**English**

From a set of ints you have to create a list of closed intervals as tuples, so the intervals are covering all the values found in the set. After that you have to create an iterator object which is linked to this list.

A closed interval includes its endpoints! The interval *1..5*, for example,
includes each value *x* that satifies the condition
*1 <= x <= 5*.

Values can only be in the same interval if the difference between a value and the next
smaller value in the set equals one, otherwise a new interval begins. Of course, the
start value of an interval is excluded from this rule.

A single value, that does not fit into an existing interval becomes the start- and
endpoint of a new interval.

**Input:** A set of ints.

**Output:** An iterator object linked to the list of tuples.

**Examples:**

create_intervals({1, 2, 3, 4, 5, 7, 8, 12}) == [(1, 5), (7, 8), (12, 12)] create_intervals({1, 2, 3, 6, 7, 8, 4, 5}) == [(1, 8)]