DO(OPCS)		Optical Printer Control System		DO(OPCS)

        do - repeat commands

	do [count] [commands]
	do until (expr) [commands]

	do 12  rep 15 pro -5
	       ^These commands repeat 12 times  from left to right.

	do until (cam>=45) rep 15 pro -5
	         ^Loop until camera counter reaches 45 or greater.

        Repeat commands. Commands that follow the DO command up to the end of
	line are repeatedly executed the number of times specified by [count].

	If 'DO UNTIL (expr)' is used, looping continues until (expr) is true. 
	DO commands can be nested within a line. That is to say, 2 DO commands
	can appear on the same line:

		do 4  seek 10  do 8 rep 1 pro -1
		         |        |
		         |        These loop 32 times; the 'DO 4' loop
		         |        executes the 'DO 8' loop 4 times.
		         These loop 4 times

	In the case of do until (expr), usually (expr) is a conditional
	expression that compares one of the counters to a value, eg:

	 do until (cam=12) ..  # until cam counter is 12
	 do until (cam>=12) .. # until cam counter greater than or equal to 12
	 do until (pro>200) .. # until main projector counter greater than 200

	Run three 5 frame cycles of a moving projector image:

	    rat 1 1 do 3 rep 5 pro -5
	                 ^ These repeat 3 times from left to right.

	Run twelve 4-frame cross dissolves on every 8th projector image, effectively
	'weaving' still frames from an otherwise slow-motion moving projector image:

	    do 12 dxo 4 cam 4 cam -4 pro 8 dxi 4  cam 4
	          ^ These repeat 12 times

	Run a script file 7 times:

	    do 7 run
	         ^ This script is executed 7 times
	Gregory Ercolano, Los Feliz California 12/16/89
© Copyright 1997 Greg Ercolano. All rights reserved.