Eval (EVAL)

The eval operator creates an action that executes defined program code in the lsFusion language. Program code is defined as a property whose value should belong to the string class. This is implemented using an action which takes a line of code as an argument.

The code that is passed to an action must be a sequence of statements. It is assumed that one of these statements will create an action named run (it is this action that will be executed).

Action execution

This operator can also execute a single action (rather than a set of statements): in this case the code should be a sequence of action operators and local property declarations. To refer to the parameters of the action, you can use the special character $ and the parameter number (starting from 1).

Executable code restrictions

In the current implementation, executable code must not contain statements that modify existing objects in the system. For example, you cannot add events or data and materialized properties, extend existing objects, etc.

Language

To declare an action that executes program code, use the EVAL operator.

Examples

// source code consisting of one statement is specified with a string constant
addProperty  { EVAL ACTION 'MESSAGE \'Hello World\''; }  

// a property to which the user can enter the source code
code 'Source code' = DATA BPSTRING[2000] ();

// the action executing this code              
execute 'Execute code'  { EVAL code(); }