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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。
  B2 X- R. b: c' N: ?* {netlogo自带的social science--traffic grid这一例子当中,' c8 s2 g2 |8 F$ o1 K5 `5 B
globals+ ~( S, u) m4 l" k$ h
[
+ e, a2 H5 L2 D  grid-x-inc               ;; the amount of patches in between two roads in the x direction
7 H- S+ ?$ x6 K2 U1 l  grid-y-inc               ;; the amount of patches in between two roads in the y direction% J1 n8 V; U' V
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if* a! q' W: S) C/ u
                           ;; it is to accelerate or decelerate0 F: [8 n$ u7 n# l3 U) t
  phase                    ;; keeps track of the phase. g% {: N2 k: w$ T. D
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
6 f! f0 E7 p+ V# |  current-light            ;; the currently selected light
: Y! I9 S& G7 X8 M
# w/ g6 L0 i8 R0 j! C  t0 O. i  ;; patch agentsets" e0 Z, j- |  }( W: U. u3 B/ R
  intersections ;; agentset containing the patches that are intersections: h" n& g0 l$ D: ~8 o
  roads         ;; agentset containing the patches that are roads( l- p: A7 ?; K' J1 p4 U8 Q8 J2 @
]6 Z6 F0 V4 k8 s1 u# c

: g" r( R) b7 }  H& _2 aturtles-own% x* W5 K* t1 `' P: K, M+ J, O
[& ]3 z6 F2 l6 @3 x1 ]8 M
  speed     ;; the speed of the turtle
$ b" m! c: {( t  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
* Z) B) f( Y( r$ t5 p8 R  wait-time ;; the amount of time since the last time a turtle has moved
" ~- ]: v' u+ w, M5 u1 i: F% h/ []2 {( H& W9 l9 N) ]; m6 q3 G

" o" ]/ K$ E- [& v0 z: L4 i8 Y  b, V$ Spatches-own
4 ?& G7 A. i- u% i! K2 S4 Y* ?[
4 p8 S  g3 [8 k  intersection?   ;; true if the patch is at the intersection of two roads9 S4 s: x+ m. ^' j. P, G
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
! J! ^# k) R5 e* i& k5 w- {                  ;; false for a non-intersection patches.
" A5 A. {  H3 N& Q# a  X  my-row          ;; the row of the intersection counting from the upper left corner of the: i7 Q: N' k, ~& r
                  ;; world.  -1 for non-intersection patches.
3 `7 P3 U7 E. ~  my-column       ;; the column of the intersection counting from the upper left corner of the( ?* \# q. f+ o
                  ;; world.  -1 for non-intersection patches.
, p1 b$ I1 d( U( ?  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.1 [& h6 Z1 O: n2 u
  auto?           ;; whether or not this intersection will switch automatically.
. ^( n) s- j- P5 C1 s" `* C                  ;; false for non-intersection patches.
, w+ ~& |4 R' l& }+ I: @' [4 \]0 ^& g: T* Q3 ?% ]5 `: x, }

" i  i. ^0 V0 l5 _& r6 e. K& U) g; ?" N7 n/ p
;;;;;;;;;;;;;;;;;;;;;;. h4 }: f# W% x' |6 u1 v
;; Setup Procedures ;;
  X* j3 O* T; N2 {;;;;;;;;;;;;;;;;;;;;;;/ x, [' d0 t9 D, H* s+ {7 k" J/ s

% @6 H! Z, }6 n+ h9 d( ~1 b;; Initialize the display by giving the global and patch variables initial values.6 Z0 Q+ ?8 W' _2 R5 V$ |
;; Create num-cars of turtles if there are enough road patches for one turtle to
9 X9 `3 j  T# g. H3 f% U;; be created per road patch. Set up the plots.
  F$ G$ a5 M* i' N2 p2 n! tto setup
, g9 e2 T# w( S  ca
2 U' s  Y+ a# `. J  setup-globals
3 k* h5 k: m( C8 r& H- \* E6 P% k. V3 A. o3 J8 u8 k/ a
  ;; First we ask the patches to draw themselves and set up a few variables1 G# U6 ^& m6 l2 B% _
  setup-patches. M5 v2 g5 @* ]4 \
  make-current one-of intersections# }$ o) }2 Q) C; y
  label-current: f* `& d3 P! ^
7 ~( U. A+ Z( [/ h
  set-default-shape turtles "car"" b; l" R' S5 f/ `
9 }* b- T, O; M! c
  if (num-cars > count roads)
& t+ R0 q$ E! k% z( A. ?  [
7 }6 u' p4 @( E$ C    user-message (word "There are too many cars for the amount of "! k+ |( z; T# _# G# o5 j1 @% H: V
                       "road.  Either increase the amount of roads "+ n% L9 [( i( ]4 g& i
                       "by increasing the GRID-SIZE-X or "1 M( g5 j' ^# ?# l6 N
                       "GRID-SIZE-Y sliders, or decrease the "; O3 P5 Z7 d  I, v7 }6 ?& V
                       "number of cars by lowering the NUMBER slider.\n"
  d0 m8 X  j2 l                       "The setup has stopped.")+ R* t* L+ }$ }, X& l
    stop7 {8 V/ K- {8 v9 j6 I
  ]
6 I( A" x* o( y  U; F. J) T! @$ e: Y# k5 l
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
! Y& H7 _$ Q( f* _7 i  crt num-cars/ Q; ^) l: }$ ^- t( A
  [
5 Q; q5 g! |  ~# }    setup-cars& d# h/ i' q2 H; A( q, V4 Y
    set-car-color+ r3 S7 C% n2 J6 D1 I# K4 e" N* h
    record-data
1 T9 Y) g' O6 h# @1 }  ]) z& Z! _5 v% X' ~2 _* ]: B

( y3 F' q3 O. G5 n5 r( v8 V$ s  ;; give the turtles an initial speed
4 Q* o" @# l2 Z. M1 F. g" I  ask turtles [ set-car-speed ]3 v% B0 O0 v) o( r: F/ z* A' [7 |
2 d) L$ }! v/ \
  reset-ticks! v, }& s7 s7 h9 Z. K; j( y
end- ^% f) Z2 i/ n- H2 {) C1 p
0 ^# J. H9 A5 i6 m
;; Initialize the global variables to appropriate values
/ F% Q. Y" U+ q% O! I9 p( dto setup-globals4 G- j- e9 P/ r
  set current-light nobody ;; just for now, since there are no lights yet( s: m, x) X+ G/ l  o& v
  set phase 0
! f% |7 c1 ~0 K- ^) Y  set num-cars-stopped 0: |) i2 _- y' i2 E% ?5 x
  set grid-x-inc world-width / grid-size-x& j7 E- P4 q, Q- Q4 {: x
  set grid-y-inc world-height / grid-size-y
0 l: P$ O& [, _1 f3 M
, h( H6 G( u: R- J7 G* d  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary0 ]" |, o% _8 h' H$ r. @6 K
  set acceleration 0.099- z4 @0 ]9 q9 S/ r5 h; e
end
9 M8 n1 I" T+ y: L3 @, r: q( X6 a+ `+ W% ^& @
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
" @& H4 a' s% n) T;; and initialize the traffic lights to one setting
9 d$ R  n, Z: vto setup-patches& n6 @" x0 Q$ _
  ;; initialize the patch-owned variables and color the patches to a base-color
& _8 D/ @. Z( B. L8 j$ ?  ask patches7 I: {6 T# Z2 J
  [
. l4 _$ i; }' {  ^7 O! c' w! S5 k    set intersection? false
' n% d3 H( _9 v$ Q2 ~    set auto? false
3 N- r1 s; g4 W9 k* ]8 O0 M) t' q    set green-light-up? true
/ T( n  f" u) V+ P4 V6 X& z    set my-row -17 |& J: s0 s* ?) v; ^
    set my-column -1
( W. y, Q, m4 J    set my-phase -11 G+ v8 `  A4 b5 M; e$ ?
    set pcolor brown + 31 w5 c6 u2 V" U  Q1 V* v4 r
  ]: q0 I$ i: b7 H' Z. {
! O7 ]% [5 }7 Q0 b0 E
  ;; initialize the global variables that hold patch agentsets
" D' s) f" N2 P/ B, m  set roads patches with
% ^0 q) ?8 ]( G    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) j& J. \3 O& m# L/ O* q8 F
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
5 s4 T! X. B# A% i% c( u  set intersections roads with% b1 q2 }$ ?: U( _2 t  W
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
8 h- T) V% ~4 y' K9 q5 n    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]( T0 t. _/ O8 |( M3 i7 M
! l4 p  o6 g/ ~$ P
  ask roads [ set pcolor white ]
# Z8 H, k( _8 _7 U% [' R7 U  ~    setup-intersections3 n$ o: G, m) g9 p' d/ N# n
end" }2 ^% k% z* Q, q
其中定义道路的句子,如下所示,是什么意思啊?
& n4 E5 ^* L4 B* s8 a set roads patches with3 Y' z4 o: M9 a3 l5 r
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or) v+ M: ]7 B. N" E
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
+ S  Q) s2 A" F: b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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