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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。8 V8 S/ z1 W) Z0 R
netlogo自带的social science--traffic grid这一例子当中,
$ N3 x2 m: [2 Yglobals
1 a6 C$ {, |( }( s, L" B5 n[
2 s% ]9 F/ c. g8 ]' K/ n  grid-x-inc               ;; the amount of patches in between two roads in the x direction  ]/ w# E& ~4 G0 F! e2 ]% }) ~
  grid-y-inc               ;; the amount of patches in between two roads in the y direction# F) E. Z% A. h) q! n
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if4 X1 d3 [7 Q* c( E/ ], p- x  z3 P
                           ;; it is to accelerate or decelerate' f. x' M) ^& R( @
  phase                    ;; keeps track of the phase5 }' }# P* Z% A! d3 O. `! o2 t
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure/ v6 ^$ U3 u3 ^+ d2 E  i- m' E1 @7 z
  current-light            ;; the currently selected light9 s" b" e0 B9 o* a8 ]
& V; V3 b& n  _$ l
  ;; patch agentsets; a. R" O' c, M: O& o2 o
  intersections ;; agentset containing the patches that are intersections
1 p& V8 U& V4 Q; C6 l: l! `  roads         ;; agentset containing the patches that are roads6 l6 R* k& w- I* W) I1 a
]! V( y4 E" J, a5 `- |, S$ w
# e; T9 A# n+ I, f
turtles-own  X5 O/ o. Q9 X( F
[
+ s6 q# T( }! ]( v  speed     ;; the speed of the turtle
1 Y* V8 x4 O7 A3 x) R. @" j# f+ K  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
  ~3 R6 `4 a  S) ~: G5 H  wait-time ;; the amount of time since the last time a turtle has moved
, z' M& W$ Q6 `3 {5 i3 n0 L]
! U& O3 e- g/ s9 B& n
9 j; a6 U( S# {# r+ kpatches-own( I& U: ~4 y; @
[
! Q! ?; z. V+ f" M4 _  intersection?   ;; true if the patch is at the intersection of two roads
. a+ B0 I1 n- l$ D  green-light-up? ;; true if the green light is above the intersection.  otherwise, false., e8 G$ U' L. W2 T$ i
                  ;; false for a non-intersection patches.
' Q$ f: b5 {7 p% }8 N  my-row          ;; the row of the intersection counting from the upper left corner of the
; U1 D( t& {2 t2 s6 _( f! g                  ;; world.  -1 for non-intersection patches.' ?+ @( N# ?8 c7 i3 w& @* }7 R, h
  my-column       ;; the column of the intersection counting from the upper left corner of the
6 H7 s1 @" z7 f  _' w, s3 D: G" ]$ U5 D8 C                  ;; world.  -1 for non-intersection patches.8 ?# w% O$ Y9 X9 D# x8 l* l: ^
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
- o* k: H0 z6 A8 O  auto?           ;; whether or not this intersection will switch automatically.6 C! i; c- p; {, a+ _
                  ;; false for non-intersection patches.! G- E# i+ B, ^- K
]
* p" g7 O' R% v$ M5 S( c  X* ]+ [* X
. j+ G( j) F+ l0 I2 _& ]! }+ @; B6 w: H4 j
;;;;;;;;;;;;;;;;;;;;;;- e& a9 B+ g$ w" ^
;; Setup Procedures ;;+ j. j" G1 ]' P/ v( s, r
;;;;;;;;;;;;;;;;;;;;;;
# s! S7 v2 w  m# `3 ?3 t" p( T& v
/ `1 X3 c/ L6 I& _;; Initialize the display by giving the global and patch variables initial values.8 b, ^, w" X6 q* e2 I
;; Create num-cars of turtles if there are enough road patches for one turtle to
0 y$ D+ \$ D8 x/ D9 I;; be created per road patch. Set up the plots., b; }4 i: e' f% ?
to setup" p" t% k! b, k+ P3 J9 e' [- q  ]
  ca
3 a  `2 E6 g! n  setup-globals
. a5 U! T3 y1 m9 q) {  T
& A6 P0 _2 Q* [1 q3 @! N  ;; First we ask the patches to draw themselves and set up a few variables
/ v$ }1 }) p2 Z1 ~  setup-patches, @7 G4 w  I6 m% ~6 r
  make-current one-of intersections3 P; [: T! D7 Q
  label-current) H  P+ Y" |- F: C; I3 ^; n  R
% O9 O3 ]0 }3 T! k+ {& d
  set-default-shape turtles "car"
8 p% a) \$ }2 p% \; V8 j5 ~  B7 V4 f% K8 G9 l' H
  if (num-cars > count roads)
! G9 L! W$ V" S! X5 e3 T7 q; ?8 f  [
5 ~: A' d$ f1 r& v0 [    user-message (word "There are too many cars for the amount of "
% q4 Q$ ^) y1 _  ]7 s                       "road.  Either increase the amount of roads "0 ]$ k  z! c) ?. ^: t5 y0 @
                       "by increasing the GRID-SIZE-X or "+ F. o9 R. Z: d" p1 U9 f2 m
                       "GRID-SIZE-Y sliders, or decrease the "! l. W0 ^) z# O1 K& a' z: U; D
                       "number of cars by lowering the NUMBER slider.\n"& @- V1 h* P' P1 B) ~9 _
                       "The setup has stopped.")$ U  l  L6 I+ @# W3 g9 l
    stop  I, M) M1 \  a! q, C! c
  ]
; D3 {4 A+ \. _+ n4 D8 ^4 F
# D1 D% k0 d/ {8 \, \) c$ l  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color! U- t6 M- N+ e* J/ Y+ b2 \
  crt num-cars
# C3 B2 O( R) t! I9 n  \) d7 Y  [; u, w  o8 d# Z, }3 L8 H9 \+ b" D
    setup-cars2 m8 F) L3 x& ]0 E5 e4 q8 O
    set-car-color- l; j) m, p0 |+ J: G
    record-data
4 S% K/ `- G1 {8 c$ v3 e" N  ]
* R% r8 L  \% F1 @* \7 _  [; y( q
  ;; give the turtles an initial speed
8 K' |( R& u+ N7 y/ I6 v  ask turtles [ set-car-speed ]
% K9 {3 l' r) E2 c0 k+ c% N/ n0 m4 E* x7 y* ]4 v4 _: {: e* o7 O& I0 c
  reset-ticks
1 V( z. [1 a. L1 m0 fend6 a2 G) q- Q3 @4 ]: p! L
0 p+ z; U2 o# t1 B
;; Initialize the global variables to appropriate values
& T. E. b2 Z1 c5 b' zto setup-globals
, E" o) y9 F% F& u9 x. B  set current-light nobody ;; just for now, since there are no lights yet
4 a5 R9 i0 g% j+ O4 ]7 H  C- C  set phase 0
) s  e9 i+ {. @+ [& P  set num-cars-stopped 0
* n7 U8 V7 q/ V: G  set grid-x-inc world-width / grid-size-x7 _; k2 X, {/ J7 \5 v) E1 e
  set grid-y-inc world-height / grid-size-y. \( p! n3 v9 t: I4 a9 e% L! U) \
; M+ V* R. e* W: N/ Y* e0 Q: h* p" v- J
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary5 G. \. w% D/ @7 G, H
  set acceleration 0.0991 M) I  V1 U0 `8 |& `! o2 h
end
4 u$ Q" v. L% V+ w9 l' S( l1 \' X) ?# r6 o1 z
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
% P+ {1 W4 O: B;; and initialize the traffic lights to one setting
' U* g: d8 F" Q4 d; R5 J1 ato setup-patches
7 @- ]4 ]* C. U6 V4 f  ;; initialize the patch-owned variables and color the patches to a base-color, r+ ~& R& w- c+ b
  ask patches3 k/ S2 u; D/ t7 `/ u& f/ S  r
  [5 d: E+ D4 @, [8 d% m+ ]6 U
    set intersection? false
. x7 V$ n$ X1 k- P/ O$ V    set auto? false9 f- h' Z& b* y# D
    set green-light-up? true' O4 R( E& n3 S% A" x& B$ w
    set my-row -1
  R7 a8 x5 J: Q4 [1 F    set my-column -1
0 V: ^$ \; s3 N6 x# K+ Q* R7 P1 H! U    set my-phase -1
/ W1 ~, p$ [0 [! S5 E    set pcolor brown + 3, ]/ a% p/ G4 a6 N/ q) C  b+ }
  ]: ~. h6 q0 ~9 _- L0 z' u. |7 y+ @

2 b, z( A0 |% |& |  ;; initialize the global variables that hold patch agentsets
  X( G; r+ S0 f' p% T  set roads patches with4 v9 O, {: F4 y! b
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or1 O" f/ j# {" O7 z: j1 q
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]9 _" T. C: p. w9 o
  set intersections roads with
! g1 ]- d' G% Q; B0 M- P5 P    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and9 ^2 h3 ^# u& B
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
+ T9 C$ I0 P! F3 c" u
$ `/ Z! t" m, m, B1 C  ask roads [ set pcolor white ]% R: y% k& D2 _' v
    setup-intersections
& |! R6 s; X& ^$ xend, w8 ^, ^: ], p2 f" @
其中定义道路的句子,如下所示,是什么意思啊?
/ A" n; w- W3 x/ S set roads patches with
) z+ ^" V% x( K" ]( w* ]% l    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
1 n8 E2 ^! H$ E+ W3 s. y3 t    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
5 b( P! U+ T# J- g5 A1 s2 `- h/ 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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