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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。
1 U3 V, o3 l% p  z: E- f; znetlogo自带的social science--traffic grid这一例子当中,- H$ L0 F7 {; o( p$ ?
globals
* @/ r$ F4 C+ r9 z. x0 [0 f6 Q[& Y& t  j8 U, v3 y
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
- T. d& j0 ?  r. ~1 m; N  grid-y-inc               ;; the amount of patches in between two roads in the y direction
2 i& t: m4 U6 I+ I# y6 x4 H  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
* h/ h. K  c$ S/ \                           ;; it is to accelerate or decelerate
% p4 s# n. W$ k3 E: z- k5 R  phase                    ;; keeps track of the phase
( A2 P& I+ d, K" b& E  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure& [, _$ U9 x  o1 Y
  current-light            ;; the currently selected light1 e, P; U( N, `: w# Q! F
4 W0 N, f6 s- {5 v, R6 j# c1 V
  ;; patch agentsets
3 a( g0 D& j( _1 v  intersections ;; agentset containing the patches that are intersections/ I9 {8 ~9 s4 [
  roads         ;; agentset containing the patches that are roads; E2 ^$ H; S/ \
]4 j: K/ W1 f& y* M1 ?

+ N- c/ ?1 P: N8 q- S9 p/ S2 _& Iturtles-own
0 B& r1 l, I# F[- l- [+ f1 Z* S- ]4 R) ?3 h
  speed     ;; the speed of the turtle
3 z. r+ K" w# H, B  up-car?   ;; true if the turtle moves downwards and false if it moves to the right1 b6 k" e; K3 M# y* ~2 R
  wait-time ;; the amount of time since the last time a turtle has moved
3 F2 e8 k) Z1 R" q/ b/ T2 D! m# p]/ l2 Q$ ~0 ^3 m( H
. \+ ]4 m# [' Z: f5 u6 `
patches-own/ F( F5 I8 |/ s& @6 b
[
* P& f  f( m% p" t6 [  intersection?   ;; true if the patch is at the intersection of two roads+ X: [+ U8 x& n( x$ D
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
* J0 u; }! j) f; [                  ;; false for a non-intersection patches.9 t# U" a& J; k8 T& W0 B1 ^
  my-row          ;; the row of the intersection counting from the upper left corner of the& D2 a  h9 B* r* b/ R6 ^. M
                  ;; world.  -1 for non-intersection patches.
0 S' l1 i* f( r$ Y) t! B  my-column       ;; the column of the intersection counting from the upper left corner of the' v, ]" s4 M; p
                  ;; world.  -1 for non-intersection patches.
( C' z2 k$ W9 }  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.$ o- q+ w* U  g) G
  auto?           ;; whether or not this intersection will switch automatically.
# w6 h! N( ?, `                  ;; false for non-intersection patches.2 X' v0 U) E) u
]
" V. D& u- n6 p. V  T9 j' v, }; b8 i3 r1 ?: m2 T' D( u& m9 h

. n7 k1 {: v$ |% O+ };;;;;;;;;;;;;;;;;;;;;;$ N1 W% P( C1 [0 t
;; Setup Procedures ;;% i; U. x% Q- \
;;;;;;;;;;;;;;;;;;;;;;& ?+ E; `  L9 d& B, L8 y
) e! V* H- I1 M
;; Initialize the display by giving the global and patch variables initial values.( U# ?. D( ^5 y# T$ ^
;; Create num-cars of turtles if there are enough road patches for one turtle to
3 M- g* E+ |0 b  o( t7 G( B& n( a;; be created per road patch. Set up the plots.
, R, _! I5 I5 L9 Wto setup
# m( q  Z  n5 F8 \: G  ca
4 Q6 p1 ~; H3 F) I) j$ s/ c" [  setup-globals
: I, e" [, F$ j/ R; q; v7 b% c  h) K  U! a! r' X! J+ j6 }! n
  ;; First we ask the patches to draw themselves and set up a few variables
- ?2 o% l9 U0 p: r/ _8 K  setup-patches
4 Q8 j/ ~! A% f8 |/ x! |  make-current one-of intersections
, m( i/ [; b3 o  a& v' `0 U. u! R  label-current
. G, R+ O1 D+ z7 H0 G2 M' a
5 _( L: J; j& d# K  set-default-shape turtles "car", V" N( D5 x" A4 u) h$ Q* @" J3 ^1 F
4 S* X6 O; c9 d) X( A
  if (num-cars > count roads)
, c+ q* T- C/ N  [
% @. ?- l8 `3 ~3 p( g    user-message (word "There are too many cars for the amount of "0 R. `% K& k& l. i
                       "road.  Either increase the amount of roads ": @9 a6 N: ?; R' f, Q0 i9 o
                       "by increasing the GRID-SIZE-X or "6 h5 U' P* v1 b/ |; h
                       "GRID-SIZE-Y sliders, or decrease the "
$ u2 ]# D, b' ?7 ?4 D. }                       "number of cars by lowering the NUMBER slider.\n"6 @) W3 t6 F, L! |/ p
                       "The setup has stopped.")
" k4 l; k4 R; H( _/ E' _5 \$ I    stop1 ]. v7 F4 a& J: S9 L
  ]$ j( F% b+ ^& K. m$ d0 l  v
& D9 u: n- |! [% O8 I; J0 Y
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
+ N+ d; L- w9 A- ^- Y/ @. E  crt num-cars
5 o" L; E( C5 ~& @; X8 a: K8 J, I# W  [
6 N0 Y7 D) D, G) f: c3 n* _0 N/ b    setup-cars
4 |+ a) T. w. N: K. U    set-car-color
' G3 U2 ^0 v3 e  Y) t4 K3 t$ ^    record-data
% L& n: ]& Q9 w3 ]0 P* D! ]  ]4 b0 {3 A  q# \* Q+ h# k
' |% N% f+ f% L7 t+ ]& Y
  ;; give the turtles an initial speed
/ r- c7 G* I+ [  `  L  ask turtles [ set-car-speed ]; n& j/ n, T8 J1 O
# A1 Q- k1 B/ X5 }# v& M$ c
  reset-ticks/ ~/ U/ Q$ N  S7 _. e
end
* |6 x" b% m+ c6 e2 Q- E" d& ]1 o/ c/ Q# N
;; Initialize the global variables to appropriate values: f& W7 W7 a- Q0 E3 q
to setup-globals1 y/ a0 F& |) d- _$ ^$ D- E) k
  set current-light nobody ;; just for now, since there are no lights yet" h: I3 F% U  }- ~
  set phase 0, [$ z0 i. M/ q! z  ]
  set num-cars-stopped 0
6 m1 v! F0 a# t$ [: c, B3 A) }  set grid-x-inc world-width / grid-size-x# s  E. X" H( h+ p2 K
  set grid-y-inc world-height / grid-size-y
$ S0 O/ I/ U5 ?# C
' N" ?. u) e2 J$ _- j/ q5 F+ v4 J  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary# o6 p. r& ~' E/ [# l
  set acceleration 0.099
8 k- _$ j5 J7 Eend0 C# G* q. j+ P0 M6 \+ n
. {0 a0 V; q' d# m" Z0 f# @
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
( M) x7 C) R: g* R$ ~;; and initialize the traffic lights to one setting9 o) t7 q% \4 }, f2 H5 K9 p
to setup-patches* T& C6 M# [5 k* K" _# e* L+ }
  ;; initialize the patch-owned variables and color the patches to a base-color: M4 }" X) P9 S" Q! X
  ask patches4 l6 @' O% L2 K# _. u4 N% H
  [
: {) Y5 f: V* V9 u/ d4 b    set intersection? false% {0 k6 r' Q- d( ]% f
    set auto? false5 x* E* i6 b6 ^, N6 C4 Z5 C0 N
    set green-light-up? true
4 u5 z3 u( X# V/ u  P* F0 t0 D    set my-row -1
7 N& e! l* l: y! W: Q, k    set my-column -1
$ \( ~& u. \7 t; A, [  m    set my-phase -18 N& q& D, h: T/ y* D0 O
    set pcolor brown + 3
8 c5 h9 f) X; e; Z/ d! F& h  ]/ }9 d6 V: e4 J7 g
) k; v. @+ U7 i0 ~* i
  ;; initialize the global variables that hold patch agentsets
3 ]; @: p) I+ Q  I- u% |  set roads patches with( r7 t  C& i& W+ J
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or" _6 k' |  s; T1 N" z2 k1 L" t
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]3 y$ [9 ?  Y: a0 q
  set intersections roads with/ p$ q) o* n/ }4 H/ G) g( D- x
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and" n+ M$ ?! f# Y1 F: N
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
& t$ x( ~; z0 ^# A/ }9 q5 L# G* _: l& ]  H' f
  ask roads [ set pcolor white ]! e3 e5 k  `2 A) W7 H
    setup-intersections# _" G) w+ ^3 S1 E. ?5 c( ~. L
end
9 K/ |8 `* t, f# A其中定义道路的句子,如下所示,是什么意思啊?
% H2 M: B3 e. M$ }4 `& C set roads patches with
8 l2 O8 }# }6 E+ X* H6 _- G; ?    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
8 V: p/ @+ v9 s9 L; n  b- A    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
& [, o: U* k8 v9 Q" m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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