SYNTAX(DOCS)            Optical Printer Control System          SYNTAX(DOCS)

    NAME
        syntax - syntax of OPCS numeric and math expressions

    OPCS COMMAND SYNTAX
        Many commands can appear on one line, and a line can be up to 128
        characters (or can wrap around the screen about one and a half times).
        Commands and arguments are separated by white space (spaces or tabs).

        Commands that allow a variable number of fixed arguments, e.g. SEEK,
        RES, and RAT, they let you use '-' to skip arguments.

        Where appropriate, '>' can be used as a prefix to a numeric value
        to specify an absolute position in the context of frames to shoot,
        or motor positions to go to.

        Some commands expect frame specifications, which can be expressed in
        many different ways. Such a command is the 'CAM' command, and here are
        some valid frame specifications:

           cam 12                  # run camera 12 frames
           cam -5                  # run camera 5 frames in reverse
           cam 12'2                # run camera 12 feet 2 frames
           cam -15'0               # run camera in reverse 15 feet
           cam >34                 # send camera TO frame 34
           cam >-34                # send camera TO frame -34
           cam >-12'3              # send camera TO negative 12 ft 3 frms
           cam (3+12*12)           # run camera 147 frames
           cam (3+(3*sqrt(16)*12)) # same as above
           cam >(3+12*12)          # send camera TO frame 147

    MATH EXPRESSIONS    
        You can usually use math expressions in place of most numeric 
        arguments as long as the expression is ENCLOSED IN PARENTHESES,
        and DOES NOT CONTAIN EMBEDDED SPACES. Example:

            (3+(3*sqrt(16)*12))

        Math can be done on frame counter values:

            (cam+3)

        For a complete list of all built in math operations, execute:

             (?)

        The following lists some of the operations supported by the 
        math expression parser:

             /*** TYPICAL OPERATIONS ***/

             (3+4-2*12/6)       # add, subtract, multiply, divide
             (533%256)          # modulus
             (2^4)              # exponentiation (powers)

             /*** OPCS VALUES ***/
             cam   - camera counter value
             pro   - main projector counter value
             pro1  - main projector counter value 
             pro2  - aerial projector counter value

             /*** MATH FUNCTIONS ***/

             sqrt(),  log(),     exp(),
             sin(),   cos(),     tan(),
             asin(),  acos(),    atan(),
             atan2(), radians(), degrees()
             hex(), pi

             /*** NUMERIC EXPRESSIONS ***/
             -12           # negative 12
             +34           # positive 34
             0x3ff         # hex representation for 1023 decimal

    DIFFFERENT APPROACHES YIELD SIMILAR RESULTS
        With few exceptions, there are usually two ways to do anything in the
        OPCS software. The following examples show two possible ways to do 
        step printing:

        do 12 cam 1 pro 2  # take 1 frame of every second projector frame
        
        rat 2 1 rep 12     # same as above
        
        The following two examples show how to automate the wedging process:
        
        do 200 cam 2 pse   # shoots 2 frames with a keyboard pause inbetween
        
        cam 2              # hitting the F4 key each time will shoot 2 frames
                           # doing more or less the same as the above
        
    COMMAND LINE EDITING KEYS
        OPCS supports all of DOS's editing keys, such as F3 (retype a line but
        do not execute), LEFT and RIGHT ARROW keys for revealing characters 
        from the last line typed, INSERT and DELETE keys, etc. Refer to your 
        DOS manual for more on these editing keys and their use.

        In addition to the standard DOS editing keys, the F4 key is programmed
        by the OPCS software to RE-EXECUTE the last line typed with one key 
        press. This is useful for doing wedges, or situations where manual 
        stopping/starting is necessary.

    SHELL EXECUTION
        Part of the system philosophy is to allow the user to their own
        custom programs/scripts from within OPCS, just like DOS commands.
        You can execute DOS commands by prefixing the command with a
        'bang' (!), e.g.

                !  dir *.run  |  more

        You can also use (!) to QUOTE a dos command, so that OPCS commands
        can be mixed with the dos commands:

                cam 12 ! echo Shot 12 frames !  pro 12 ! echo DONE
                         -------------------             ---------
        The underlined commands are executed as DOS commands, the rest
        are executed as OPCS commands. Note how '!' turns DOS execution
        on and off throughout the line.

        This (!) technique is patterned after a similar technique used
        by programs that run under the UNIX operating system.

    ORIGIN
        Gregory Ercolano, Los Feliz California 12/15/89