Operators

Operators are used to perform comparisons and mathematical operations on the terms of an expression. Operators are used between values or expressions in the general form value1 OP value2. Some operators only accept values of a certain type. If the value for a variable is not a type supported by the operation, the operation will fail.

Mathematical Operators

String Operators

Comparison Operators

Table 3-3: Mathematical Operators
Operator	Description	Types Accepted
+	Addition: Add value1 to value2.	variables, numbers
-	Subtraction. Subtract value2 from value1	variables, numbers
/	Division. Divide value1 by value2	variables, numbers
*	Multiplication. Multiply value1 by value2	variables, numbers
MOD	Modulus. Returns the integer remainder of dividing value1 by value2	variables, numbers
^	Raise to the Power Of. Returns value1 raised to the power value2	variables, numbers

Table 3-4: String Operators
Operator	Description	Types Accepted
+	String concatenation. 'String1' + 'String2' creates 'String1String2'.	variables, numbers, strings
CONTAINS	String contains. value1 CONTAINS value2 returns true if value2 is found in value1, returns false otherwise.	variables, strings

Table 3-5: Comparison Operators

Table 3-5: Comparison Operators
Operator	Description	Types Accepted
GT	Greater Than. TRUE if value1 is greater than value2	variables, numbers
GE	Greater Than or Equal To. TRUE if value1 is greater than or equal to value2	variables, numbers
LT	Less Than. TRUE if value1 is less than value2	variables, numbers
LE	Less Than or Equal To. TRUE if value1 is less than or equal to value2	variables, numbers
EQ	Equality. TRUE if value1 is equal to value2	variables, numbers, strings
NE	Not Equal To. TRUE if value1 is NOT equal to value2	variables, numbers, strings
ISTYPE	TRUE if the data type of the variable specified by value1 corresponds to value2, a string representing the variable type. value2 can be one of the following string literals: 'BOOL', 'STR', 'INT', 'DOUBLE', or 'UNDEF'.	variables, numbers, strings

Logical Operators

ION Script's logical operators are listed in the following table. Note that values used with logical operators can be values, variables, or expressions, but they must evaluate to a boolean value.

Table 3-6: Logical Operators

Table 3-6: Logical Operators
Operator	Description	Types Accepted
AND	Logical AND. value1 AND value2 returns true if both value1 and value2 evaluate to true. Returns false otherwise.	Boolean value or variable, or expression that evaluates to a boolean
OR	Logical OR. value1 OR value2 returns true if either value1 or value2 evaluates to true. Returns false otherwise.	Boolean value or variable, or expression that evaluates to a boolean
NOT	Logical negation. NOT value returns true if value is false and returns false if value is true.	Boolean value or variable, or expression that evaluates to a boolean

The following are examples of valid expressions using the logical operators. For these examples, assume

$BOOL1 = true  
$BOOL2 = false  
$A = 1  
$B = 2
 


 
Table 3-7: Logical Operator Results 
  



   
Table 3-7: Logical Operator Results 
  


       
Type of operand
  


     
Expression
  


     
Result
  



       
Boolean variables
  


     
$BOOL1 AND $BOOL2
  


     
false
  



       
$BOOL1 OR $BOOL2
  


     
true
  



       
Boolean values
  


     
true AND false
  


     
false
  



       
true OR false
  


     
true
  



       
Expressions that evaluate to booleans
  


     
($A NE $B) AND ($A EQ 1)
  


     
true
  



       
($A EQ 5) OR ($B EQ 5)
  


     
false
  



       
NOT ($A EQ $B)
  


     
true
  



       
$BOOL1 AND ($A EQ 1)
  


     
true
  





  

 
Operator Precedence
  


 
The following table lists the ION Script operators in order of precedence. All operators are left associative, meaning that operators of equal precedence (such as + and -) are evaluated from left to right.
  


 
Table 3-8: Operator Precedence 
  



   
Table 3-8: Operator Precedence 
  


       
Precedence
  


     
Operators
  



       
Highest


  

 
Lowest
  


     
( )
  



       
- (negation)
  



       
^
  



       
NOT
  



       
*, /, MOD
  



       
+, - 
  



       
 GT, GE, LT, LE, CONTAINS, ISTYPE
  



       
AND
  



       
OR
  



       
EQ, NE
  







  


 
Grouping Expressions With Parentheses
  

 
Parentheses are used in ION Script to control the order of evaluation of expressions. Expressions that are contained inside parentheses are evaluated first by ION Script. When multiple sets of parentheses are nested within one another, the expression contained in the innermost set of parentheses is evaluated first.
  

 
For example, consider the following code:
  

<ION_IF EXPR="$Month EQ 'April' OR $Month EQ 'May'   
   AND $Temp EQ 70 ">  


 
This statement is equivalent to the following:
  

<ION_IF EXPR="$Month EQ 'April' OR   
   ($Month EQ 'May' AND $Temp EQ 70)">  


 
If your intent was to require $Temp to be 70, but allow the $Month to be April or May, you would need to override the precedence as follows:
  

<ION_IF EXPR="($Month EQ 'April' OR $Month EQ 'May') AND   
   $Temp EQ 70 ">  


 
 


   Tip

   It is good programming practice to use parentheses to control the order of evaluation, even when not technically necessary. This ensures that your expressions are being evaluated in the order you intended, and makes your code more readable.


  




 
Examples
  

 
The following table gives several examples of the order in which expressions are evaluated in ION Script:
  


 
Table 3-9: Expression Evaluation 
  



   
Table 3-9: Expression Evaluation 
  


       
Expression
  


     
Result
  



       
10 * 5 - 2
  


     
48
  



       
10 * (5 - 2)
  


     
30
  



       
3 + 4 * 2 ^ 2 / 2
  


     
11
  



       
(3 + (4 * 2) ^ 2 / 2)
  


     
35
  







  

 





  IDL Online Help (March 06, 2007)

Type of operand	Expression	Result
Boolean variables	$BOOL1 AND $BOOL2	false
Boolean variables	$BOOL1 OR $BOOL2	true
Boolean values	true AND false	false
Boolean values	true OR false	true
Expressions that evaluate to booleans	($A NE $B) AND ($A EQ 1)	true
	($A EQ 5) OR ($B EQ 5)	false
	NOT ($A EQ $B)	true
	$BOOL1 AND ($A EQ 1)	true

Precedence	Operators
Highest Lowest	( )
	- (negation)
	^
	NOT
	*, /, MOD
	+, -
	GT, GE, LT, LE, CONTAINS, ISTYPE
	AND
	OR
	EQ, NE

Expression	Result
10 * 5 - 2	48
10 * (5 - 2)	30
3 + 4 * 2 ^ 2 / 2	11
(3 + (4 * 2) ^ 2 / 2)	35