BrightScript supports the following statement types (note that BrightScript is not case sensitive). The syntax of each statement is documented in more detail later in this chapter.
Rem <or> '
For / To / End For / Step / Exit For <or> Next
For Each / In / End For / Exit For <or> Next
While / End While / Exit While
Function / End Function / As / Return
Each line may contain a single statement. However, a colon (:) may be used to separate multiple statements on a single line.
The LIBRARY statement allows you to include your own BrightScript libraries (.brs files), which can then be utilized by your script. The LIBRARY statement(s) must occur at the beginning of a script, before any other statements, functions, operators, etc.
The system locates a library by searching the directory containing the current script, as well as the
SYS:/script-lib/ directory. Note that the
Run() function does not currently change the path of a LIBRARY statement to that of the called script (i.e. the system will continue searching the directory of the caller script). On the other hand, running a script directly from the BrightSign shell does modify the library search path to that of the called script.
The first statement will include a library in the same folder as the script, while the second will include a library in a sub-folder.
The following statement will include the bslCore.brs library, which has some useful BrightScript features, from the
DIM Name (dim1, dim2, …, dimK)
DIM (“dimension”) statement provides a shortcut for creating roArray objects. It sets the variable Name to type “roArray”. It can create arrays of arrays as needed for multi-dimensionality. The dimension passed to
DIM is the index of the maximum entry to be allocated (i.e. the array initial size = dimension+1), though the array will be resized larger automatically if needed.
The following two lines create identical arrays.
The expression x[a,b] is equivalent to x[a][b].
The following script demonstrates useful operations on a DIM array.
variable = expression
The assignment statement (“=”) assigns a variable to a new value.
In each of the following lines, the variable on the left side of the equals operator is assigned the value of the constant or expression on the right side of the equals operator.
END statement terminates script execution normally.
STOP statement interrupts script execution, returns a “STOP” error, and invokes the debugger. Use the
cont command at the debugger prompt to continue execution of the script or the
step command to execute a single step in the script.
GOTO statement transfers program control to the line number specified by
GOTO label statement results in a branching operation. A
label is an identifier terminated with a colon on a line that contains no other statements or expressions.
RETURN statement returns from a function back to its caller. If the function is not type Void,
RETURN can also return a value to the caller.
PRINT [#output_object], [@location], item list
The PRINT statement prints an item or list of items in the console. The item(s) may be strings, integers, floats, variables, or expressions. An object with an ifInt, ifFloat, or ifString interface may also be printed. If the
output_object is specified, this statement will print to an object with an ifStreamSend interface.
If the statement is printing a list of items, the items must be separated with semicolons or commas. If semicolons are used, spaces are not inserted between printed items; if commas are used, the cursor will automatically advance to the next print zone before printing the next item.
Positive numbers and zero are printed with a leading space (without a plus sign). Spaces are not inserted before or after strings.
Each print zone in the following example is 16 characters wide. The cursor moves to the next print zone each time a comma is encountered.
In some cases, semicolons can be dropped. For example, the following statement is legal:
A trailing semicolon overrides the cursor-return so that the next
If the console you are printing to has the ifTextField interface, you can use the
@ character to specify where printing will begin.
Whenever you use
PRINT @ on the bottom line of the display, an automatic line-feed causes all displayed lines to move up one line. To prevent this from happening, use a trailing semicolon at the end of the statement.
This statement moves the cursor to the specified position on the current line (modulo the width of the console if the TAB position is greater than the console width).
Note the following about the
TABstatement may be used several times in a
- No punctuation is required after a
- Numerical expressions may be used to specify a
TABstatement cannot be used to move the cursor to the left.
- If the cursor is beyond the specified position, the
TABstatement is ignored.
This statement returns an integer that indicates the current cursor position from 0 to the maximum width of the window. This statement requires a dummy argument in the form of any numeric expression.
FOR / END FOR
FOR counter_variable = initial_value TO final_value STEP increment / END FOR <or> NEXT
FOR statement creates an iterative loop that allows a sequence of program statements to be executed a specified number of times.
increment can be any expression. The first time the
FOR statement is executed, these three variables are evaluated and their values are saved; changing the variables during the loop will have no affect on the operation of the loop. However, the
counter_variable must not be changed, or the loop will not operate normally. The first time the
FOR statement is executed, the counter is set to both the value and type of the
At the beginning of each loop, the value of the
counter_variable is compared with the
final_value. If the value of the
counter_variable is greater than the
final_value, the loop will complete and execution will continue with the statement following the
END FOR (or
NEXT) statement. If, on the other hand, the counter has not yet exceeded the
final_value, control passes to the first statement after the
FOR statement. If increment is a negative number, the loop will complete when the value of the
counter_variable is less than the
When program flow reaches the
END FOR (or
NEXT) statement, the counter is incremented by the specified increment amount (or decremented if increment is a negative value). If the
STEP [increment] language is not included in the
FOR statement, the increment defaults to 1.
EXIT FOR to exit a
FOR block prematurely.
The following script decrements
i at the beginning of each loop until it is less than 1.
FOR EACH IN / END FOR
FOR EACH item IN object / END FOR <or> NEXT
FOR EACH statement can iterate through a set of items in any object that has an ifEnum interface (i.e. an enumerator). The
FOR block is terminated with the
END FOR (or
NEXT) statement. Objects that are ordered intrinsically (such as roList) are enumerated in order, while objects that have no intrinsic order (such as roAssociativeArray) are enumerated in apparent random order. It is possible to delete entries as they are enumerated.
EXIT FOR to exit a
FOR block prematurely.
The following objects can be enumerated: roList, roArray, roAssociativeArray, roMessagePort.
The following script iterates over an associative array in random order, prints each key/value pair, then deletes it.
Nesting FOR EACH Statements
FOR EACH statement can only track one pointer per object instance, so nesting
FOR EACH loops that iterate on the same object may cause the series to terminate prematurely:
To work around this limitation with associative arrays, copy the keys to an array and iterate on the array in the nested
FOR EACH loop:
WHILE / EXIT WHILE
WHILE expression / EXIT WHILE
WHILE loop executes until the specified expression is false. Use the
EXIT WHILE statement to exit a
WHILE block prematurely.
IF / THEN / ELSE
IF expression THEN statements [ELSE statements]
This is the single-line form of the IF THEN ELSE statement; see the next section for more details about the block form of the IF THEN ELSE statement.
IF statement instructs the interpreter to test the following expression. If the expression is True, control will proceed to the statements immediately following the expression. If the expression is False, control will jump to either the matching
ELSE statement (if there is one) or to the next program line after the block.
THEN is optional in the above and similar statements. However,
THEN is sometimes required to eliminate ambiguity, as in the following example
Block IF / ELSEIF / THEN / ENDIF
The block (i.e. multi-line) form of IF / THEN / ELSE has the following syntax:
Function() As Type / End Function
Function name(parameter As Type, …) As Type
Each function has its own scope.
A function is declared using the
Function() statement. The parentheses may contain one or more optional parameters; parameters can also have default values and expressions.
The type of each parameter may be declared. The return type of the function may also be declared. If a parameter type or return type is not declared, it is Dynamic by default. Intrinsic types are passed by value (and a copy is made), while objects are passed by reference. The
Sub statement can be used instead of
Function as a shortcut for creating a function with return type Void.
A parameter can be one of the following types:
The function return can be one of the following types:
If a function is called from an associative array, then the local variable
m is set to the associative array in which the function is stored. If the function is not called from an associative array, then its
m variable is set to an associative array that is global to the module and persists across calls.
m identifier should only be used for the purpose stated above: We do not recommend using
m as a general-purpose identifier.
A function without a name declaration is considered anonymous.
The following is a simple anonymous function declaration:
Anonymous functions can also be used with associative-array literals: