variadic-functions

How can I (if at all) emulate variadic functions (not methods) so that I could write sum 1 2 3 sum 1 2 3 4 5 sum 1 2 3 4 5 6 7 // etc. The code above is just meant as an example - obviously if I would have to sum up a list then [ 1; 2 ; 3] |> List.sum is a much better way. However I am looking for a structurally similar solution like this Haskell solution What is also important is that the normal syntax for function calls and parameter values remains the same. So sum 1 2 3 vs sum(1, 2, 3) which effectively means that let sum ([<ParamArray>] arr) = ... is not wanted in this specific case. The

Please help! I need this conversion to write wrapper for some C headers for Delphi. As an example: function pushfstring(fmt: PAnsiChar): PAnsiChar; cdecl; varargs; external; ... function PushString(fmt: AnsiString; const args: array of const): AnsiString; begin Result := AnsiString(pushfstring(PAnsiString(fmt), args)); // it's incorrect :/ end; How can I convert "array of const" to "varargs"? edit : function PushString is actually inside the record (I gave a simplified example), and I do not have direct access to pushfstring. Direct call is excluded. edit 2 :I write the units for LUA library

I have a function that tries to log stuff to the console and also to a log file, but it doesn't work. The second use of the variable length argument gives garbage written to the console. Any ideas? void logPrintf(const char *fmt, ...) { va_list ap; // log to logfile va_start(ap, fmt); logOpen; vfprintf(flog, fmt, ap); logClose; va_end(ap); va_list ap2; // log to console va_start(ap2, fmt); printf(fmt, ap2); va_end(ap2); } The original code fails because it tries to use printf() where it needs to use vprintf() . Taking dubious points like the logOpen and logClose statements at face value (given

PHP supports the spread syntax for variadic functions . In JavaScript, you can use the spread syntax to do this : var a = [1, 2]; var b = [...a, 3, 4]; console.log(b); // [1, 2, 3, 4] However, trying to do this in PHP: $a = [1, 2]; $b = [...$a, 3, 4]; var_dump($b);die; Results in this error: Parse error: syntax error, unexpected '...' (T_ELLIPSIS), expecting ']' Is using the spread syntax this way not allowed in PHP? If so, is there an equally-as-elegant way to achieve the same effect? Erald Karakashi The spread operator in the arrays RFC has been implemented in PHP 7.4: $ary = [3, 4, 5];

I was experimenting with variable constructor arguments for case classes in Scala, but am unable to pass them to the constructor of a case classes' parent: abstract case class Node(val blocks: (Node => Option[Node])*) case class Root(val elementBlocks: (Node => Option[Node])*) extends Node(elementBlocks) the above doesn't compile... is it actually possible to do this? This works with 2.7: abstract case class A(val a: String*) case class B(val b: String*) extends A(b:_*) Should work with 2.8. You need to use the :_* syntax which means "treat this sequence as a sequence" ! Otherwise, your

For example ((fn-stringappend string-append) "a" "b" "c") I know how to handle this (f x y z) . But what if there's an unknown number of parameters? Is there any way to handle this kind of problem? In Scheme you can use the dot notation for declaring a procedure that receives a variable number of arguments (also known as varargs or variadic function ): (define (procedure . args) ...) Inside procedure , args will be a list with the zero or more arguments passed; call it like this: (procedure "a" "b" "c") As pointed out by @Arafinwe, here's the equivalent notation for an anonymous procedure:

Basically after doing a query I'd like to take the resulting rows and produce a []map[string]interface{} , but I do not see how to do this with the API since the Rows.Scan() function needs a specific number of parameters matching the requested number of columns (and possibly the types as well) to correctly obtain the data. Again, I'd like to generalize this call and take any query and turn it into a []map[string]interface{} , where the map contains column names mapped to the values for that row. This is likely very inefficient, and I plan on changing the structure later so that interface{} is

Given the following companion object with overloaded versions of apply : object List { def apply[T](): List[T] = new Nil def apply[T](x1: T): List[T] = new Cons(x1, new Nil) def apply[T](x1: T, x2: T): List[T] = new Cons(x1, new Cons(x2, new Nil)) def apply[T](elems: T*): List[T] = elems.foldRight(List[T])((elem, l) => new Cons(elem, l)) } And the two instantiations List(1) // Error - Ambiguity List('a', 'b') // Works fine scalac complains about the first instantiation ( ambiguous reference to overloaded definition ) because both the single argument and the varargs method are equally specific