~ Consider the following sort routine:

procedure selectsort(var r: array [1 .. n] of integer);

var j, k, small: integer;

begin if n > 1 then for k:= 1 to n - 1 do small:= k;

for j:= k + 1 to n do if r[j] < r[small] then small:= j end end;

swap(r[k], r[small])

end end end selectsort;

Determine the function (by means of pre- and postconditions) of this routine using stepwise abstraction.