`timer'
-------

timer(INTERVAL,EXPR,VAL)
     :: Compute an expression under the interval timer.

RETURN
     result

INTERVAL
     interval (second)

EXPR
     expression to be computed

VAL
     a value to be returned when the timer is expired

   * `timer()' computes an expression under the interval timer.  If the
     computation finishes within the specified interval, it returns the
     result of the computation. Otherwise it returns the third argument.

   * The third argument should be distinguishable from the result on
     success.


     [0] load("cyclic");
     1
     [10] timer(10,dp_gr_main(cyclic(7),[c0,c1,c2,c3,c4,c5,c6],1,1,0),0);
     interval timer expired (VTALRM)
     0
     [11]

