Computer Music (MUSC 216)
Blair School of Music
Vanderbilt University

Interactor Tutorials: Operators and Statements

Interactor uses a GUI language (Graphic User Interface) instead of a traditional "computer-eze" language such as C++. An interactor "program" consists of a series of OPERATORS like you used in SYD. However, instead of connecting the OPERATORS together by drawing lines between then, the OPERATORS are placed in STATEMENTS (see the example below where there are 2 STATEMENTS).These STATEMENTS tell the computer how to respond to incoming EVENTS.

By combining one or more OPERATORS into a single logical STATEMENT, the user can create an INSTRUCTION telling the computer what to do when a certain EVENT occurs. Each OPERATOR in a STATEMENT will be either TRUE or FALSE when it finishes performing its task. If an operator is true, it will cause the next operator in the statement to execute. Some operators (called Action Operators) are always true. Other operators (known as Conditional Operators) are true or false depending on the outcome of a test specified by the operator.

OPERATORS are grouped together in a single line which forms a logical STATEMENT. STATEMENTs are grouped together into a kind of SUBROUTINE called a SCENE.

Here is an Interactor SCENE with two STATEMENTs. Each STATEMENT has two OPERATORs:

In this scene, the 1st operator in each statement is a CONDITIONAL OPERATOR. The 2nd operator in each statement is an ACTION OPERATOR. The algorithm logic goes like this:

- IF the 'A' key is pressed, THEN turn on (play) C3
- IF the 'A' key is released, THEN turn off C3

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