[0.24] Automated Guidance Computer

[bassgojoe]

It looks like the 0.23 package is compatible with 0.24. I also put the source up on github:

https://github.com/joevenzon/kerbal-agc

[weissel]

bassgojoe, what's the correct syntax for defining a function that does NOT take a parameter? (In this case I'm trying for a function that returns #t once and #f ever after, for example for the initial launch staging.)

(define (func junk) ...) works, but needs a junk value in the call.

(define (func) ...) complains that I need to add an argument.

(define func ...) does not work, from all I see it thinks 'func' is going to be a variable.

Common Lisp sidesteps that issue by having a 'defun' and 'defvar' (and 'defmacro', 'defconstant', 'defclass', 'defmethod', 'defparameter' and so on).

[bassgojoe]

The fact that (define (func) ...) doesn't work is probably a bug. But you can work around it:

(define (f x y ...) exp) is actually just converted into (define f (lambda (x y ...) exp))

So if you want to define a function without any variables you should be able to use the lambda syntax directly:

(define func (lambda () exp))

[bassgojoe]

Fixed in https://github.com/joevenzon/kerbal-agc/commit/8e4ef3e4c367c7585b8586f4c87b472bb0b645e3

[weissel]

(begin
	(define AGC.Status (list 1 88))
)

works.

(begin
((lambda ()
	(define AGC.Status (list 1 88))
))
)

does not work. It behaves as if AGC.Status was never defined, though introducing errors in the define line are detected and seem to indicate that the line is executed. Changing to some other command (e.g. a let with an if and an action group) also shows that the code is executes.

Since AGC.Status is about the only flexible output possibility (outside defining variables and dumping them by pressing "Debug") this does hamper code testing.

[weissel]

For e.g. calculating atmospheric density[1] at height raising Euler's Number to (/ -12502 5000) is needed. Also important is the natural logarithm.

[1] for finding terminal velocity. For intelligent speed control on the lower part of ascent, for example.

It would be good to be able to use the common trigonometric functions.

[bassgojoe]

(begin
	(define AGC.Status (list 1 88))
)

works.

(begin
((lambda ()
	(define AGC.Status (list 1 88))
))
)

does not work.

For the variable to exist in the parent scope you need to define it there and then set it inside your function:

(begin
(define AGC.Status 0)
((lambda ()
	(set! AGC.Status (list 1 88))
))
)

Edited August 25, 2014 by bassgojoe

[bassgojoe]

Transcendental functions have been added: https://github.com/joevenzon/kerbal-agc/commit/33d464409d28d6d7e1c61049a3cededcbb5033fa

and I updated the README.md with their names.

[weissel]

For the variable to exist in the parent scope you need to define it there and then set it inside your function

Adjusting mental model from "Magic variable that pre-exists, but must be written to with 'define' instead of 'set!'" to "If a top level AGC.Status variable is made to exist at the end of the pass (once per tick) through the program, the content is also shown in the output field --- this is the only magic. The variable does not exist if you don't create it."

Transcendental functions have been added: https://github.com/joevenzon/kerbal-agc/commit/33d464409d28d6d7e1c61049a3cededcbb5033fa

and I updated the README.md with their names.

Cool! Thank you! Now I only need to manage to wrangle monodevelop into submission ... and my next mission under computer control can start.

[bassgojoe]

I threw the compiled AGC.dll file in git since it's small, to save you the trouble of monodevelop:

https://github.com/joevenzon/kerbal-agc/tree/master/AGC/AGC/bin/Debug

Let me know how your missions go!

[hieywiey]

Hmm... Something tells me that that computer is homicidal... but I don't know what it is...