/*  Title:      Pure/library.scala

     Author:     Makarius

 Basic library.

 */

 package isabelle

 import java.lang.System

 object Library

 {

   /* reverse CharSequence */

   class Reverse(text: CharSequence, start: Int, end: Int) extends CharSequence

   {

     require(0 <= start && start <= end && end <= text.length)

     def this(text: CharSequence) = this(text, 0, text.length)

     def length: Int = end - start

     def charAt(i: Int): Char = text.charAt(end - i - 1)

     def subSequence(i: Int, j: Int): CharSequence =

       if (0 <= i && i <= j && j <= length) new Reverse(text, end - j, end - i)

       else throw new IndexOutOfBoundsException

     override def toString: String =

     {

       val buf = new StringBuilder(length)

       for (i <- 0 until length)

         buf.append(charAt(i))

       buf.toString

     }

   }

   /* timing */

   def timeit[A](e: => A) =

   {

     val start = System.currentTimeMillis()

     val result = Exn.capture(e)

     val stop = System.currentTimeMillis()

     System.err.println((stop - start) + "ms elapsed time")

     Exn.release(result)

   }

 }