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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。, ^5 U0 T9 p5 X1 i6 w
netlogo自带的social science--traffic grid这一例子当中,
, V  j9 h) V* b( d6 i7 N4 l7 Jglobals" f( h) m8 r, U' r; e- G" C' n' n. d+ R
[$ x+ v1 ?6 h, ~: \! _2 f3 r1 l
  grid-x-inc               ;; the amount of patches in between two roads in the x direction2 l5 n7 E( ^3 r7 L4 ]1 r) z- x2 u
  grid-y-inc               ;; the amount of patches in between two roads in the y direction, n8 f! n- }$ T# K2 }; U
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if) [: a! v; W2 N6 N
                           ;; it is to accelerate or decelerate% q( `4 h. z& U5 c  l8 ?
  phase                    ;; keeps track of the phase
+ ?# H, A& P5 D4 Q9 O  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure" O0 _- T  U" ^
  current-light            ;; the currently selected light
5 M9 V! M* q/ `2 n
+ s: N" j, l  Y, g* E% h  ;; patch agentsets
5 p( [- A6 P( D* N7 d7 l$ V; V  intersections ;; agentset containing the patches that are intersections4 u# I7 x/ z  _8 Z
  roads         ;; agentset containing the patches that are roads0 e4 X% n4 W$ g
]
$ z8 ~; D2 k; p2 q8 K9 p- t1 r3 ?3 r; [+ }; B
turtles-own
" e3 B, A9 y/ @2 m; m+ V( h[
5 ~4 h! q( {( x9 R- b  speed     ;; the speed of the turtle
/ J0 `( G# @9 C9 q1 O# S0 B/ S7 [  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
1 N" B  ?; W* c' _  K0 w  wait-time ;; the amount of time since the last time a turtle has moved
( ], I9 O$ ~$ \( J7 M# f, q]* u: G; {; t, F' W8 ^( f4 h2 |0 `

/ w( {' v. h! l# _/ P3 f$ Fpatches-own. _. U2 H% Q  m
[
8 B% q$ x+ k: E7 B# {  intersection?   ;; true if the patch is at the intersection of two roads* f% P: _% A5 v) m7 c2 l
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
8 j: `4 T2 s) I2 o- }# w                  ;; false for a non-intersection patches.
! `8 M! N0 S. @  my-row          ;; the row of the intersection counting from the upper left corner of the8 m2 c7 A" ~' K0 p+ v
                  ;; world.  -1 for non-intersection patches.
' b/ H* H  P+ y, w- j  my-column       ;; the column of the intersection counting from the upper left corner of the! N" \+ d7 J5 p. U. i
                  ;; world.  -1 for non-intersection patches.7 t( o5 b  @1 q& n7 U  l# K
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.3 g$ R8 P' S! |1 |4 R4 |
  auto?           ;; whether or not this intersection will switch automatically.
7 S. ]& Y( `/ K* I2 ?                  ;; false for non-intersection patches./ w+ B8 l( e+ @9 ?: n  O% A, K
]
9 V4 j3 m# Y+ o1 _0 o1 Z- b9 K; c" P2 U( J- X
0 V9 h' U  N* J# r5 i
;;;;;;;;;;;;;;;;;;;;;;
, S* `% C8 z4 O' A;; Setup Procedures ;;" ?  ^! T; U% ^
;;;;;;;;;;;;;;;;;;;;;;$ t8 s  ~$ B2 w( U0 m: V* v) ^4 n
  g+ O+ X8 D$ |8 w( N5 \$ {+ \
;; Initialize the display by giving the global and patch variables initial values.
8 N, d" X! M/ P7 f& w;; Create num-cars of turtles if there are enough road patches for one turtle to# U% e* s4 @+ t
;; be created per road patch. Set up the plots.
/ f; y; K! d% U8 m6 e: ]to setup
" J) @" v* T3 ]) r9 o4 T9 v2 z2 e- M  ca
6 t( b/ U# j# t  E) C, H( _) i  setup-globals6 |7 a( B7 e/ `
! b$ q3 J" ^% `
  ;; First we ask the patches to draw themselves and set up a few variables+ g1 y5 U2 S# {- z
  setup-patches7 Z# V. O% a' v( {
  make-current one-of intersections8 a  n, F# [3 G8 O
  label-current
% W  r$ z: j$ q& g
, A. \6 i  T5 s" m  set-default-shape turtles "car"* ]9 j, m" g% s7 ^0 @
! d6 E/ _' x# y6 e) z( V4 _( }: P
  if (num-cars > count roads)
6 R3 O9 t5 W, y8 y  [& M0 }# P7 F/ V% q1 O1 g0 A8 ^  o
    user-message (word "There are too many cars for the amount of "; v0 @8 u: Y2 {& ]/ @% w( t7 v, m
                       "road.  Either increase the amount of roads "0 K1 ?/ I5 H& M) X  k# k
                       "by increasing the GRID-SIZE-X or "4 c4 D1 @# F$ t  M. s! [
                       "GRID-SIZE-Y sliders, or decrease the "
2 j( [5 k7 A+ L1 l1 K! s+ F' k                       "number of cars by lowering the NUMBER slider.\n"( @$ g7 s+ k$ d
                       "The setup has stopped.")( K2 Z8 U3 N0 u
    stop
+ E) P" Y$ S6 J, W1 f) S2 f& ?) h  ]
# D: t0 ^2 A' Z4 }2 n* i3 v+ t. r" n
- B" G2 b% |* }3 v; ^2 k% y  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color8 z; l' V" o7 l/ x
  crt num-cars1 W# n+ O& x  h/ i0 X$ i; D. d. p
  [
3 F% P7 r* x$ j( ^; B  m6 D    setup-cars
+ a, c! b6 y# M/ s8 l    set-car-color( f) ^- r, ~, N, G& _1 S
    record-data! n! N1 y2 b6 U& e: M) _7 q
  ]6 N5 E  e  ~" m' a: W
& x7 e$ u* W$ |0 [4 f+ i, t
  ;; give the turtles an initial speed- W  O: Q0 H7 ^5 d: F% T! h  [  d. c
  ask turtles [ set-car-speed ]/ m: @+ M$ Y+ E* V
) g9 z4 n1 j* G3 m
  reset-ticks. o( u8 Q& u1 {% Y6 Y7 j2 ^
end
, {6 d# C4 W$ Z' e* D* v2 A5 e2 o/ H  b
;; Initialize the global variables to appropriate values
" q- r, _- @! `; Sto setup-globals- u; f" r! w+ K, y, m: |
  set current-light nobody ;; just for now, since there are no lights yet
8 E5 ]5 x, X8 @: W' L" S  set phase 0
, s2 i4 r  d0 f  set num-cars-stopped 0
) T9 S  l" k0 @0 A6 {9 Y- g9 H0 W  set grid-x-inc world-width / grid-size-x
# y% L1 m' w+ b  ^  set grid-y-inc world-height / grid-size-y
* [, X6 p" I7 _6 z# y2 V# `4 W0 H( V  a8 X; o( L
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary. a) C; D! O$ a4 v( ^" R3 B- L' J/ _
  set acceleration 0.099
4 L. s4 T; W; o, v$ y+ R: w. Bend
- ~( Z: u% K: k7 q1 `  D: F- w7 P) M- L: V0 D/ i4 H
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
! k) N# Q! C: J8 F- d;; and initialize the traffic lights to one setting
; }1 U% o7 J# Y$ s2 }5 Y4 y( |to setup-patches+ X0 K8 ]: f: j9 J3 B+ a
  ;; initialize the patch-owned variables and color the patches to a base-color
& O& ]& g9 N& z0 q! w7 x  ask patches" [" w* U! W( i6 v9 h4 ], x$ o( X
  [2 j# u0 s) f1 \' m
    set intersection? false
: z% p' V# M. h1 ~. m, N; ~    set auto? false! e' o- H2 `4 d9 c
    set green-light-up? true
$ L$ S6 K! ^7 ?    set my-row -1
0 L1 D+ q- }- U# X, G9 M2 G    set my-column -1* g6 y6 T0 a; ^5 ?& ?0 ~) K+ h
    set my-phase -1' o0 J! M8 F5 a; Q" V& d! L
    set pcolor brown + 3
) x# ~' Y! v+ v5 P& W) j/ v  ]  |3 U7 ~6 x5 B* V9 q( z& p- u& B
% o- o/ j% w, m5 E
  ;; initialize the global variables that hold patch agentsets
! I# A) T# g: `- l  set roads patches with. [# y& S) R: U* p5 n5 V  f% Z
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
* r! M* J* k: k  z# A, Y) B4 B    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
$ m' D8 Q7 ?$ A  set intersections roads with5 X0 P' W: S, P: _) b4 N) z  I) i+ I
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and! b/ e- u' C: ^0 x- a$ Y8 d4 j6 m
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
5 d( U- ^8 D& x- t% j3 [$ c) `
* E+ l4 L  E+ r4 E& t3 R! B  ask roads [ set pcolor white ]/ n2 {  b& e) K
    setup-intersections
: P; @- D; t* l' X2 Y/ _# F- ^; oend% Z1 z/ ^. C/ J0 b! l
其中定义道路的句子,如下所示,是什么意思啊?
: s4 c+ l% |/ m$ ^/ C% R set roads patches with! x" @! c- o2 Z; g3 ]' |
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or7 \& _5 {3 d  b+ I
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
" t  j! ]( ?: h, e# K% s) s+ q1 ^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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