6.1-Operators

String Operators: The following operators work with strings: <, >, =, <>, <=, >=, +

Function References: The = and <> operators work on variables that contain function references and function literals.

Logical and Bitwise Operators

The AND, OR, and NOT operators are used for logical (Boolean) comparisons if the arguments for these operators are Boolean:

if a=c and not(b>40) then print "success"

On the other hand, if the arguments for these operators are numeric, they will perform bitwise operations:

x = 1 and 2   ' x is zero
y = true and false  ' y is false

When the AND or OR operator is used for a logical operation, only the necessary amount of the expression is executed. For example, the first statement below will print "True", while the second statement will cause a runtime error (because "invalid" is not a valid operand for OR):

print true or invalid
print false or invalid

Dot Operator

The "." Dot Operator can be used on any BrightScript object. It also has special meaning when used on an roAssociativeArray object, as well as roXMLElement and roXMLList objects. When used on a BrightScript Object, it refers to an interface or method associated with that object. In the following example, IfInt refers to the interface and SetInt() refers to a method that is part of that interface:

i=CreateObject("roInt")
i.ifInt.SetInt(5)
i.SetInt(5)

Every object method is part of an interface. However, specifying the interface with the "." Dot Operator is optional. If the interface is omitted, as in the third line of the above example, each interface that is part of the object will be searched for the specified member. If there is a naming conflict (i.e. a method with the same name appears in two interfaces), then the interface should be specified.

Associative Arrays

When the "." Dot Operator is used on an Associative Array, it is the same as calling the Lookup() or AddReplace() methods, which are member functions of the roAssociativeArray object:

aa=CreateObject("roAssociativeArray")
aa.newkey="the value"
print aa.newkey

The "." Dot Operator is always case insensitive: For example, the statement aa.NewKey=55 will create the entry "newkey" in the associative array. To generate case-sensitive keys, instantiate an roAssociativeArray object and use the SetModeCaseSensitive() method.

Array and Function-Call Operators

The [ ] operator is used to access an array (i.e. any BrightScript object that has an ifArray interface, such as roArray and roList objects). It can also be used to access an associative array. The [ ] operator takes expressions that are evaluated at runtime, while the "." Dot Operator takes identifiers at compile time.

The ( ) operator can be used to call a function. When used on a function literal (or variable containing a function reference), that function will be called.

The following code snippet demonstrates the use of both array and function-call operators.

aa=CreateObject("roAssociativeArray")
aa["newkey"]="the value"
print aa["newkey"]

array=CreateObject("roArray", 10, true)
array[2]="two"
print array[2]
 
fivevar=five
print fivevar()
 
array[1]=fivevar
print array[1]()   ' print 5
 
function five() As Integer
   return 5
end function

Array Dimensions

Arrays in BrightScript are one dimensional. Multi-dimensional arrays are implemented as arrays of arrays. The [ ] operator will automatically map multi-dimensionality. For example, the following two fetching expressions are the same:

dim array[5,5,5]
item = array[1][2][3]
item = array[1,2,3]

Equals Operator

The = operator is used for both assignment and comparison:

a=5
If a=5 then print "a is 5"

Unlike the C language, BrightScript does not support use of the = assignment operator inside an expression. This is meant to eliminate a common class of bugs caused by confusion between assignment and comparison.

When assignment occurs, intrinsic types are copied, while BrightScript Objects are reference counted.