Commit 31356e2b by Jean-Christophe Filliâtre

### new example: array_most_frequent

`(a simple programming exercise, with a simple proof)`
parent 9004bddb
 use int.Int use ref.Refint use array.Array use array.NumOfEq (** A simple programming exercise: find out the most frequent value in an array Using an external table (e.g. a hash table), we can easily do it in linear time and space. However, if the array is sorted, we can do it in linear time and constant space. *) let most_frequent (a: array int) : int requires { length a > 0 } requires { forall i j. 0 <= i <= j < length a -> a[i] <= a[j] } ensures { numof a result 0 (length a) > 0 } ensures { forall x. numof a x 0 (length a) <= numof a result 0 (length a) } = let ref r = a[0] in let ref c = 1 in let ref m = 1 in for i = 1 to length a - 1 do invariant { c = numof a a[i-1] 0 i } invariant { m = numof a r 0 i } invariant { forall x. numof a x 0 i <= m } if a[i] = a[i-1] then begin incr c; if c > m then begin m <- c; r <- a[i] end end else c <- 1 done; r