Syntax:
variable-name = new result-type index-type-list

The index-type-list is a list of one or more type names expressed in either of two syntaxes (or a mix of both, if the mood suits you):

[ type-name, type-name, type-name ]
    or
[ type-name ][ type-name ][ type-name ]

Description:
The array creation statement creates a new empty array. The array has a result type, and one or more index types. Valid types are: String, Integer, Float, Date, DateTime, Time, DateDiff and Boolean. Note that any of these types may be used as an index type.  In many languages this would be called a map, dictionary or sparse array. The firstIndex() and lastIndex() functions, as well as the for/in loop, retrieve the values from the array based on the sorted order of the index values, not based on the order they were added.

Example:
For the following short program:

usHistory = new String[Date];
usHistory[toDate("12/15/1791")] = "Bill of Rights Ratified";
usHistory[toDate("07/04/1776")] = "Independence Day";
usHistory[toDate("06/21/1788")] = "U.S. Constitution is Ratified";
usHistory[toDate("10/19/1781")] = "U.S. Wins Revolutionary War";
outStr = "";
for (date in usHistory) {
    outStr += date + " - " + usHistory[date] + "\n";
}

Alternatively, the last three lines could be written with the more advanced looping syntax like so:

for (date, event in usHistory) {
    outStr += date + " - " + event + "\n";
}

With either looping syntax result in outStr would be:

07/04/1776 - Independence Day
10/19/1781 - U.S. Wins Revolutionary War
06/21/1788 - U.S. Constitution is Ratified
12/15/1791 - Bill of Rights Ratified