PSLang Expressions

An expression is some sequence of operations that yields a result. A literal value, a variable, or a function by themselves can be an expression. The following are valid expressions:

5
"3"
myfunction( 1 )
5+3
5 + "3"
"5" + "3"
"5" + myfunction( innerfunction() - 6 )
$x + $y + $z

A PSLang expression can include a sequence of variable declarations (including initializers) and function calls. The final statement must be an expression; its value is taken as the overall result.

Here is a sequence of statements:

var $a = "hello";
var $b = ", world";
var $c = strlen( $a );
$a + $b + " - length: " + $c

This is acceptable as a PSLang expression because the last statement is itself a normal expression. The result here would be: hello, world - length: 5.

In the Bravura Security Fabric GUI, the same sequence of statements would be written on one line:

var $a = "hello"; var $b = ", world"; var $c = strlen( $a); $a + $b + " - length:" + $c

PSLang supports the following types of expressions:

A boolean expression yields an integer result, where zero is interpreted as false , and any value other than zero is interpreted as true .

Bitwise operators (~, &, —) must not be confused with logical operators ( ! , &&, ——). Although PSLang does not support “^”, the bitwise exclusive or operator (xor), you can achieve the same results using: (A & ~B ) | ( ~A & B ).

The PSLang + operator can be used with numerical values, or to append string values. In an expression such as x+y, where x is a string and y is a number, y is converted to a string and appended to x.

The ternary operator works the same way as the C++ ternary operator ( ?: ). The test expression is evaluated, and if the result is non-zero, the true _ part expression is evaluated and returned. Otherwise, the false _ part expression is evaluated and returned.

The order of evaluation proceeds according to the precedence of the operators in the expression. The following table lists the precedence of the operators, with the highest priority at the top of the list.

Evaluation of the expression moves left to right and stops at the earliest possible pass/fail decision; unnecessary conditions are not evaluated.

The user interface can be configured to offer auto-completion of variable or function calls when writing PSLang expressions. Enabling auto-complete provides quick access to help and formatting information.

Only the PSLang functions in the string, time, and misc sections are available for auto-completion.

The auto-complete drop-down list appears as you type a valid expression into a PSLang text area. Only variables, functions and completion options that match your typing are displayed. For detailed information, click the ? link to the right of each listed item.

To see the complete drop-down list of all available options:

Navigation through the list can be done with the mouse, or using the ↑ and ↓ keys. Selections can be made using the Enter or Tab keys. The Esc key closes the menu.

The PSLang auto-completion functionality can be disabled or enabled by clicking disable auto-completion or enable auto-completion beneath any PSLang text area.

The default settings for the PSLang auto-complete functionality are controlled by the config.js script, located in the \<instance>\design\src\js\ directory. In this script, the AutoCompletePslang group has the following options:

This section illustrates the use of PSLang expressions by explaining expressions used by default by Bravura Security Fabric .

Each of these expressions use an iif() function, which takes 3 parameters – iif(boolean expression, "true-part", "false-part" )

It evaluates the boolean expression, and when it’s true, it returns the true-part. Otherwise, it returns the false-part.

In PSLang, a variable is prefixed by $. The variables discussed in this chapter represent a string of characters, or an array of strings.

The characters [n] are placed after variable names to index the n th character in a string, or the n th value in an array, starting from 0. This is used with profile attributes, which can have multiple values. The first of an array of values is represented by $ATTRIBUTE[0], the second by $ATTRIBUTE[1], and so on.

All built-in attributes must be expressed as an array. That is – $FIRST_NAME[0] , $OTHER_NAME[0], $LAST_NAME[0].

iif( (size($LAST_NAME) > 0 && size($FIRST_NAME) > 0),
substr($LAST_NAME[0], 0, 5) + substr($FIRST_NAME[0], 0, 1),
""
)

iif( size($OTHER_NAME) > 0,
$FIRST_NAME[0] + " " + $OTHER_NAME[0] + " " + $LAST_NAME[0],
$FIRST_NAME[0] + " " + $LAST_NAME[0]
)

var $other = iif( size($OTHER_NAME) > 0, $OTHER_NAME[0], "" );
$other[0];