Intervals
An interval is a set of numbers between upper and lower bound. To create an interval, type e.g. 2 < x < 3
in
Input Bar. Interval in previous example is open. You can also define closed (2 ≤ x ≤ 3
) and
semiclosed (2 ≤ x < 3
) intervals.
See also Boolean values. 
To determine whether number c belongs to interval r type r(c)
into the Input Bar, the result will be a Boolean
value. Generalization of intervals are Inequalities.
Commands for intervals

Min, Max, Midpoint for an interval with lower bound a and upper bound b return numbers a, b and \(\frac{a+b}2\) respectively. The result doesn’t depend on whether the interval is open, closed or semiclosed.

Point returns a moveable point whose xcoordinate belongs to the interval and ycoordinate is 0.

PointIn returns a moveable point whose xcoordinate belongs to the interval and ycoordinate may be changed arbitrarily.