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[求助] 在看例子时有几个问题看不懂

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发表于 2012-6-20 08:59:43 | 显示全部楼层 |阅读模式
新手,在看netlogo自带的例子时,有几行程序看不懂,希望高手能够指点。
' X6 p4 E- }% q0 X7 G/ l. c' enetlogo自带的social science--traffic grid这一例子当中,8 o7 y2 {; f! T0 w3 ^/ t( E. d
globals/ n! V* w+ [$ v* G
[
& _1 G  Y3 S! U& u1 F  grid-x-inc               ;; the amount of patches in between two roads in the x direction* f1 r7 @, f/ z0 Z% Q
  grid-y-inc               ;; the amount of patches in between two roads in the y direction4 B7 e+ q& c9 a/ _
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
) _4 \1 d% o! r8 U; A- M                           ;; it is to accelerate or decelerate( a* `4 k) T& W7 K
  phase                    ;; keeps track of the phase
3 [; V; y  y% f! I6 T5 c  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure- P8 q* H& N3 m& `7 G, a' z& H
  current-light            ;; the currently selected light  p, B5 S3 @6 Y) z

. x* ]  m9 O- y4 c* H  ;; patch agentsets
# s& v4 S. }" Q! A$ N9 N( a9 ]  intersections ;; agentset containing the patches that are intersections$ ], }; b4 W( r
  roads         ;; agentset containing the patches that are roads
! \& b+ p3 k7 J9 l& C/ o. Z$ _]  [2 E) z3 \$ N5 W) n. y# |

7 a; J/ y, H. h& U3 xturtles-own
6 ]0 R. u) z# H) y[
( L  p/ M/ Z: h' {" ?$ ]  speed     ;; the speed of the turtle2 k( N) S" n7 h- [6 Z' d
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
* e- c2 k# a1 b+ y6 U  wait-time ;; the amount of time since the last time a turtle has moved
: i! B/ N& D0 C! |' \: y]- ~8 ]# C5 `1 f  d6 b. B

# c) W1 N& z$ p- @, v) R+ Gpatches-own. F1 p3 |8 F) B1 N4 H5 W1 ]
[
3 P* C. k3 O; h) p1 k& h; S  intersection?   ;; true if the patch is at the intersection of two roads
* v1 q/ j5 n% F9 U- _/ C  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.) {: H, p+ B8 U4 H* m2 {; x3 V: ]/ o
                  ;; false for a non-intersection patches.
& u# `  [+ ]$ K% c; N. e  my-row          ;; the row of the intersection counting from the upper left corner of the8 Z% p9 q1 I& Q) I+ Q, x
                  ;; world.  -1 for non-intersection patches.6 V, Z( m& p9 X+ g
  my-column       ;; the column of the intersection counting from the upper left corner of the7 ]+ e! N, ?' m
                  ;; world.  -1 for non-intersection patches.
7 `6 R* N4 I' I# @4 z* e4 e7 Z5 Q  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
. M: X& ]. |* {5 h, i  auto?           ;; whether or not this intersection will switch automatically.
7 D! r8 Y! N/ o+ s9 S                  ;; false for non-intersection patches.) S1 a( y/ S5 h6 w& t6 n' L' s
]
* G8 _- o3 k" \, j( C# b
( Y3 |5 r8 H* {: J
" Z* W# B/ v+ n3 ^1 Z7 j8 x4 y;;;;;;;;;;;;;;;;;;;;;;
9 q0 @7 T, T- M" Y8 M# Z2 ?- D;; Setup Procedures ;;
+ s: b& A$ A  i/ t+ f: Q8 H;;;;;;;;;;;;;;;;;;;;;;" ^" P# Y9 e& g* L7 c) v" [

4 Z% d& b5 u' i4 q;; Initialize the display by giving the global and patch variables initial values.# F8 ?+ n, M2 Q8 m
;; Create num-cars of turtles if there are enough road patches for one turtle to
8 V) k, l1 v" R/ m: k;; be created per road patch. Set up the plots.
' p- o* @. G6 ^- G9 h0 E: qto setup6 n) q, h( I5 |! p* I8 }
  ca
7 a( @0 ^' x! w  setup-globals
0 o/ Z/ \' h/ s: C, X  j) l( b7 @4 q7 `
  ;; First we ask the patches to draw themselves and set up a few variables
5 f( m3 s9 T5 B! [1 A  setup-patches
3 }# C' H5 e7 v( [# d( l  make-current one-of intersections" {/ u/ H  \* H3 F( w, J
  label-current
* k: @( F. p0 {9 Q* Z0 f3 [2 D; N: r/ T1 v0 E* p* t: Y* l
  set-default-shape turtles "car"1 o% {% g2 T  O, |! F

- c0 A5 a7 v, a5 c# c1 h  if (num-cars > count roads)3 i( _+ `0 S9 a  q. p! M
  [) n- B2 `/ l9 ]- s% |
    user-message (word "There are too many cars for the amount of "
0 w) c6 N& M1 c                       "road.  Either increase the amount of roads "
: ^6 {5 c2 v* C/ ~4 p                       "by increasing the GRID-SIZE-X or "
$ o1 D0 e4 N; [5 }1 X7 z. o6 l                       "GRID-SIZE-Y sliders, or decrease the "" z2 j9 p" u! H% Q
                       "number of cars by lowering the NUMBER slider.\n"" l- q$ w5 a0 n- r, m1 D8 |
                       "The setup has stopped.")
; c* o0 n8 b% A: M. K) N- L    stop* C3 h* z: Y) `" h3 D
  ]
) \7 b: u4 k; R6 }3 W; i! {( O/ h/ n* g9 z/ {; s* a' o5 N$ r) w
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color1 f) [2 E" ^6 Z3 }
  crt num-cars3 x; F7 b) q0 {
  [
4 `3 |: Z$ N; N7 f& q$ \    setup-cars
$ k5 m0 c( a* s+ l! ?' A, m* S    set-car-color
7 S$ T- H* f/ Z2 r, [    record-data* ^2 O3 O* X  H7 I
  ]
' M% ~6 p+ r/ H  U. ]5 o
, e  o! S) b1 F! B% ]9 W0 m  ;; give the turtles an initial speed
% S) x: I0 Q' I7 l  ask turtles [ set-car-speed ]0 B1 C- n) u# M" J% f
( a( M; N  a' @3 D- `
  reset-ticks8 f( c7 S8 ~% G& B8 f) \
end, J  T( Z& e! F0 Z! ^

) J' c2 C, r1 W# k# `6 c;; Initialize the global variables to appropriate values0 X: f. n  A: i% @: h
to setup-globals
3 Z+ K8 q4 s' x+ p3 n: J  set current-light nobody ;; just for now, since there are no lights yet
; X6 p0 I3 ?9 ^, b7 @. N: v  set phase 0
" p! q$ N" \  W/ D! ?, n  set num-cars-stopped 0
! \: N+ U- i6 ?) H/ T4 y+ ]1 l  set grid-x-inc world-width / grid-size-x2 T* H4 y# @3 S: b( |
  set grid-y-inc world-height / grid-size-y+ K9 M+ H7 G7 N# T- ?3 C8 o$ W

$ J5 R+ p' W. `. ]7 _9 L$ V. Z9 i  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary1 b+ `2 d: s. h- p2 _
  set acceleration 0.099
( {8 n! t; G) u; |9 w! M1 Yend
, A( K* E+ p' b0 o. V
- ]. j% C- o6 o7 l( ~, @& g# e;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
+ j. K& t' P- D! v, i;; and initialize the traffic lights to one setting
/ ~) m! k: R; m" m" sto setup-patches* s* x' x2 n/ V5 R+ A+ y
  ;; initialize the patch-owned variables and color the patches to a base-color' B8 u3 v( D9 ^
  ask patches
6 W$ X& V# Y: K* k, l  e  [/ U9 `; {: `+ ^; }# v, x3 |
    set intersection? false) h6 e, U9 o9 s# D' \$ s4 h9 d  u6 U
    set auto? false; x$ s! |9 l' Q! @; G+ v
    set green-light-up? true
0 b1 |2 Q2 `) W, d$ [    set my-row -1. {3 O* [4 f6 n; ^0 p) D
    set my-column -1
, P7 z+ ~4 ^3 E5 w; `( E5 V/ q: e/ O    set my-phase -12 K' {* z3 `. o  @  v+ {
    set pcolor brown + 38 U! ]$ X0 a3 Y( I
  ]
, ^. j5 k+ F8 Q( w- G
! ]; }9 m# |% b/ ?4 E  e. k  ;; initialize the global variables that hold patch agentsets# _2 m7 a% \8 j. [% X2 f" K2 X
  set roads patches with
8 A, v- w( C- ~; c' Z% e    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or+ l- x$ Z: `  i3 _
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]0 s. o, n5 T! D$ w3 M
  set intersections roads with
4 p. S) v/ H6 {    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
2 F2 Y: u5 L* F, I    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]7 Q" A) Y, b8 C  V$ \+ a

8 W% t& G8 L" h+ O+ U. G  ask roads [ set pcolor white ]
+ v& h/ Q, [2 @$ c/ C# N    setup-intersections) p) s- H0 ]2 G3 y# e
end3 a9 y# B0 o4 x" P6 N1 k8 `6 k, d
其中定义道路的句子,如下所示,是什么意思啊?( B, W4 H  `( k7 \+ Z; x
set roads patches with& ]% I$ w! r/ ^0 v. l9 z$ U
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or! I, S$ r' Y$ c+ ?. ]
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]! ~* w2 \2 Q. z( r3 X/ j  h
谁能帮我解释一下[(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0)是什么意思吗?
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