Go
I challenge anybody to see the bug, who doesn't already know where it is. I added a few (truthful) comments to explain the code to non-Goers.
Try to find it yourself, if you're so inclined, before reading the comment section below (where somebody will surely spoil it.)
Here is a link to the playground: http://play.golang.org/p/UwunxiXKP7
package main
import "fmt"
// Aim: to define an integer type that by default is printed in hex notation (0xab..)
type hexInt int
// Implementation of the Stringer interface, used by Println for conversion to string.
func (h hexInt) String() string {
// "%#x" is the alternate form of "%x", which uses lowercase a-f and adds 0x in front.
return fmt.Sprintf("%#x", h)
}
func main() {
// Create a variable of type hexInt with the value 42 and print it.
var h hexInt = 42
fmt.Println(h)
}