Idiom #225 Declare and use an optional argument

Declare an optional integer argument x to procedure f, printing out "Present" and its value if it is present, "Not present" otherwise

#include <optional>
#include <iostream>

void f(std::optional<int> x = {}) {
  if (x) {
    std::cout << "Present" << x.value();
  } else {
    std::cout << "Not present";
  }
}

#include <optional>
#include <iostream>

void f(std::optional<int> x = {}) {
  std::cout << (x ? "Present" + std::to_string(x.value()) : "Not Present");
}

static void f(int? x = null)
{
	Console.WriteLine(x.HasValue ? "Present" : "Not Present");
}

subroutine f(x)
  integer, optional :: x
  if (present(x)) then
    print *,"Present", x
  else
    print *,"Not present"
  end if
end subroutine f

func f(x ...int) {
	if len(x) > 0 {
		println("Present", x[0])
	} else {
		println("Not present")
	}
}

function f(x) {
	console.log(x ? `Present: ${x}` : 'Not present');
}

function f( x )
	if x then
		print("Present", x)
	else
		print("Not present")
	end
end

function f(?int $x = null) {
    echo $x ? 'Present' . $x : 'Not present';
}

procedure f; overload;
begin
  writeln('not present');
end;

procedure f(x: integer); overload;
begin
  writeln('present');
end;

def f(x=None):
    if x is None:
        print("Not present")
    else:
        print("Present", x)

def f( x=nil )
  puts x ? "present" : "not present"
end

fn f(x: Option<()>) {
    match x {
        Some(x) => println!("Present {}", x),
        None => println!("Not present"),
    }
}

tkoenig