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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。& b+ u' U$ Z" u1 h
netlogo自带的social science--traffic grid这一例子当中,
- Z2 e. z  t- r; F! f  A+ qglobals, ?- O, v$ p* Z' F) g0 x9 m
[$ x) ?, c( D2 T! n, |  V- `' ^; t
  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 b6 T/ X6 N6 E: @4 y
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
: H& j7 w+ |" G, f" g8 q* g4 @  acceleration             ;; the constant that controls how much a car speeds up or slows down by if  z2 J$ n+ V: N6 ]/ j& e
                           ;; it is to accelerate or decelerate
8 T9 ]9 q' ~# w  k& z6 K( Y7 w' S  phase                    ;; keeps track of the phase
. |4 D) O2 x3 [+ @  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure% t# m) g) [; n; f# ?6 t
  current-light            ;; the currently selected light
! l+ Z+ z4 o7 i4 R" k0 R9 x; s( ^0 h3 }2 {% n% H) d) @+ V: [
  ;; patch agentsets; ~0 o. Y/ `' w, ]' @! C
  intersections ;; agentset containing the patches that are intersections
; a1 Q" v9 a& H  roads         ;; agentset containing the patches that are roads
& J9 t1 e  i" ]; W4 A# s7 v]
' p2 t- z: r* L' [* d) I: M
7 C0 a/ S. V2 y+ L. t+ C  J: _turtles-own% N! E* }( B1 Z. s" E0 b" {  B
[. k+ ?" N% C+ f  ~
  speed     ;; the speed of the turtle
& m$ P& T% C* X& `1 G) I  up-car?   ;; true if the turtle moves downwards and false if it moves to the right% Z6 W7 J+ P9 m7 k! E
  wait-time ;; the amount of time since the last time a turtle has moved2 q' u9 b/ ?. J4 t* d0 C) \
]' S; r  D# N5 O8 G) O
* ?# R* E$ m. J' f+ s4 p- _
patches-own5 r" ^0 G7 C; f
[
: _0 t2 Y5 [* Z) U* v* L# ?  m  intersection?   ;; true if the patch is at the intersection of two roads
1 Q2 a. ]! R4 v5 p  green-light-up? ;; true if the green light is above the intersection.  otherwise, false." m- v5 f0 f1 [) r% w
                  ;; false for a non-intersection patches.5 Z0 v7 O5 b6 @* N) S: b2 p
  my-row          ;; the row of the intersection counting from the upper left corner of the1 a* I1 }0 ^! P/ x9 S9 U
                  ;; world.  -1 for non-intersection patches.
4 @  S, U; X; G  a3 \7 D. H  my-column       ;; the column of the intersection counting from the upper left corner of the  {) j* M- h2 h6 F
                  ;; world.  -1 for non-intersection patches.
+ \# l$ d; j( \  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.$ @% {8 L) Y! b6 C' ?
  auto?           ;; whether or not this intersection will switch automatically.0 c( I; j/ j) j, D2 Y
                  ;; false for non-intersection patches.( j# \+ m. j, m2 Y+ d3 |
]4 D1 U# @3 X% F  u8 W
2 `' w& [1 I0 \3 H  ^" G* |- w. [
5 D; Z! N! l0 R8 ]# A- a
;;;;;;;;;;;;;;;;;;;;;;+ i( D) D+ f* V* W; S
;; Setup Procedures ;;
# N; K7 L1 S  L0 G) J8 `: x9 P;;;;;;;;;;;;;;;;;;;;;;
7 D  y& k- r* M1 @9 h' T/ L/ {, K8 K3 {5 B& K
;; Initialize the display by giving the global and patch variables initial values.
- v( A# c& M+ w;; Create num-cars of turtles if there are enough road patches for one turtle to
6 R8 T# G4 w" Y; p;; be created per road patch. Set up the plots.
9 T, }7 ^9 n* f4 V$ mto setup8 [# _* G8 Z! ?* V* Q9 `, _
  ca7 t1 F1 y! J, v: o4 c
  setup-globals
* S* @7 u! k  A# A# d( W9 d
; ~. b- o6 N$ g3 V& R  ;; First we ask the patches to draw themselves and set up a few variables" M4 v6 D$ t2 a- Y
  setup-patches
) s  h3 S, {6 \% b* m1 F6 O6 K  make-current one-of intersections! Y# E- g2 B) I8 {3 Z
  label-current6 a$ r3 s( Z! L5 {8 n* H
- N1 _. v! K& U& A0 D. x
  set-default-shape turtles "car"
6 q' p2 i# o" @. i: n3 Y" I' P+ Y% B6 n
  if (num-cars > count roads)
+ O1 T$ r! G- C0 B0 X, l  [$ [! ]+ b9 g2 x( J2 D
    user-message (word "There are too many cars for the amount of "
2 J7 M0 _5 k, f/ d" M) \* j                       "road.  Either increase the amount of roads "
4 s$ y% I0 k/ Y. ]  P, }0 E7 @                       "by increasing the GRID-SIZE-X or "
; ^9 K/ G& O- |- W/ M, G2 q                       "GRID-SIZE-Y sliders, or decrease the "0 D; @# h% b  n- G& [6 p7 k
                       "number of cars by lowering the NUMBER slider.\n"  d( d, I7 J" H/ D) B
                       "The setup has stopped.")
9 ^9 ]  Y) ?* U% W2 j9 a& E  S# {    stop! V5 j; Y. Z3 ]) y" g* b! N
  ]
- Q+ d& Z; m  Y6 d
. K/ E9 I; B6 @8 D" u  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
: i8 D9 u& H) c1 o9 s  crt num-cars
* V/ B6 m7 B( q; g9 G8 X2 o  [  k' l$ `& t9 k7 I$ j: X6 G1 S7 \
    setup-cars8 `% Z) J. m  e& U8 t4 u/ }3 C
    set-car-color
2 r" j7 n. u, C/ V$ @/ p    record-data
* }5 r( Y% P/ }4 U  ], a: [% R: C" c& ]. D6 d% }

# Q$ P" E: u2 T  ;; give the turtles an initial speed
  |- E- }/ G- k0 V' D  ask turtles [ set-car-speed ]
3 d1 j: n4 D# V8 q+ M8 v" a
% W) U4 u$ e& J! y; R5 r, @: C& x  reset-ticks
& c+ s' f1 [4 i3 w( |1 s* Xend  ]: U2 [* f: |1 {. _

5 |9 y5 Z4 p  S& M3 n7 [. V( t;; Initialize the global variables to appropriate values! U2 R" i$ K: Q' D$ u$ w
to setup-globals
- N4 F, _% g2 H4 o2 \  set current-light nobody ;; just for now, since there are no lights yet
. L( A' N1 |+ o" Q- Y9 A, u, L1 @  set phase 0
' `2 v# [7 L4 M! A; J* d; y  set num-cars-stopped 0
- D" L/ a" d( [3 U$ k: ?  set grid-x-inc world-width / grid-size-x
+ p2 _$ ^$ M! r" Y3 I7 y  s' f3 ~2 x9 e  set grid-y-inc world-height / grid-size-y
; i& H( v4 }5 D' \) j& k' G4 g+ z. D- F9 m! r
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary. Z) Y# ?- |* _- q0 N8 a: V# c
  set acceleration 0.099$ W4 i+ F4 O) P9 z7 Z6 S
end
( c' D* F1 K* r/ r7 e
3 f, X1 S/ _  N  J$ k;; Make the patches have appropriate colors, set up the roads and intersections agentsets,: O# D4 K) e. j  {- I; W! k: ]
;; and initialize the traffic lights to one setting
+ w- D4 @4 B. i% Y" L% i8 v$ yto setup-patches
  w: s% ?' }: q: w$ ?  ;; initialize the patch-owned variables and color the patches to a base-color4 u2 Z7 t3 V2 D  L% N; `
  ask patches
0 S5 ^" N$ I% c% G  [
, O0 [+ Y& b$ T9 }5 Z    set intersection? false) N0 a9 g- H* y* V4 A8 L' s9 K$ Q
    set auto? false
; B( i1 L! B; e% P1 P    set green-light-up? true5 h4 B3 R: M) Y" B, Q
    set my-row -1# Y2 c$ l5 E' t
    set my-column -1
9 \5 \2 N1 u7 u/ d$ g- Z    set my-phase -12 R/ ?/ j6 d, w; f. f7 I
    set pcolor brown + 3' H- q  A) h- A, |$ X- `
  ]
5 ^1 J9 f* m: O5 j& n. }; a% H# h7 l' B1 y# V1 M2 x, W" A
  ;; initialize the global variables that hold patch agentsets
* G0 c  ], i& Z7 f, q2 r4 }% ]  set roads patches with
/ n& o- V( P$ n. L% h    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
) {0 O: X# \# B* G. v0 z: ]    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
, m( ?8 D4 Z" z5 H3 u; e1 ]! v  set intersections roads with
1 C, ]8 J; H* i7 I0 x; Z    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and* V6 p  Q- N& F: a; F4 J+ q4 A
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 j# L  P# z; Y. K7 r; {
( X% W) T" n9 Z  X( D  ask roads [ set pcolor white ]; _0 j7 C* [/ _0 ]+ E
    setup-intersections
9 v9 U+ r2 q- s4 S3 K  rend! Y7 h: Q& ~6 O2 c# W  T
其中定义道路的句子,如下所示,是什么意思啊?, n' S+ i1 z) ]( |! ^9 b9 r
set roads patches with4 k! V; Y( U2 w5 }2 @1 h
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
  R' M! w! }, F3 V% |  U    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
: `( ]: S" U: n9 _8 [; z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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