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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。- c+ g3 N. v; d9 F
netlogo自带的social science--traffic grid这一例子当中,
$ X- Z0 E, \! d0 Y- A( e5 H; nglobals
! @7 p& ~5 F! `5 D- F7 G[: t8 }$ C. R1 ^' ~9 d: N, E
  grid-x-inc               ;; the amount of patches in between two roads in the x direction0 U0 b# C; T1 c2 Y, l
  grid-y-inc               ;; the amount of patches in between two roads in the y direction/ \" T7 a( J/ R  o3 h
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
" i* x8 H" Y/ }& Y6 b& V                           ;; it is to accelerate or decelerate* ?6 X! D4 c, u. b2 G* D
  phase                    ;; keeps track of the phase2 j+ n  J5 h$ C. R
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure( G4 J+ u' u, s; Y# j  H. t% q
  current-light            ;; the currently selected light
: y  y8 A4 [( X& e) N
; ~6 l( t/ }# ^% c' X+ D  ;; patch agentsets; l: ]/ I5 B' x' i' ^, E
  intersections ;; agentset containing the patches that are intersections5 w: v7 j; V" j; j: Z- W7 ~
  roads         ;; agentset containing the patches that are roads
0 M7 `" E5 o: H5 {% k]
  J3 c; d6 V, L9 W, W8 t, U5 y( k1 T& t( E5 M$ k
turtles-own
% X1 _0 Z! m' y[$ ?7 l$ v: U" f/ L) k7 S5 w
  speed     ;; the speed of the turtle
5 {8 X4 U! X3 M6 n' h& @  up-car?   ;; true if the turtle moves downwards and false if it moves to the right) M" a8 b  @/ V! }  A. `% k5 D
  wait-time ;; the amount of time since the last time a turtle has moved
6 t, k) a: u: T  @* d, w" {]
& c, E( E- @9 X& T+ c  [' x# q( R& n8 r; |* V9 J( s( i+ H* [0 t; K# \$ N; {, B
patches-own5 a. l0 N4 w) q' s
[
! p* Z! E& M/ [) N1 z5 Q& Y7 F  intersection?   ;; true if the patch is at the intersection of two roads3 C; u) @+ x; y9 q" {8 N0 u+ z; w
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.) J/ y; ?9 \0 O2 W8 s/ E
                  ;; false for a non-intersection patches.
8 A" w  T7 [# U  my-row          ;; the row of the intersection counting from the upper left corner of the( J8 J- _5 g  |4 |3 s
                  ;; world.  -1 for non-intersection patches.
8 h' v1 M' ]/ U: S  my-column       ;; the column of the intersection counting from the upper left corner of the
0 ^' \$ r: |# a) D; ?+ {                  ;; world.  -1 for non-intersection patches.0 P# z1 F! p0 ?  P# S
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches." k7 k( e- g' `1 L( l3 e
  auto?           ;; whether or not this intersection will switch automatically.$ b' P* q! W" E+ R- r
                  ;; false for non-intersection patches.
" d; w! J- W8 ^  u- \3 p]
& C, Z) y+ d  E
" x# j' n1 T& H! K+ j' t) Q6 Y8 Z' i9 `2 O4 [
;;;;;;;;;;;;;;;;;;;;;;
. L; e) n( h) s! o;; Setup Procedures ;;1 R' A& ]$ T7 R1 ~
;;;;;;;;;;;;;;;;;;;;;;# j! `/ e6 X* J* [' V0 m) p

* x* `! a& F2 `;; Initialize the display by giving the global and patch variables initial values.
! [. W1 W4 b$ F& `* C;; Create num-cars of turtles if there are enough road patches for one turtle to$ s; [* `1 \3 M' j
;; be created per road patch. Set up the plots.
1 q. v& @  ]5 e0 c3 X3 q  P( g4 Oto setup- c  ^) ]) u; t. k- w! g
  ca; M3 a1 U3 i5 X' y
  setup-globals2 L+ i5 k% F9 x; B5 @  _
+ k: u: e: W: s, B3 Y
  ;; First we ask the patches to draw themselves and set up a few variables1 k6 I8 m! i% F: B6 `/ v& x
  setup-patches1 B, |' n  N0 M; y
  make-current one-of intersections) g4 G: h( J! P6 ~
  label-current$ Z& i! S& S2 r0 s5 \/ ~6 S

( b) Q  g! N4 [. x: W6 ?9 I  set-default-shape turtles "car"
- z+ G: {& V) N/ c2 R+ z3 x. v: Y% o3 u( B' S
  if (num-cars > count roads)
% H/ @' \; S  N$ ^* T( v- Z" m  [, t: z# l; q) ^  w
    user-message (word "There are too many cars for the amount of "" B; A* p+ ]. u/ g3 I. _+ A
                       "road.  Either increase the amount of roads "
+ A( a$ p7 s, C2 x) P$ l                       "by increasing the GRID-SIZE-X or ", W( b& u$ b) w! j7 C
                       "GRID-SIZE-Y sliders, or decrease the "* p' [( ~; J% Z* s1 c
                       "number of cars by lowering the NUMBER slider.\n": g4 B. U$ O5 ^/ ?6 g
                       "The setup has stopped.")
! s( W/ D/ N% x( V    stop
. G* U( t2 O1 V% @) _  ]
9 @; |; w  {) ^' P* B6 Q- L+ w* p9 ?3 |1 n3 z
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color! M9 l, r; f6 S" t" z
  crt num-cars
$ B9 K4 `$ A" c# E  N  [( u9 j* T5 T7 @* f3 B9 o5 U
    setup-cars( S  X* K. q2 t% C" D
    set-car-color( u/ H: W7 L) d$ Q0 `
    record-data
( h1 ?- V) j3 ]2 r% P& H* o  ]
1 s# x* j3 |* E$ {  q; F  k  e9 u
0 ]& V' y7 B3 B* U: ~- I  ?  ;; give the turtles an initial speed7 c+ J' T% K3 l$ ~6 V- ?) [
  ask turtles [ set-car-speed ]
, E, r) v7 ^$ Q4 l4 n1 o
5 Y% |5 Y- D/ G' y& F  reset-ticks9 X4 E4 s6 J1 x
end
, g) v+ g0 }" e* l: C, X
0 C- g  f4 N' Y; P% N1 V( Q1 j;; Initialize the global variables to appropriate values
1 U/ Y1 y& [5 R6 Eto setup-globals+ t7 N0 d) H' Q9 d
  set current-light nobody ;; just for now, since there are no lights yet2 U+ d  y; l3 D$ c* p. i
  set phase 0) K9 W) S" P; g+ P5 a4 X" _, P
  set num-cars-stopped 0
% d4 m7 k! y5 E. R! ]) `4 w. P( D: H" Y+ E  set grid-x-inc world-width / grid-size-x
& c: z# t9 Y( r4 h6 x7 d0 X  set grid-y-inc world-height / grid-size-y
1 X5 X, C# V0 U% f$ H
& I5 ]/ x2 `& Q4 i  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
& M# y5 h' c7 s8 L1 {* S  set acceleration 0.099; x! B" C: l- a
end
" T3 j9 ~$ M! N. m
+ F1 b0 G% ]/ J4 P: L& G4 v;; Make the patches have appropriate colors, set up the roads and intersections agentsets,! {8 \( P1 g+ A% s4 a. Y
;; and initialize the traffic lights to one setting. M/ X% u: G3 Z# y+ b+ x3 I
to setup-patches
- y* q( e* ?! a' }' T1 R: H  L  ;; initialize the patch-owned variables and color the patches to a base-color( C4 ?4 R% K# Z' I5 }/ s4 Y% Q/ _
  ask patches
8 b% |( ?0 b4 A; V: r; y  [
: f, B$ n/ ]) V/ G    set intersection? false! `8 `; T9 F1 i% V
    set auto? false
9 P4 {! D& ~8 g    set green-light-up? true3 T6 @' }: v0 m0 X3 K/ Q
    set my-row -1- e& t/ a! n9 ]4 u$ g
    set my-column -18 q6 I/ p0 v1 o# j7 X9 H9 v
    set my-phase -1: ~% R) {6 e6 p2 U
    set pcolor brown + 3/ H9 o& s7 q! L9 f
  ]& p, T) X+ ~8 a2 c+ K2 C6 L

, c6 a' P: g% u. Q! y- e+ L2 i% U+ e  ;; initialize the global variables that hold patch agentsets% j! m+ s/ m& V* M% ]
  set roads patches with: x. i& g/ \% V& ^8 c
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
( |9 l5 V/ {3 t4 g) h% O    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
2 i0 L! I5 ], y0 }: X9 u% Z  R  set intersections roads with
+ L3 `) {" G- {6 a9 Q    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
1 V3 L) Q1 q. v# F; C' ^    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]8 h1 z: ^% Y% v' _8 O! P- A

! X4 @4 ~# Q: K- b; L  ask roads [ set pcolor white ]0 r! k3 u" R& Y/ K: p/ n
    setup-intersections
+ D3 c) s% v" z( @( bend% X$ S0 M. S; R+ ^
其中定义道路的句子,如下所示,是什么意思啊?
, H8 p, t/ Y0 U  _ set roads patches with
% r! v5 q1 B, M2 Y! c. W+ P    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
/ X1 x! B4 I" Z, [% K& H7 N    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]+ g% c9 Q) e8 l, F; 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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