- Local variables
- Compiling the expression
- Using a procedure of external component
- Dynamic code
EvaluateExpression (Function) In french: EvalueExpression Evaluates the value of an expression built in a character string.
// Evaluate a formula
x,y are real
x = 1.5
y = 5
Trace(EvaluateExpression("cos(x)+sin(y)"))
Syntax
<Result> = EvaluateExpression(<Expression>)
<Result>: Any type - If the expression compiles without any errors, result of the expression.
- If the expression fails to compile, if it does not return a value or if an error occurs during the evaluation, it triggers a fatal error.
<Expression>: Character string Expression to evaluate. Remarks Local variables The local variables of the current process can be used directly in the expression. Compiling the expression The code is recompiled whenever EvaluateExpression is called. To avoid the compilation step, you can use Compile and Execute to build the code of a procedure, compile it once and run it several times. In this case, you will lose the ability to directly use local variables of the current process which will need to be replaced by parameters in the procedure. Using a procedure of external component The code is recompiled whenever EvaluateExpression is called. The call to a procedure of external component must name this procedure with its full name.
EvaluateExpression("MyComponent.MySet.MyProcedure()"))
Dynamic code The constants cannot be used in the dynamic code (defined by the CONSTANT keyword). When using constants in a code, all the occurrences of the constants are replaced with their value during the compilation in the editor but the correspondence between the name of constants and their value is not "embedded" in the application. Therefore, the dynamic compilation cannot use the constants. Let's see two alternatives: 1 - Use variables instead of constants: 2 - In the string containing the code that must be compiled dynamically, replace the name of the constant by its value:
sCode is string
// In the string containing the code that will be compiled dynamically
// instead of leaving the name of the constant:
sCode=[
Info(CST_Name)
]
// Replace the name of the constant by its value
sCode = Replace(sCode, "CST_Name", CST_Name, WholeWord + IgnoreCase)
// The code can be compiled now
IF Compile("DynProc", sCode) <> "" THEN
Error("Error while compiling the dynamic procedure: ", ...
ErrorInfo())
ELSE
// Then it can be run
WHEN EXCEPTION IN
ExecuteProcess("DynProc", trtProcedure)
DO
Error("Error while running the dynamic procedure: ", ...
ExceptionInfo())
END
END
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