Evaluating expressions

LN Studio enables you to create watch expressions.

When the Virtual Machine suspends a session (due to hitting a breakpoint or stepping through code), you can evaluate these expressions in the context of a stack frame.

Creating watch expressions

To create a watch expression that is executed each time you step through the execution, complete one of these steps:

Right-click in the Expressions view. On the shortcut menu, select Add Watch Expression and type the name of the expression you want to evaluate.
In the LN Studio Script Editor, select the expression you want to evaluate. Right-click and, on the shortcut menu, select Watch.
When you are debugging a session, go to the Variables view. Right-click a variable you want to evaluate and, on the shortcut menu, click Create Watch Expression.
Specify a condition or modification watchpoint; a watch expression is added automatically.

The watch expressions you enter are stored automatically. So, the next time you debug a session, the same expressions are available in the Expressions view.

Executing Assignment Expressions

To define an expression that must be executed only once, right-click in the script editor or right-click in the Expressions view and, on the shortcut menu, select Execute Assignment Expression. The Execute Assignment Expression dialog starts. For details, see the dialog's online help.

Note: If you select a variable name in the script editor before you start the Execute Assignment Expression command, this expression is displayed in the dialog: <variable name>:=

For example, you select the task.child.process variable in the script. Then, on the shortcut menu, you click Execute Assignment Expression. The Execute Assignment Expression dialog starts and contains this expression: task.child.process:=

Evaluating expressions

To evaluate expressions:

Switch to the Debug perspective and open the Expressions view.
Start a session in debug mode.
In the Debug view, select the stack frame in which you want to perform an evaluation. The expressions in the Expressions view are evaluated automatically.
- For the detail pane of the Expressions view, the evaluation context is a selected variable.
- If you do not select a variable, the selected stack frame is the context.

Note: When you edit a watch expression in the Expressions view, you can use the Reevaluate Watch Expression command in the view's shortcut menu to evaluate the watch expression again.