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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。
+ h0 m& n; V- B$ R( L8 Snetlogo自带的social science--traffic grid这一例子当中,
6 `$ x1 A$ n+ gglobals% S2 `* C7 K/ _  t: t# }
[
7 e/ m3 E4 c4 _9 p4 o+ n# R: [  grid-x-inc               ;; the amount of patches in between two roads in the x direction1 p. R$ I7 O2 M" F
  grid-y-inc               ;; the amount of patches in between two roads in the y direction, o( }1 w- w) k& V+ V6 T( N
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
7 y7 }2 B) U+ `  S6 ?# R                           ;; it is to accelerate or decelerate
" q( |+ Z: |, a" ]& Q+ K  phase                    ;; keeps track of the phase: g( ~5 U, {( T" C; ~* |
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
" y  {7 f) D  g8 z$ {3 n  current-light            ;; the currently selected light* N5 t+ t8 Q( K; q6 \/ Q1 v
; X$ G/ L1 Z$ a# C" r) }
  ;; patch agentsets
$ w2 h. M) T- {1 f3 X  intersections ;; agentset containing the patches that are intersections" G- p; x; X. H+ `" E
  roads         ;; agentset containing the patches that are roads
/ L1 F7 z- u) c6 F- q: K]  g+ |: }$ y+ f. g& |6 z
/ e5 D" h# S) d
turtles-own+ D+ e- @# {, }9 f  N! [  P( u
[
% U3 Q* T# r6 v# J' J* W7 {8 B4 Y  speed     ;; the speed of the turtle
% A! }2 G7 z* T  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
0 |+ {8 Z* E/ @2 d+ k0 T, S  wait-time ;; the amount of time since the last time a turtle has moved. m" U& t1 k  h
]* O/ I0 A# I" t% i2 w

2 G' m1 \# S0 e0 G9 [' Dpatches-own
, c% ~/ P4 ]; U/ e1 ]! b[
$ r4 l5 c$ f- T0 Y" x  intersection?   ;; true if the patch is at the intersection of two roads% T7 |" h& T$ j% a. x1 `8 L
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.) F4 Z% |  z6 T2 ~& w4 l
                  ;; false for a non-intersection patches.3 p' W- N& p) U6 m' P" K
  my-row          ;; the row of the intersection counting from the upper left corner of the
% t1 T3 G4 M8 ]; g; s                  ;; world.  -1 for non-intersection patches.
" X1 \/ ~1 C. }+ r' U* e. Y  my-column       ;; the column of the intersection counting from the upper left corner of the
5 t, @8 G$ p3 v: T. c. b8 ~2 {                  ;; world.  -1 for non-intersection patches.
1 R! x  _0 f5 ^: l" h5 }  c$ x  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
  C2 y! n/ p, P: f& T% m$ S  auto?           ;; whether or not this intersection will switch automatically.$ h7 `3 ~1 l5 E6 ?& v$ P
                  ;; false for non-intersection patches.9 w) y$ v0 N7 l0 a4 g
]
8 [, o0 \, E% K7 d) m8 y/ W/ m" ?" y: q- w/ q2 L: e
8 H$ i) K, T1 w5 Z
;;;;;;;;;;;;;;;;;;;;;;6 _$ N: z  z+ B! U4 ^8 E  h
;; Setup Procedures ;;7 E/ M1 s; i& B/ n
;;;;;;;;;;;;;;;;;;;;;;
! {3 T. o, \! U) Z
+ E' |% L( w$ t) W;; Initialize the display by giving the global and patch variables initial values.
9 `3 o% ]% i  ];; Create num-cars of turtles if there are enough road patches for one turtle to3 R/ J* c' H& Q+ F0 z
;; be created per road patch. Set up the plots.
* x' Q3 h: s$ b* Z, M) q  z1 gto setup$ @" M( f' k9 ^4 e+ @& e$ Y2 F
  ca2 I4 Q1 T  F# f7 r1 \
  setup-globals$ w1 b: \! u, i/ k8 P
5 L) [+ F* t' i" g, h
  ;; First we ask the patches to draw themselves and set up a few variables
4 [  `  w2 X& n  setup-patches
# D, H* ]$ d8 F. ?  make-current one-of intersections' P' V/ b  N* _$ B: R
  label-current. {" X/ p" Z( V0 b1 x5 ]' W* B# p" D

, V8 N' N& a! R  @  l  set-default-shape turtles "car"
& H; ?. h) U2 q3 N  }# O# }9 c  ?0 z+ o8 c+ a! v4 c3 f: _
  if (num-cars > count roads)& |; T  C8 F5 B* s1 R# Z6 r
  [
" B6 q& o4 k% b7 |/ R    user-message (word "There are too many cars for the amount of "
( T  `; o- u" c( R3 _1 ]                       "road.  Either increase the amount of roads "
" ^% {- h( S2 y) @2 e7 I                       "by increasing the GRID-SIZE-X or "
( `  T; o- O* n6 J+ N! m+ j7 K                       "GRID-SIZE-Y sliders, or decrease the "
) c  \) G: u$ n/ a4 y                       "number of cars by lowering the NUMBER slider.\n"
1 C+ u. G1 e0 a; s, n& v                       "The setup has stopped.")
* X/ g! W5 C0 ^9 c# P    stop
% G" w4 Y; V, o  ]8 A8 [1 t0 i1 j- K7 W) o, u5 ?

2 R4 @7 _# c+ C' E; e  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
( m8 e' T$ e! F7 i) P5 d  crt num-cars8 R1 |7 E+ I0 k* U+ G( B
  [, |4 E" @3 g/ h
    setup-cars
7 A* o) \7 P7 D! F    set-car-color
! `5 B9 J6 a6 a+ m5 T$ L    record-data3 {7 P9 t0 K/ [1 r8 |4 D& a
  ]
( s8 T- e+ k% o1 Q  x% N& k0 o2 u- G1 z' ?& y+ [# V7 C
  ;; give the turtles an initial speed8 M3 x) H6 {$ O. G
  ask turtles [ set-car-speed ]
! {7 {3 g+ L! v! F$ z# v7 O  c) L3 u0 x
  reset-ticks$ U1 l. N& [2 o
end- h5 n' H2 o) ^% K

! H2 g: b) Y) t$ F;; Initialize the global variables to appropriate values
: I% R/ a: S6 ^1 |# g$ _, A2 k8 M- tto setup-globals, p; S7 L$ v, O9 L4 i% d0 Q+ o
  set current-light nobody ;; just for now, since there are no lights yet
' \2 E; Y- @- c7 z, R  set phase 0
* P! T7 ^0 q5 O% Y; T  set num-cars-stopped 09 C9 ]# e3 T% C7 j! E3 T2 j, l/ i
  set grid-x-inc world-width / grid-size-x2 D( O+ B, v, V8 A% ^# X0 c
  set grid-y-inc world-height / grid-size-y
/ _- I0 p6 m7 k8 I! f& M" Z* q; @
$ k4 ]) l6 t- Z  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary8 w2 v# _; n+ s6 W/ ?
  set acceleration 0.099
5 T8 Q) @5 O0 U- ^end
- Z2 f, N- f3 a: |" u( ]% c+ X
" w3 s( f2 Y3 ~4 m1 V: L6 R;; Make the patches have appropriate colors, set up the roads and intersections agentsets,& E# \, ~4 w8 I# ^: G
;; and initialize the traffic lights to one setting& g6 ?6 o* l$ h# J+ z8 T" {
to setup-patches
1 H' v7 V1 O6 |$ I& }/ `% S  ;; initialize the patch-owned variables and color the patches to a base-color
4 O- _# T% Y8 p' C( C  ask patches( v2 r7 y" D: p0 P
  [( P; [" G9 Y* M" f6 C1 k3 W; K$ Z
    set intersection? false
5 u3 Q* f1 Y" T  Z    set auto? false
2 H& i6 c# N9 i8 [% c& n    set green-light-up? true
, k2 a  h( j3 M3 l" V$ f, k    set my-row -1
7 V( `' F, z* S$ C/ D    set my-column -1, R% a2 D# h$ G2 u6 z6 j
    set my-phase -13 ~7 d- R$ P( m5 q/ b. ^
    set pcolor brown + 3. J$ F1 p5 T" w0 |3 D+ e0 ^2 V
  ]0 N4 P4 d5 z1 u, Z1 T

" |+ x- _. j; l; [( Q8 X) M  ;; initialize the global variables that hold patch agentsets
& t3 B& C4 u- _  set roads patches with5 h- A+ S8 _8 t4 r
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or2 Q% r* A( V0 G5 n- X* \6 u5 F
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]5 p# ]2 o% e  P. K1 _% c
  set intersections roads with( m7 R( {  z! E+ ]  Z8 a4 H8 [
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
1 e& O3 B: L9 w    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]8 e. o, k( r0 {7 M4 c  U

  T& L; V! S, Q  ask roads [ set pcolor white ]) i5 u$ d; q9 C  ^2 Q  |/ d
    setup-intersections
( S& K" ^- C1 X& d% ]" V0 R3 V" Hend
  C1 k7 U2 h: N其中定义道路的句子,如下所示,是什么意思啊?
# N2 ]3 J. Y1 D- E2 Y1 S0 a* ^ set roads patches with
: [* M: u0 y( a, A    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
. w  u* t  h' q/ P' u9 g: I# A, V1 q    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
( ?- [1 K: e" X4 ~2 y% ~4 q% S. E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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