(追記) (追記ここまで)
Interval Notation
A notation for representing an interval as
a pair of numbers. The numbers are the endpoints of the interval.
Parentheses and/or brackets are used to show whether the endpoints are excluded or included.
For
example, [3, 8) is the interval of
real numbers between 3 and 8, including 3 and excluding 8.
Note: Many authors use reversed brackets instead of parentheses. For example, ]5,7[ refers to the interval from 5 to 7, exclusive. The interval in the example below would be written [–1, 2[.