Expressions can be stored as objects in the Policy Store, where they can be referenced by name from anywhere, including from other expressions. Any expression can pass values to a named expression through the placeholders %1 through %9 and the special placeholder %0. This is called pasting.
There are two types of named expressions: virtual user attributes and user classes. Virtual user attribute names start with a pound sign, and user class names start with an at sign. Both types of named expressions are followed by up to nine parameters. The syntax is similar to the syntax of a function:
#virtual_user_attribute(P1, P2, P3, P4, P5, P6, P7, P8, P9)
@user_class(P1, P2, P3, P4, P5, P6, P7, P8, P9)
When creating a named expression in the Policy Store, you can use built-in operators and functions, the literal data types, the placeholders, and other named expressions. Use the placeholders to pass variable data to the named expression. In the following example, the URL is updated during each iteration and thus, must be represented by the placeholder %1.
Example:
You can create a virtual attribute named #URLFile that accepts a URL and returns a filename:
#URLFile := { FIND(%1, '/')=0 ? %1 : #URLFile(AFTER(%1, '/')) }
Return_value=#URLFile('C:\My Documents\expression_syntax.doc')
Return_value='expression_syntax.doc'
In this example, the URL is passed to the built-in function FIND through the placeholder %1. FIND finds the first instance of "/" in the URL and returns its position. If "/" is not found, FIND returns 0 and #URLFile returns the filename. Otherwise, the URL is passed to the built-in function AFTER through the placeholder %1. AFTER returns that part of the URL that follows "/". The shortened URL is then passed to #URLFile. Recursion is supported.
The following table shows the values of the position and the URL at the completion of each iteration in this example:
|
Iteration |
Position |
URL |
|---|---|---|
|
1 |
3 |
'My Documents\expression_syntax.doc' |
|
2 |
16 |
'expression_syntax.doc' |
When certain built-in functions, such as ENUMERATE or LOOP, call a named expression multiple times, once for each element in a set, the named expression must be created using the special placeholder %0. For example, you can create an expression named #RTrimset that removes trailing spaces from any number of set elements:
#RTrimset := RTrim(%0)
Then, you can pass a set to #RTrimset through the built-in function ENUMERATE:
Return_value=ENUMERATE('First_name ^Middle_name ^Last_name ',#RTrimset)
Return_value='First_name^Middle_name^Last_name'
In this example, the set consists of three elements: the first, middle, and last names. ENUMERATE passes each name to #RTrimset. #RTrimset removes the trailing spaces and returns the shortened name to ENUMERATE. ENUMERATE includes each returned name in the resulting string and uses the caret character to separate them.
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