there is a variable number of arguments that the function can process. One place you’ve probably used such functions (perhaps without realising) is with the various printf functions, for example (from the ISO standard): int printf(const … Read more
va_end is used to do cleanup. You don’t want to smash the stack, do you? From man va_start: va_end() Each invocation of va_start() must be matched by a corresponding invocation of va_end() in the same function. After the call va_end(ap) the variable ap is undefined. Multiple traversals of the list, each bracketed by va_start() and … Read more