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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$ x0 g% Y8 b% b- i/ H2 a# r+ a
netlogo自带的social science--traffic grid这一例子当中,! i1 U8 R4 G! f3 M- u# n; G1 n
globals1 i+ O: i3 j  S  N9 z& Q* L" M
[
1 G# x) S4 n) w1 M  grid-x-inc               ;; the amount of patches in between two roads in the x direction
. p1 ^- I$ D9 m2 r  grid-y-inc               ;; the amount of patches in between two roads in the y direction, w  k; t& Z9 H! `( E& H& W
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if& _$ q% D5 |$ }1 h7 D. s6 G
                           ;; it is to accelerate or decelerate7 N9 x( G( Q* F  D% o; z7 g
  phase                    ;; keeps track of the phase
$ Q( c& g" ?+ z  Q9 T. W+ H  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure1 s% L& C2 g# G4 X* D$ n0 R: p; R  v
  current-light            ;; the currently selected light  W' F# O9 n8 n# g9 }) ?' }

$ C. A" q6 N8 W3 w  ;; patch agentsets$ I. U, s! ~! u3 B4 c; ?, R
  intersections ;; agentset containing the patches that are intersections) l( S: B' h9 B+ Z) |! Y
  roads         ;; agentset containing the patches that are roads% p) k1 p/ P/ E7 c8 Y0 {# t2 N! I# B3 w
]. R+ U. r8 z8 b% Q% Q6 {3 q
+ t+ a; N, l) [$ j$ Y" p& l
turtles-own; s4 I9 h# f' r4 J/ `' v
[0 O$ J( G' ]' v$ g
  speed     ;; the speed of the turtle8 _* F- F2 C) I- \7 h/ Q7 n7 a
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
% T1 h/ c- o' p6 e( Y0 ]+ J" G  x  wait-time ;; the amount of time since the last time a turtle has moved
/ w! Y; F# i3 A" |, k]' d: o$ t. D* B; N3 G+ X; {# }1 x

4 c! r8 E4 ]) N! W' u+ gpatches-own
4 w4 D5 Q" a1 M3 {* \[/ T# Z5 {* q$ t3 v/ O
  intersection?   ;; true if the patch is at the intersection of two roads( x3 d9 e' i. ?; S! r
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false." o8 _. i8 Y9 K! N  p! r9 M
                  ;; false for a non-intersection patches.+ q! F+ {9 B6 G( J
  my-row          ;; the row of the intersection counting from the upper left corner of the9 Z( h  b. q: w0 k' l5 L# L
                  ;; world.  -1 for non-intersection patches.3 S3 }5 \. d* t9 z+ u9 `
  my-column       ;; the column of the intersection counting from the upper left corner of the( i0 u0 b: K6 a9 W1 ^+ Q% ?. M* ]
                  ;; world.  -1 for non-intersection patches.
1 e* R% x5 `' h& _( q8 m  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.  \* F: F  q# X# n4 i8 G
  auto?           ;; whether or not this intersection will switch automatically.
8 u+ H+ |1 j7 j0 l% h                  ;; false for non-intersection patches.4 ~& L8 l7 p2 F2 v
]+ j/ P9 T% l/ Z4 E& g
: @$ i; p* S" i7 _. \

! c) R) D0 ~! i: v;;;;;;;;;;;;;;;;;;;;;;- l/ V& h8 o. q. d4 p
;; Setup Procedures ;;/ L$ }; [7 O, ]
;;;;;;;;;;;;;;;;;;;;;;0 s9 a+ h4 O2 `( T. ]2 `

. ^- ]# @0 v9 r: a;; Initialize the display by giving the global and patch variables initial values.
5 x0 w% V1 X# u0 Y5 J;; Create num-cars of turtles if there are enough road patches for one turtle to
+ g5 o0 ~. K7 h; R* B;; be created per road patch. Set up the plots.0 [, d5 i6 B& t1 [! S9 C9 U
to setup
0 ?  R7 X/ s: u5 J  ca
* S6 E' o4 d) j  setup-globals5 r7 [3 D$ P7 k/ J; `/ F

% L. E# p6 s. N9 p  n  ;; First we ask the patches to draw themselves and set up a few variables
2 r0 N2 A0 c, d! |! r  setup-patches
; `/ {4 W7 A% ?7 y. z7 c  make-current one-of intersections, M3 p, l9 d, \
  label-current7 K( A5 @1 A3 ~: A, j

8 b) B: V8 r( j  set-default-shape turtles "car"
$ |6 m) c$ G! y- I/ J% s1 e* m1 S7 T, f2 [+ r
  if (num-cars > count roads)5 I9 E1 \% j7 l) [3 s
  [# d/ Q, ~+ d2 @+ r  Q6 B; E
    user-message (word "There are too many cars for the amount of "+ m! y) c1 d5 }& Q* y
                       "road.  Either increase the amount of roads "" K' J* Q$ m: D) ~$ h- h
                       "by increasing the GRID-SIZE-X or "7 s! \& b/ \, Z
                       "GRID-SIZE-Y sliders, or decrease the "
% d- W' v- g  M                       "number of cars by lowering the NUMBER slider.\n"
1 d! }' `2 O% n0 A$ g7 \                       "The setup has stopped.")
1 w- T/ F% {* ?9 R; o' r    stop
; W. _/ z" T9 T$ Q' R0 z  ]
/ v+ w0 B, @4 ?8 ^( w3 w2 L
& J: g$ y* f6 Z7 h' ]# b( v/ G( E  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
' g  _3 B9 j* q/ S- j* ~  crt num-cars. e& e3 X5 p4 K; @
  [% b  e6 J7 i% B# r- S6 o3 A
    setup-cars$ P, ^" j" m5 ^$ O
    set-car-color
& C4 u% ]& G  E/ j" {    record-data  K% G( M' w. M6 q8 [3 r
  ]: K3 I3 ?) M( t- f: p( M
, q+ V2 t' |  V" K2 \1 d
  ;; give the turtles an initial speed
  _% c% ^4 H+ r' X7 e/ f  ask turtles [ set-car-speed ]
+ t. W" q% H9 `. T9 B- X0 c% s
! ~, r) O( h' `% N6 x3 w  reset-ticks: m! j. H7 B" h; i
end
+ Q) j! t/ l. v; n. c* D* s
2 l6 Z0 b2 `- }/ O$ A$ e6 `5 t3 z;; Initialize the global variables to appropriate values. v' Z2 K4 J3 J; Q: n  e9 {5 {0 _
to setup-globals% n7 J7 ]; C- [7 S1 e/ G; Z
  set current-light nobody ;; just for now, since there are no lights yet/ g4 h8 `" k8 X  i( M
  set phase 0
8 ?. K- U$ h4 Z! t6 n' Y  set num-cars-stopped 0
6 H. X# ], D" L% y  set grid-x-inc world-width / grid-size-x% I7 S8 V: z2 M
  set grid-y-inc world-height / grid-size-y5 _/ U1 e+ w# }% v+ a' q% A

% J8 ]' {# B# k" L  [  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary" J* ]2 j* w. V! e
  set acceleration 0.099) u* U; a9 v: v6 w+ b5 E1 {# x) h
end: t3 v9 _& j7 v/ u5 X9 |2 ^
/ @" t( V# u/ S- B- {
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,; g! {  w) M% U6 C/ G% e! V# s
;; and initialize the traffic lights to one setting$ V9 Y! k6 ^& i3 {* W/ z: w% }& a
to setup-patches  f; ~7 R8 I0 G
  ;; initialize the patch-owned variables and color the patches to a base-color
5 ~6 U5 x: E4 C: \! p& g  ask patches
3 p; W4 k6 L4 {  [" F; H# I  I) p7 p$ a2 r8 k
    set intersection? false/ T0 e/ O$ p! W* k! g$ C: @7 Z
    set auto? false) `0 T0 i, G8 _) X3 Q% Q, a
    set green-light-up? true
! \! i. @/ E" P4 [. G; }9 X    set my-row -1
! f8 }  w5 L8 g) N' a    set my-column -1
5 `# u" D  J3 j" N1 a; u    set my-phase -1* Z8 y7 E, m7 W1 f
    set pcolor brown + 3- X/ d/ ?, t" s+ ?8 [5 |( B7 o
  ]
; t" A( s  m4 u: {0 n2 n6 d0 C( L4 N# F' {2 J
  ;; initialize the global variables that hold patch agentsets+ @) `+ B6 d+ r3 ~
  set roads patches with8 j* \1 D  n. j, H/ `" C4 p
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
4 J  N/ X1 h5 v6 s0 H/ a. w    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]: c( R" b7 H, e3 O
  set intersections roads with
$ i$ g) l" t8 w5 _: P  {    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
5 x3 L$ R% o( O5 ?# W9 Y) @    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]; J  z+ A" R, Z$ `

' [. M; s$ `, X7 D  ask roads [ set pcolor white ]. F* T4 U2 f* _: E) D7 A
    setup-intersections6 ?- j% g4 @  I1 b& x) B8 Q) b: N
end$ @% c: X  X, V$ a# R0 f0 ]9 M
其中定义道路的句子,如下所示,是什么意思啊?
; x$ W, s: ?. f& I( a, ?  A set roads patches with
  j% \6 E5 @' u! d' n    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or5 ]8 X4 [+ x7 {$ u
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
. j' u4 U. {( d0 I$ u( o' y8 Q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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