`loop', `break', `return', `continue'
-------------------------------------

There are three kinds of statements for loops (repetitions): the
`while' statement, the `for' statement, and  the `do' statement.

   * `while' statement
     It has the following form.

          while ( expression ) statement

     This statement specifies that `statement' is repeatedly evaluated
     as far as the `expression' evaluates to a non-zero value.  If the
     expression 1 is given to the `expression', it forms an infinite
     loop.

   * `for' statement
     It has the following form.

          for ( expr list-1; expr; expr list-2 ) statement

     This is equivalent to the program

          expr list-1 (transformed into a sequence of simple statement)
          while ( expr ) {
              statement
              expr list-2 (transformed into a sequence of simple statement)
          }

   * `do' statement
          do {
              statement
          } while ( expression )

     This statement differs from `while' statement by the location of
     the termination condition: This statement first execute the
     `statement' and then check the condition, whereas `while'
     statement does it in the reverse order.

As means for exiting from loops, there are `break' statement and
`return' statement.  The `continue' statement allows to move the
control to a certain point of the loop.
   * `break'
     The `break' statement is used to exit the inner most loop.

   * `return'
     The `return' statement is usually used to exit from a function call
     and it is also effective in a loop.

   * `continue'
     The `continue' statement is used to move the control to the end
     point of the loop body.  For example, the last expression list
     will be evaluated in a `for' statement, and the termination
     condition will be evaluated in a `while' statement.

