(Engine-Level Function)
| Description: | For use in expressions that perform Boolean logic. Using "TRUE" will make your code easier to read than using "1". |
| Returns: | With no parameters, returns the value, 1. If given a parameter, this function will return a 1 or 0 depending on whether the parameter evaluates to TRUE or FALSE. Always returns 0 if the parameter is Invalid. |
Usage:  |
Script or steady state. |
| Function Groups: | Logic Control |
| Related to: | False |
| Format: |
True[(TestExpr)] |
| Parameters: |
| TestExpr |
| Optional. Any expression that evaluates to a 1 or 0 value. If no parameter is provided, then there is no need to include the parentheses. |
| Comments: |
This function exists to make your code more readable. It is equivalent to PickValid(Cast(Parameter, 0) == 1, 0); For compatibility with the VTScada style guide, use all caps (TRUE and FALSE) when used as a constant. Capitalize only the first letter when used as a function call: True(test expression) and False(test expression). |
Examples:
Given the following code in a simple page:
[ Title = "OverviewLabel"; Color = "<FFFFFFFF>"; Y; ] Main [ ZText(100,100,Y ? "Y is true": "Y is false", 0,0); ZText(100,120,True(Y) ? "Y is true": "Y is false", 0,0); Return(Self); ]
Only the text at 100,120 will be shown. In the first call to ZText, Y is Invalid and therefore neither true nor false. The use of True(Y) in the second call to ZText ensures that the test always evaluates to true or false.
