Lego/Scheme
By Rusty Burchfield and Brent Hepburn
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Background
• Limited implementation of Scheme for the
standard firmware
• Developed at Indiana University by three
CS undergraduates
• Developed start to finish in three days
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Environment
• Petite Chez Scheme 6.1
– LegoScheme compiler
– LegoScheme source
• Lego Mindcontrol
– Visual Basic output from LegoScheme
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Features
•
•
•
•
10 concurrent tasks
Support for most built-in scheme functions
Support for lambda definitions
Functions defined for direct interaction
with RCX
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Limitations
• Requires Lego Mindcontrol
• Tail-recursive ONLY and without
parameters
• Limited support for bindings
• Only 8 functions
• Only 30 signed integers available
• Concurrency issues
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Example
(define task_zero
(lambda ()
(setup-sensor 1 'reflection 'percent)
(set-engine-direction "02" 'forward)
(set-engine-speed "02" 4)
(set-engine-on/off "02" 'on)
(task_one)
(task_two)
(task_three)))
(define task_one
(lambda ()
(let ((x (read-from-sensor 0)) (y (read-fromsensor 2)))
(if (= x #t)
(set-engine-on/off "02" 'off))
(if (= y #t)
(flip-engine-direction "02"))
(task_one))))
(define task_two
(lambda ()
(wait 500)
(flip-engine-direction "0")
(wait 200)
(flip-engine-direction "0")
(wait 500)
(flip-engine-direction "2")
(wait 200)
(flip-engine-direction "2")
(task_two))
(define task_three
(lambda ()
(let ((z (read-from-sensor 1)))
(if (> z 50) (play-system-sound 'fast-slideup) (task_three)))))
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Conclusion
• Difficult to use
– Many restrictions
– Hard to setup
• Lacking the power of Scheme
LEGO name and Symbol are registered
trademarks of the LEGO Group.
Resources
• References
– http://www.cs.indiana.edu/~mtwagner/legosch
eme/
– http://home.zonnet.nl/ericbrok/legomind/proje
cts/robo/mindcontrol.htm
• More Information
– http://www.cs.rit.edu/~bah5108/
LEGO name and Symbol are registered
trademarks of the LEGO Group.