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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。7 ?& G8 b2 J/ c/ v  ^3 u3 Z" G
netlogo自带的social science--traffic grid这一例子当中,
+ @- j% a2 K3 ~  \  `5 Fglobals
+ B  ?- |, u, p4 T. Y[$ Z1 L: P0 I% U6 [- [
  grid-x-inc               ;; the amount of patches in between two roads in the x direction7 M# }% f, Z3 ?1 Q6 M
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
5 B  W$ w- g) y  @6 g( ^3 ?$ e  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
* {2 ~9 F4 c) ^                           ;; it is to accelerate or decelerate% M' H* R/ e. L
  phase                    ;; keeps track of the phase
9 `' p8 v0 z# z' `% k  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
3 ?3 M- c8 b# }$ m  current-light            ;; the currently selected light
4 x! i- A2 l1 O7 v7 x: a. `
  c" Y& h. N2 o' e' E( P" l$ Z) U  ;; patch agentsets/ {( e' M) A1 _$ _5 K
  intersections ;; agentset containing the patches that are intersections  W" I7 _0 D  z2 `. ]/ J' s
  roads         ;; agentset containing the patches that are roads
* w% \& Z. g: p5 Y: E]
1 v/ [1 Y0 v) o) N5 \. l- O% L. Q) S0 z" l
turtles-own
' J2 t) X3 C, Q. R[+ D4 }9 A9 A0 o1 O' _6 K. z1 l
  speed     ;; the speed of the turtle
# r$ h7 }( U, h, Q/ x  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
6 j. l0 [) C" A" d  wait-time ;; the amount of time since the last time a turtle has moved
7 G5 R- j% n0 f' c$ m3 a3 h]
% ~, J- E9 W6 g( S! T& _9 `5 T' b4 a' G7 y0 |+ b4 v* _5 i* E! P7 ~
patches-own% [7 L5 B* S0 d, q4 J$ i
[
% F# g! A7 _$ Y  intersection?   ;; true if the patch is at the intersection of two roads
8 I! E9 A0 n' j/ t  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
* F% I- `) m3 @+ R; S! \$ Q                  ;; false for a non-intersection patches.
9 @1 N! X1 L# Y  my-row          ;; the row of the intersection counting from the upper left corner of the0 V+ F2 w" \) |, Q, R
                  ;; world.  -1 for non-intersection patches./ \: C) ]) [' Z$ y
  my-column       ;; the column of the intersection counting from the upper left corner of the" E, g6 m# t; V- A$ c/ ?& c
                  ;; world.  -1 for non-intersection patches.
5 D) g7 Y4 U  }1 D  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.! T: h9 ]5 [+ P. M& ~
  auto?           ;; whether or not this intersection will switch automatically.2 c# W* D1 g$ Y  w
                  ;; false for non-intersection patches.
0 _3 ]1 q" u8 W]
/ \5 [$ s5 O% t7 O! L! w
# l4 O9 W9 K% r) ~& e
6 S  k: o8 [- a% T- u;;;;;;;;;;;;;;;;;;;;;;
9 m2 I" m: n5 M* p;; Setup Procedures ;;+ F3 ~. b. G& B3 G' V
;;;;;;;;;;;;;;;;;;;;;;. k3 U8 x$ N( ^  o: B* s3 X
+ ^6 m7 q8 i% O* b. q# a0 j% i
;; Initialize the display by giving the global and patch variables initial values.
1 k# w3 C, t, ^7 W% E/ {. G;; Create num-cars of turtles if there are enough road patches for one turtle to. ^2 M  C# o$ w' N5 C
;; be created per road patch. Set up the plots.
: v5 ^. t8 q, @& ]2 U5 fto setup' j1 {& b7 P& Y  M8 c4 x
  ca3 o* C2 T. V1 p
  setup-globals
0 h; y& ]' W: u5 \) U* g( d, d, C
  ;; First we ask the patches to draw themselves and set up a few variables$ e: \: Z. x' u0 R7 p
  setup-patches
2 N# m$ j" u' R1 l5 K  make-current one-of intersections
  P& @5 `8 H9 z% z& s0 d  ~  label-current% A+ Q/ s+ w1 K' Y1 s3 V
" r0 `6 |0 w2 T) ~6 ~
  set-default-shape turtles "car"+ u) q( J4 q4 o
* [, h9 b2 l" t0 E, P. u$ @7 ?3 l
  if (num-cars > count roads)
! w$ V! j8 [4 p& a3 a: o, O  [
, A& ?" ~% V2 p8 I    user-message (word "There are too many cars for the amount of "
/ Q/ X1 L1 }" r/ o                       "road.  Either increase the amount of roads "1 j: s) a' U- d0 s+ T  R
                       "by increasing the GRID-SIZE-X or "
% F1 t5 G) M' U/ h2 {: u                       "GRID-SIZE-Y sliders, or decrease the "
5 }6 D2 t6 Z, T4 T8 J3 z                       "number of cars by lowering the NUMBER slider.\n"
/ P1 R3 E* b+ H8 n9 e( x                       "The setup has stopped."): h9 n$ ~/ b+ o: S+ A7 y9 W
    stop
+ z; L, D9 v4 P- r4 ?" `  ]3 X4 u: f" p: X$ w1 U

3 R* W* S1 T* A" E* J1 U: {0 c  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color8 T1 J4 [& `: I) ?
  crt num-cars
/ {' D- m5 s8 d5 n8 c6 A  [
. U% t$ z( Y( X8 a. ^" o    setup-cars
2 \, ?( @  H8 z+ o- m! r8 C4 f    set-car-color
1 D8 K( p7 V* @  J( v* T    record-data- |; P% f" z) h# {
  ]
: N+ D& n" ]# H1 n* j3 j7 t. e) M5 u1 t6 l: {% s, f. W
  ;; give the turtles an initial speed
* }7 p& u: ?3 k$ V  u2 [  ask turtles [ set-car-speed ]! F% X; c! C3 r. e  C6 g: l
0 p2 g! D: f2 y+ ]1 K( t7 v" g
  reset-ticks" B, o6 ?' s0 U2 X7 i5 P
end( k  a' [4 r' H* x8 D4 q$ L

$ A( _8 {  w& B8 ?;; Initialize the global variables to appropriate values
: m1 Q, D4 F8 B4 m7 b  k- [to setup-globals
3 H* S9 Y+ Q, Z  y' I/ \+ ~3 {, A  set current-light nobody ;; just for now, since there are no lights yet3 v4 H* \, F5 ^, [0 [4 N
  set phase 0/ h( ~, Y! X8 m' v
  set num-cars-stopped 0
  k4 ]4 `% ]4 t: C  set grid-x-inc world-width / grid-size-x! A4 X- W6 A) ^+ ~# Y( T
  set grid-y-inc world-height / grid-size-y4 O0 x) e. c2 l' P1 K" k

. r' ~  A! c' ]4 F. y  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
7 v5 R8 d$ e5 [) u! _  set acceleration 0.0999 }* o' G) e9 s, D
end0 g  z& K" A  d* U- Z' y% g3 m

% p7 P0 A0 v# I9 S0 ~  y( v' H& };; Make the patches have appropriate colors, set up the roads and intersections agentsets,( K" A- z2 I  `% ]0 X5 ^
;; and initialize the traffic lights to one setting
3 Q7 I- G! {, L  [to setup-patches* T5 g) j1 _5 C( y! U1 r' Q
  ;; initialize the patch-owned variables and color the patches to a base-color
5 S( U; X2 z3 t, d# @+ z/ H$ h' T/ n  ask patches
4 Y' B7 ~; C9 a) }9 w  [1 b1 t1 w0 l' u- S! y
    set intersection? false
4 {! W5 u- m* Y5 m; }: {/ J    set auto? false
! X: G: A' q1 |    set green-light-up? true
- @  z1 N2 t& I% J    set my-row -1$ l2 J& k" M9 ^* {8 R
    set my-column -1
# D* f3 Q3 x% I, l    set my-phase -1
5 p1 ]' b, Z; e4 p& i7 q    set pcolor brown + 3
2 P$ L) F, H% Z1 x6 X) g2 O+ K, G- }  ]$ @7 b# T8 Z9 t+ Y
+ ]9 z! v" O7 V' @  a2 j
  ;; initialize the global variables that hold patch agentsets" }' V* _& z' {. J4 `
  set roads patches with* S: C) Q7 C9 h, M. O
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or. d/ X9 K$ |) q2 u
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]& A" a+ O# `  a
  set intersections roads with; ]2 t9 K/ w8 V0 H% ]
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and& M# ^- _; f% o# y. k, z6 t
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]# u- ~8 P# v7 F+ z& w" p

# j# z5 t" |  U' d  ask roads [ set pcolor white ]) u0 T0 B1 ~7 D4 }( \7 Z- e- ~- E5 u
    setup-intersections( q, [1 H, P" [  g$ `! A' T8 p$ k4 D
end% j" k. H; @5 V+ Z
其中定义道路的句子,如下所示,是什么意思啊?
$ V) f" S) e; v1 O8 Y: ~% [. R set roads patches with
& p% e4 G4 R; T/ k    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
. L* h7 B: R9 U& p- M1 A    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]% Z! i& `  c9 O' V
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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