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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。
: L1 L$ d/ c" ?4 Qnetlogo自带的social science--traffic grid这一例子当中,
& M; O& z, o' G7 ^globals& ~: N3 S  g# \
[6 ~5 H, B. g, Y1 y& }
  grid-x-inc               ;; the amount of patches in between two roads in the x direction) H) b; _' R" V- R$ i; [2 S
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
  E- |! g7 B. C1 B. A  acceleration             ;; the constant that controls how much a car speeds up or slows down by if) Z0 e& f3 S  _6 J' J
                           ;; it is to accelerate or decelerate4 x, e* n, y. K' }+ J
  phase                    ;; keeps track of the phase" n; a% K  g( R/ {. k$ N) Q
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure! _' K% A& m$ k' v/ j7 T
  current-light            ;; the currently selected light% s9 [+ R7 e! b) K$ H* F
7 J2 X& R6 p$ O
  ;; patch agentsets5 W% p3 B! Z' a6 T# a
  intersections ;; agentset containing the patches that are intersections
9 J* V0 W  f2 i" O* g5 i. t+ C2 `  roads         ;; agentset containing the patches that are roads
4 V- p% }) E8 T. Y4 i) L" {& M], @6 X7 m9 _! m/ f8 M' r9 k' l  f
' i* E0 M/ ~9 q! y+ p+ k3 g
turtles-own
8 m% b) \( a% e) }, V5 M[
. T8 n8 o$ Z' p; N& W  speed     ;; the speed of the turtle3 J& k, R: H. \; D$ i' a
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
, m6 f- x+ Z# u. I1 Q3 \$ S9 e  wait-time ;; the amount of time since the last time a turtle has moved. f* f$ x" _4 h8 r! M6 s3 U2 B
]0 e4 L& b8 m6 e7 s

% E+ t- @  c- L9 K3 x9 Mpatches-own" G! A, M) V' t( r3 H- e
[6 X4 J+ O) h* U
  intersection?   ;; true if the patch is at the intersection of two roads
/ {7 p& @  Q! _! t. J7 R' A# s7 S  green-light-up? ;; true if the green light is above the intersection.  otherwise, false./ t. B+ L+ V" Z5 ?1 ~- y3 U
                  ;; false for a non-intersection patches.* L  r6 W. ?+ T$ Q$ ~
  my-row          ;; the row of the intersection counting from the upper left corner of the
6 u! s# E$ a9 X. W' t# D) d% s3 [/ z; Y                  ;; world.  -1 for non-intersection patches.1 Q) n. e& Z; p) f7 e
  my-column       ;; the column of the intersection counting from the upper left corner of the" A2 Z2 I7 I: X
                  ;; world.  -1 for non-intersection patches., N% ?. Q. }2 I/ i  ~( M
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches." y, s% x9 j8 y9 ^- G5 Y
  auto?           ;; whether or not this intersection will switch automatically.
3 l: J% v9 P6 b                  ;; false for non-intersection patches.2 `6 \+ l) p  m* O7 R! a
]7 u; m) G& D7 F& Q

$ T0 }- F/ ^) R$ U  @- A! B
9 O0 K0 d/ H$ V) l" }& y;;;;;;;;;;;;;;;;;;;;;;  J7 d  }* a& o
;; Setup Procedures ;;
' W" }6 r- X: a;;;;;;;;;;;;;;;;;;;;;;
. b" D7 |) Y8 V8 n; i& f/ _* |% b+ H3 w7 M
;; Initialize the display by giving the global and patch variables initial values.) U0 X8 z& Y: P
;; Create num-cars of turtles if there are enough road patches for one turtle to+ T  j4 r/ T7 P& _0 q5 W" H
;; be created per road patch. Set up the plots.3 u4 o4 u$ b; X) ]
to setup- o  t/ D/ ~4 s
  ca
; p  x) p* j& p& N+ Z0 N$ y  setup-globals
* ?" w( ?: h) u; @4 y7 D- b& b" j2 k! b. S
  ;; First we ask the patches to draw themselves and set up a few variables
% }8 }" N$ ]. n- D" z6 Y  setup-patches
0 Q9 G& M( p' ]) U( n  J  make-current one-of intersections8 H2 h6 O' w) Z5 S
  label-current
1 f: a) _' A/ q; s6 t$ i8 w+ C9 U0 v% J, ^
  set-default-shape turtles "car"- R3 ?1 Z9 }0 h2 B/ o: K
$ I* b/ }5 A8 |* L. M
  if (num-cars > count roads)
, e3 I/ v  I" R: A3 u3 H$ X  [
/ L# ?$ [" f7 H* O. K5 X; `    user-message (word "There are too many cars for the amount of "6 z, L1 e0 Y* S* @$ j  E% q
                       "road.  Either increase the amount of roads "7 C: \3 X5 H' g$ A- w# P
                       "by increasing the GRID-SIZE-X or "
/ s5 k- `- @+ `! K6 M/ j                       "GRID-SIZE-Y sliders, or decrease the "
- _8 e. l3 @& k) c$ u* q                       "number of cars by lowering the NUMBER slider.\n"2 B* n6 R% l* g
                       "The setup has stopped.")
  q# |$ Y# N: A( z    stop" q, S) l, Y/ s+ Q- v, h6 k- _0 C
  ]
) C! r2 ~8 g7 `; C! W  m/ r
4 o6 P2 o! P( p# V  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color+ k  i" z! I8 [
  crt num-cars
1 G4 Q4 l7 ?" L7 x5 w) I% B, c  [
0 C: i5 U4 }  D) ~3 v' F2 `    setup-cars& k/ B* @1 q* q
    set-car-color4 G* L. R/ g# K1 ^+ _! p
    record-data. N% Q6 \& {' H% B
  ]/ [) S" L  `3 a3 Z: g
% e. W( S' P! p4 |9 ?
  ;; give the turtles an initial speed
. T# T5 D: f% N" `2 n( k2 [  ask turtles [ set-car-speed ]8 U  u$ I% g8 ^  a, P8 u. w
6 f- Z% P. q9 o: \' d% t7 M
  reset-ticks
, h. b) W' [# D. wend
) X9 R9 M2 |" B/ s  I  S
- U2 R5 p2 Q! j' q# U/ X' y;; Initialize the global variables to appropriate values
* I8 D8 b" ]+ z9 @to setup-globals
9 a! R( v8 b6 d% U  set current-light nobody ;; just for now, since there are no lights yet
& _( J( i' r  R* o0 X) S' ?2 n( k  set phase 00 a! A; j4 [4 U$ |
  set num-cars-stopped 0
7 j' H6 {- I5 K! Q9 ^  set grid-x-inc world-width / grid-size-x/ }$ B  g5 M9 j. E' i
  set grid-y-inc world-height / grid-size-y
& U! N' r2 ], y- G
) l' s) O! q0 j8 @8 y  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary) l8 o; o9 |* H6 X  T
  set acceleration 0.099
. }* m6 s0 Q; a( @1 Bend
' B+ j& M, B2 V. [
4 Z5 P9 P/ ]$ {;; Make the patches have appropriate colors, set up the roads and intersections agentsets,  `. V' p8 f5 o; h  h  v# S
;; and initialize the traffic lights to one setting
5 [: w3 I7 ]* Qto setup-patches
' G1 \3 W, S( j. H$ Z7 P  ;; initialize the patch-owned variables and color the patches to a base-color0 P/ H8 Y# e5 G2 i9 s4 _& P0 f
  ask patches
3 O* B6 }- ~$ K( B9 i$ v  D  [
- K. F5 v. Z$ E7 S; [1 d  f    set intersection? false
7 @6 u8 U5 ]0 w( j' Z( N2 W    set auto? false- Q* U! T3 ?4 P' O+ B2 A" I9 b
    set green-light-up? true
8 ~, P. F. b& R( E1 N7 }# D    set my-row -1
9 q' b) n1 L7 z/ E    set my-column -1- p: m% ^* E; D. b- W
    set my-phase -1: u" ?/ g1 B  x
    set pcolor brown + 3
, O: C. G$ m' k5 f8 p+ p( m  ]9 n2 y' g8 [; t* r6 g5 r$ F7 p

' j, ]3 s* x5 F4 z! j  ;; initialize the global variables that hold patch agentsets9 m8 R- l1 w6 M- u
  set roads patches with
4 j' V. @6 F+ e% U( D3 n$ \    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
7 W5 {; |$ Z. y4 `5 C- ]    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
( G& I. ]9 m5 i1 Q( h  set intersections roads with' v( y) {2 r, f0 K
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
0 U0 Y% `( `, ?' k- d2 ^    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]& a0 S' C- d$ h' d' T! m0 a% _

- N3 f* g. U1 ~# V# a& a  ask roads [ set pcolor white ]
  @1 n+ P; q- i" g8 Q5 p& ]3 Q    setup-intersections3 y! u$ F. i8 y
end
0 Q2 p8 J  K, m其中定义道路的句子,如下所示,是什么意思啊?* p0 A/ ]: g# [( D
set roads patches with
1 {* ~7 {8 s, g, I1 @    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or5 \! q2 L  S/ `! q; [
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]; f% e- F* e6 W9 E) A
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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