LET[let] @name = @name EXPANDED (1:2){ LEFT @number
| RIGHT @number }
The EXPAND command increases (expands) the size of a schedule by increasing
the size of each one of its intervals. In particular, some number of seconds
is subtracted from the left endpoint of each interval, while some other
number of seconds is added to the right endpoint of each interval.
Should the expansion of one interval cause it to overlap with another interval, the two intervals are merged into a single interval.
A graphical description of the EXPAND command is shown below.
Left increment - Right increment -- Input schedule -- --- --------- --------- Output schedule --------- ------------ ------------
The EXPAND command is normally used to extend intervals of opportunity in
order to provide a margin for error. In the following example, the intervals
in a schedule are expanded to allow for differences caused by shifting the
observer from Earth to HST.
FIND SEP SEPARATION OF IO
BY JUPITER
FROM EARTH
LESS THAN 0.5 DEGREES
WITHIN CONSTRAINTS
STEP SIZE 30 MINUTES;
LET SEP = SEP EXPANDED LEFT 5 seconds
RIGHT 5 seconds;
Compare with CONTRACT, which decreases the lengths of intervals (instead of
increasing them).