blob: 7c64e366fdf9ba538174434fbcc48f67bdc8888a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
#N canvas 6 61 602 516 10;
#X declare -lib Gem;
#X obj 14 66 gemwin;
#X obj 14 9 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 0 1
;
#X msg 48 10 create;
#X msg 55 33 destroy;
#X obj 14 93 gemhead;
#X obj 14 213 t a a;
#X obj 59 213 circle;
#X obj 14 283 scale 0.7;
#X obj 14 243 rotate 45 0 0 1;
#X obj 14 263 translate 2 0 1 0;
#X text 170 17 A tutorial on recursion in Gem;
#X text 170 37 (GPL) 2007 Claude Heiland-Allen <claude@mathr.co.uk>
;
#X text 170 77 A common idiom in Gem is to use the [repeat] object
found in the Zexy library \, to generate multiple copies of the same
object. Let's try using it to make our spiral.;
#X obj 14 183 separator;
#X obj 24 163 r \$0-recurse;
#X obj 68 133 v \$0-depth;
#X obj 14 113 t a b;
#X obj 68 113 f 16;
#X floatatom 91 96 5 0 0 2 max-depth - -;
#X obj 36 433 s \$0-recurse;
#X obj 14 313 t b a b;
#X obj 99 343 v \$0-depth;
#X obj 99 363 - 1;
#X obj 99 383 max 0;
#X obj 99 403 v \$0-depth;
#X obj 36 413 spigot;
#X obj 14 343 v \$0-depth;
#X obj 14 383 v \$0-depth;
#X obj 14 363 + 1;
#X text 170 127 First \, we need to limit the depth of the recursion
\, to avoid the dreaded "stack overflow" errors from both Pd and OpenGL.
We set the maximum depth before doing anything else in the Gem chain.
;
#X text 170 187 Next \, we draw the circle and set up the transformations
for the recursive call.;
#X text 170 227 Finally \, we check that we are within the allowed
depth \, and recurse (after decrementing the maximum depth).;
#X text 170 267 At first glance \, this recursive solution is much
less elegant than the iterative solution with [repeat] \, and it is
-- for non-branching structures. The power of recursion comes from
the ease with which branching structures can be created.;
#X obj 497 15 declare -lib Gem;
#X connect 1 0 0 0;
#X connect 2 0 0 0;
#X connect 3 0 0 0;
#X connect 4 0 16 0;
#X connect 5 0 8 0;
#X connect 5 1 6 0;
#X connect 7 0 20 0;
#X connect 8 0 9 0;
#X connect 9 0 7 0;
#X connect 13 0 5 0;
#X connect 14 0 13 0;
#X connect 16 0 13 0;
#X connect 16 1 17 0;
#X connect 17 0 15 0;
#X connect 18 0 17 1;
#X connect 20 0 26 0;
#X connect 20 1 25 0;
#X connect 20 2 21 0;
#X connect 21 0 22 0;
#X connect 22 0 23 0;
#X connect 23 0 24 0;
#X connect 23 0 25 1;
#X connect 25 0 19 0;
#X connect 26 0 28 0;
#X connect 28 0 27 0;
|
