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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。( {" [$ j( _& F
netlogo自带的social science--traffic grid这一例子当中,
1 C  m9 l9 \% Z- W! c) A; h* }" lglobals
2 s& l$ d% c) q! T9 {2 f* a[6 d$ ^+ a& }2 X( t% Z8 S
  grid-x-inc               ;; the amount of patches in between two roads in the x direction& A5 V$ V- K7 y( s: J8 _
  grid-y-inc               ;; the amount of patches in between two roads in the y direction' `1 U  y7 z0 Q  {+ u! F1 c3 l7 h
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
1 b& X3 ^$ Y1 q: G2 i                           ;; it is to accelerate or decelerate, F9 h* ?8 h& C& y( P9 y
  phase                    ;; keeps track of the phase
6 S  ~# W( V0 [) G7 u  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
+ @6 f- i. n8 j, O* s' p# E  current-light            ;; the currently selected light
# w1 l% }4 M( k3 c: Y% o
' ^* M  h, D+ g8 Z% ^0 w2 @  ;; patch agentsets# ?: d, K% W! ~+ I' ]
  intersections ;; agentset containing the patches that are intersections
/ K4 {  o# e4 M. f0 ^7 q, u  roads         ;; agentset containing the patches that are roads
, A4 u5 ^6 P9 \# s, l5 _, `]# Z. ~" @: e) L; @( z+ v
( |$ \  p  o$ w4 g1 O
turtles-own' c6 c+ s) e/ L. n+ G& z
[
- t8 J1 J0 n6 p3 P& L2 }  speed     ;; the speed of the turtle, g& B& A9 ?; T- @7 ]: c2 F
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
1 ^# x6 X1 N9 M$ S  wait-time ;; the amount of time since the last time a turtle has moved
6 I# d$ l+ `8 w/ I]
- \5 x' x8 U! a9 l9 l+ `2 A, a: ~! P) Z  A
patches-own! i3 h) S# N* O
[
$ w- |; t1 n  b9 U! @3 e. [  intersection?   ;; true if the patch is at the intersection of two roads
; m& P+ `. p1 v( O  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.- z; r4 K; S) S2 J8 s
                  ;; false for a non-intersection patches.% z, O! ^; y' ~7 w  [* ]! C# [( V
  my-row          ;; the row of the intersection counting from the upper left corner of the
: X4 N0 W. C6 C6 V6 g3 @1 F, o                  ;; world.  -1 for non-intersection patches.
  G  P$ {: ^! a( `  k7 _  my-column       ;; the column of the intersection counting from the upper left corner of the
# t/ ?- a. d. {0 l% [& q0 t, F                  ;; world.  -1 for non-intersection patches.5 }( ~# F( h' r% Y9 z" G
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.. t! F- t- ]2 S8 X# m; \% P
  auto?           ;; whether or not this intersection will switch automatically.
+ |$ A6 X; I4 r( i                  ;; false for non-intersection patches.! r2 D  ^$ P3 F/ \, g
]3 f- v: K6 }7 X' Z. x& I

$ C5 W7 O8 O' l, B0 L9 v: T: `; D- |. b; `3 K2 }' u
;;;;;;;;;;;;;;;;;;;;;;6 d3 i& e9 u, @" n) s; {
;; Setup Procedures ;;. a2 R+ v: C# D) N. n# g# Z' @
;;;;;;;;;;;;;;;;;;;;;;
' F, \! Z5 k# a" _7 o) R. k; V% |) d: d- i/ m& w0 e. w* a
;; Initialize the display by giving the global and patch variables initial values.
7 [5 K- \  j+ X3 e8 _/ O9 _# X( p;; Create num-cars of turtles if there are enough road patches for one turtle to
6 v3 v2 ~3 z4 j" t/ N;; be created per road patch. Set up the plots.! n) g8 V: N1 [. F
to setup4 ^* f/ s6 Y' l0 w, [+ X. B
  ca  |( m$ {6 L. v2 @
  setup-globals
' ?' Q1 A5 M7 x; B, H1 I
# a& P" s. Y! y2 g& i$ |/ l  ;; First we ask the patches to draw themselves and set up a few variables$ }2 g; ^' L2 [+ H% g4 k
  setup-patches
) D; Z  X% G1 D2 W9 u  make-current one-of intersections' i) L. z% v" e3 T
  label-current
/ `3 j: ~) |3 ~; t8 F/ n# @. N, o4 ~' ^, c$ p- r# M: v# G' \
  set-default-shape turtles "car"/ l" Q* V7 c: B, l

* \% B  R) K+ ?( w  if (num-cars > count roads)
- l+ d  Y3 p2 q7 M! e  [1 ~6 @4 J. r0 |- g5 o
    user-message (word "There are too many cars for the amount of "7 F& e8 [  W4 a( l* [5 v8 B8 |0 v0 n% x
                       "road.  Either increase the amount of roads "" t7 ^, N5 D7 T0 {0 S
                       "by increasing the GRID-SIZE-X or "
8 d4 v5 A& p1 m) T                       "GRID-SIZE-Y sliders, or decrease the "
& `3 j, L: L$ Z# Q! `                       "number of cars by lowering the NUMBER slider.\n"
4 S+ `7 ~2 g  @9 Q6 c# f                       "The setup has stopped.")% D- X7 ]( C& C2 ?
    stop
+ i, W! F1 C5 E8 F; S' x' ^6 I  ]9 E! k" U8 _9 t( y. ?+ W" G
- E5 o. t6 D& b: }7 b
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
' {: a2 j3 k$ @  E& Y% v9 V  crt num-cars
# I/ g4 m( f  r$ v  [
' C$ W% _3 n+ T; J. z' C    setup-cars  J3 g  W+ C$ [7 P+ M) f  Z
    set-car-color. e( W* F9 v- X" {0 T# F- W
    record-data
' k2 X; Q& f( h, m6 u% |" T0 t  ]- o" J) k* D1 r: Q# [1 `  e7 G& [

6 m2 \2 `: `2 g5 E& u  ;; give the turtles an initial speed' s3 S' a! a# m+ ]+ R" Q
  ask turtles [ set-car-speed ]3 E, Q9 L( ~6 g0 h4 M

( r, l+ X0 g2 O  reset-ticks' C" z/ W+ D2 q2 u' z
end
* b3 L. i5 h$ T& k" `; L0 d# |( ?7 u1 }
;; Initialize the global variables to appropriate values. Y. P, r2 F3 c6 ]
to setup-globals" Z/ V5 O: l: W6 @$ g; Z
  set current-light nobody ;; just for now, since there are no lights yet
3 v9 e; M2 [0 A  set phase 0
( N$ h2 c7 s3 ?0 h- k; o6 I  set num-cars-stopped 0: T. ^0 X7 k1 N  Y  F! J. j/ a' U' L
  set grid-x-inc world-width / grid-size-x8 E0 Q& M  {+ W, m$ i4 g$ B
  set grid-y-inc world-height / grid-size-y2 w4 |2 {. T& \. j8 h1 C
; M! C( s5 q7 j8 \2 D
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
! {( r5 H" G4 l/ C$ b. q5 ~  set acceleration 0.099
7 f% e6 G% s# R5 u7 E6 ?* q4 mend
& f* c: E7 c+ x1 m" G4 h) V
8 B3 B, ~. M# z4 F- D. Z/ `# ]# a;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
0 }* H: w# L$ l9 ]" ]5 Z2 b" C, o;; and initialize the traffic lights to one setting
3 s0 r8 J1 N# Z0 _to setup-patches' }3 M( v8 y6 w' l3 y
  ;; initialize the patch-owned variables and color the patches to a base-color
  q$ x1 o; v- P, v* U  G  ask patches
/ A" P1 F5 F1 n2 g4 ]  [
- F! |2 w# V4 k  S    set intersection? false
. t  w4 _9 A; }6 H    set auto? false% b8 y% e5 x$ H) s; T
    set green-light-up? true3 b, W: V5 X8 R
    set my-row -1
+ P. U1 u6 b) {! n    set my-column -1
/ {4 Q* K6 m. z' j( P) f) i    set my-phase -17 |# I" i; Q0 ?3 g8 Q2 b% q( Z( f- |
    set pcolor brown + 39 ?7 V! {+ A0 o- m1 d8 L& F+ Z& [
  ]
. m8 C9 s" D9 s9 |! u1 r4 D( u1 g' O" m" k5 m+ `% l
  ;; initialize the global variables that hold patch agentsets
6 H* F7 s" c8 J, b& J+ W! b  set roads patches with9 t7 I4 J. b3 {
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or$ f5 x( Q4 l7 L/ f+ u
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 d2 r7 W0 {) l  set intersections roads with
. J3 L! p0 l% Y    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and% q) J& I9 j- @
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
# w- r( D& V0 l& T, f! y# }6 c7 T2 U& `' c
  ask roads [ set pcolor white ]0 S, g1 }3 e  u- p4 R% F
    setup-intersections* w  r! s! \' P; l. N
end: T2 }# s/ }, [4 k9 t5 V* o
其中定义道路的句子,如下所示,是什么意思啊?
- A6 ]$ Y1 P; M* w set roads patches with& ~. [6 x( T, K$ Z4 K8 T2 N
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or# i) @8 w4 ]( |# Y3 T) S
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) s  X+ P1 N* [0 P6 n2 L
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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