BinarySearch := proc( A, value, low, high )
        description "recursive binary search";
        if high < low then
                FAIL
        else
                local mid := iquo( high + low, 2 );
                if A[ mid ] > value then
                        thisproc( A, value, low, mid - 1 )
                elif A[ mid ] < value then
                        thisproc( A, value, mid + 1, high )
                else
                        mid
                end if
        end if
end proc: