I thought I needed these for this bouncing-ball demo:
def (bounce screen)
with (w (width screen)
h (height screen)
cx 16
cy 16
dx 12
dy 19)
while 1
clear screen
ring screen cx cy 16 3 5
cx += dx
cy += dy
when (or (cx > w) (cx < 0))
set dx 0-dx
when (or (cy > h) (cy < 0))
set dy 0-dy
for _ 0 (< _ 100) ++_ # delay
No matter how I adjusted the delay I couldn't get rid of the jitter. So
I built a double-buffered version:
(bounce2 . [def (bounce2 screen)
with (w (width screen)
h (height screen)
cx 16
cy 16
dx 12
dy 19
screen2 (new_screen (columns screen)
(lines screen)))
while 1
clear screen2
ring screen2 cx cy 16 3 5
cx += dx
cy += dy
when (or (cx > w) (cx < 0))
set dx 0-dx
when (or (cy > h) (cy < 0))
set dy 0-dy
blit screen2 screen
for _ 0 (< _ 100) ++_]) # delay
But it didn't make a difference! Turns out nothing will help you when
successive frames are too far apart. This is the correct tweak to
`bounce`:
- dx 12
- dy 19)
+ dx 1
+ dy (/ 19 12))
Still, we'll keep double-buffering around for the future.
The Mu shell has no string literals, only streams. No random access,
only sequential access. But I've been playing fast and loose with its
read pointer until now. Hopefully things are cleaned up now.
Like parenthesize, I'm copying tests over from https://github.com/akkartik/wart
Unlike parenthesize, though, I can't just transliterate the code itself.
Wart was operating on an intermediate AST representation. Here I'm all
the way down to cells. That seemed like a good idea when I embarked, but
now I'm not so sure. Operating with the right AST data structure allowed
me to more easily iterate over the elements of a list. The natural recursion
for cells is not a good fit.
This patch and the next couple is an interesting case study in what makes
Unix so effective. Yes, you have to play computer, and yes it gets verbose
and ugly. But just diff and patch go surprisingly far in helping build a
picture of the state space in my brain.
Then again, there's a steep gradient of skills here. There are people who
can visualize state spaces using diff and patch far better than me, and
people who can't do it as well as me. Nature, nurture, having different
priorities, whatever the reason. Giving some people just the right crutch
excludes others.
Kartik K. Agaram