I'm looking for a more concise way to compare a variable to a range of numbers in Structure Text (ST) - st

Question

I am trying to find a more concise way to compare a variable to a range of numbers.
Currently I do:
IF int_variable=67 or int_variable=68 or int_variable=69 then...
Is there a way to write something like: IF int_variable=67 through 69 then
Thanks in advance.

Answer 1

If you really mean that if the variable is in range of those numbers, it's just simple as this. But in more complex situations you have no shortcuts, just use Jakobs method or similar.
IF int_variable >= 67 AND int_variable <= 69 THEN
//It is 67, 68, or 69
END_IF

Answer 2

You could for example use a for-loop, like:
FOR nCounter := 67 to 69 by 1 DO
IF int_variable = nCounter THEN
....
EXIT; // If you want to exit the loop
END_IF
END_FOR

Answer 3

If the comparisons are always integers (or an enumerated type) you can use a case statement.
CASE example_int OF
1,2: <do whatever you need to do>
4,5,7,8: <do other stuff>
ELSE
<do default case stuff>
END_CASE
If you need larger ranges you'll just have to use AND or nested IFs (nested IFs shown below)
IF example_int >= 2 THEN
IF example_int < 5 THEN
//in range 2 - 5
ELSIF example_int <= 10 THEN
//in range 6 - 10
END_IF
END_IF
Remember to be mindful of the end points. If you forget the "or-equals" portion in either of the IF statements above, it changes the range

Answer 4

There is no other way to check if the condition is ok like you want to do. In ST, you can code Library & function, if you have too much condition, you can code a library who resolve your problem. But it's useless because ST allow to order code to be readable. Like below :
IF (n>=0) AND (n<=20) OR
(n>=32) AND (n<=45) THEN
// Do this
ELSE
// Do that
END_IF ;
But you can call a function or library to fill a boolean var with TRUE or FALSE. You will just need to test the var in a logic loop.
//IN_aTestValues & aValueToTest are an Array of values
bVarTest := TestCond( IN_aTestValues := aValueToTest );
If bVarTest THEN
// Do this
ELSE
// Do that
END_IF ;
You can also do :
bVar := bToTest = 67 AND
bToTest = 84 AND
bToTest > 47 AND
NOT (bToTest = 25) ;
IF bVar THEN
// Do this
Else
// Do That
END_IF ;