Why Crystal Is My Next Language(fgimian.github.io)

    type Colours = (Red, White, Blue);

    type Colours int

    const (
        Red Colours = iota
        White
        Blue
    )

    function Sin(const num: Integer): Double; external 'ext name';

   // #include <stdio.h>
   // #include <errno.h>
   import "C"

   func Sin (num uint) float32 {
      return C.sin
   }

   procedure Swap(var a,b:Integer);
   var
      temp: Integer;
   begin
      temp:=a;
      a:=b;
      b:=temp
   end;

   Swap(x, y)
   Swap(nil, y) { compiler error: Got "Pointer" expected "SmallInt" }

   func Swap (a *int, b*int) {
      var temp = *a
      *a = *b
      *b = temp
   }

 
   Swap(&x, &y)
   Swap(nil, &y) { runtime error: Invalid memory address or nil pointer dereference }