How to write binary literals in Scala?

Using the new "implicit class" and "value class" mechanisms in 2.10, you can write something like this to add convenience methods without the overhead of object creation:

implicit class IntToBase( val digits:String ) extends AnyVal {
  def base(b:Int) = Integer.parseInt( digits, b )
  def b = base(2)
  def o = base(8)
  def x = base(16)
}

That allows you to do things like

"555".o  // 365 decimal

and no IntToBase object is ever actually created.

In 2.10 you can create a string interpolator for that, e.g. it's possible to write b"0010" to mean 2. Using macros you can get rid of associated runtime overhead and do the conversion at compile-time. Take a look at Jason Zaugg's macrocosm to see it in action:

scala> b"101010"
res4: Int = 42

scala> b"102"
<console>:11: error: exception during macro expansion: invalid binary literal
              b"102"
              ^

If performance is not an issue, you can use a String and convert it to an integer.

val x = Integer.parseInt("01010101", 2)

Binary numbers aren't supported directly in part because you can easily convert from hexadecimal to binary and vice versa. To make your code clearer, you can put the binary number in a comment.

val x = 0x55 //01010101