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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。' y( g7 E9 p; \4 L7 J. H3 U8 V' j
netlogo自带的social science--traffic grid这一例子当中,
0 T) u% l0 r; ^! S4 m: Bglobals
# L+ u" P) w7 B3 g[2 j  f+ |! g% W6 `
  grid-x-inc               ;; the amount of patches in between two roads in the x direction
+ @+ O! s% o# u2 \  k  grid-y-inc               ;; the amount of patches in between two roads in the y direction$ W; P3 v. c6 j1 e* v6 T
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
" B; W9 e: C% i) E+ K                           ;; it is to accelerate or decelerate
. o; E+ z  }% P2 t. ~  phase                    ;; keeps track of the phase4 M* L# z+ h) _# l! b: [
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
! d: R* h/ C7 m3 E8 v- M  current-light            ;; the currently selected light" a) D# h' v+ {$ g! |0 ^3 i

: o3 t  A- X6 x0 Q* j) S/ @  ;; patch agentsets' B" g  N( c) ]& D
  intersections ;; agentset containing the patches that are intersections2 C  U+ |, b' S* _; p$ w7 {
  roads         ;; agentset containing the patches that are roads
; L- Q/ c9 Q& ~" G! Y, Q) J]7 ^* j" R- j" s. k
* |5 i, {9 w. f
turtles-own) u/ z3 j0 {! D9 M
[
5 V) a+ }8 S" G) c4 x' b2 a& L9 ?  speed     ;; the speed of the turtle# \+ N. U' h7 u; O! G0 C7 w
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
' o* b* g2 C% B' d3 d  wait-time ;; the amount of time since the last time a turtle has moved" U- B9 g3 X1 W
]
+ e! A$ @2 j. ^0 l( Q; R9 t3 [
# A/ T2 z+ }& f% y7 X5 _3 s9 hpatches-own4 i& t' a3 A  `
[
. \  W1 f' p0 p2 q. J, }% v' {  intersection?   ;; true if the patch is at the intersection of two roads+ i# ^7 p% P8 c8 N# y
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.8 t+ u0 a; M9 V- J$ P( x. h
                  ;; false for a non-intersection patches.
% f- L4 Y! U' {  my-row          ;; the row of the intersection counting from the upper left corner of the* h8 R4 r3 V, g7 K% [8 F! U
                  ;; world.  -1 for non-intersection patches.+ {& x! y1 e0 S5 u
  my-column       ;; the column of the intersection counting from the upper left corner of the
* g* E% K* U% C$ a! R6 g                  ;; world.  -1 for non-intersection patches.1 H8 s# f' G$ Z' f! Y
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.! J6 Q  d# m0 P4 g+ G# b  L& S
  auto?           ;; whether or not this intersection will switch automatically.
  J! t3 n- h& b                  ;; false for non-intersection patches.
* [* j8 v- ~9 Y0 s$ o- m- ]! I, z]( A9 G) p3 E) P& t- f
' U: j  C, P& z
- O9 Y/ F2 t; A/ w, x# ^
;;;;;;;;;;;;;;;;;;;;;;
( _5 U$ e2 Y6 b5 w. g;; Setup Procedures ;;
- A" p; t( p1 z( a" X% {( ^;;;;;;;;;;;;;;;;;;;;;;
8 o3 _+ u' h' k9 _. Z* U3 I( K0 E
* J* @, C% X8 f6 e$ C;; Initialize the display by giving the global and patch variables initial values.
1 H0 C7 X  ?" B! `;; Create num-cars of turtles if there are enough road patches for one turtle to2 g/ G- |8 R6 K6 l! G
;; be created per road patch. Set up the plots.
/ O. U- }5 t2 z1 Yto setup
8 `# v0 I1 I5 m  ca
, W0 P6 D) \$ k  setup-globals
8 {5 V) i- |4 r5 ]0 I% M: q8 b: `! D3 o) P$ L' n8 c% ?
  ;; First we ask the patches to draw themselves and set up a few variables; ~* j1 ?6 e* M. @
  setup-patches& `. p" c" N* D6 O. x- e% _
  make-current one-of intersections
  K! c$ s* ^7 j) L. o, E  label-current
7 K5 l6 _: X! e$ x2 |; j
3 [% s7 e) f/ N  set-default-shape turtles "car"& E- t, k5 @; t

6 N" n! J$ P0 q& H3 G6 L) l3 R  if (num-cars > count roads)$ D( V! b! J2 \9 x; k
  [
# S( _% n& `+ [/ c9 S, }; V/ Y    user-message (word "There are too many cars for the amount of "
' Q0 _8 T  `: P( `                       "road.  Either increase the amount of roads "! e( B5 x9 z6 E2 S* L' ]' H. c( y/ h
                       "by increasing the GRID-SIZE-X or "
$ ^  h) }0 C- x3 b7 h$ Y                       "GRID-SIZE-Y sliders, or decrease the "( V4 s8 E7 O4 g/ N
                       "number of cars by lowering the NUMBER slider.\n"" [7 i& K' l; ], w8 a6 x' v
                       "The setup has stopped.")1 j+ A6 G2 ?) U
    stop
+ [/ ?: I& _( s7 \, K' Q. _5 o  ]
7 M8 f& e# _. B% y3 b, t' N, J" \1 r0 [
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color3 R7 I. j6 J2 o9 M% m* u5 A
  crt num-cars; j7 b$ t0 ]4 ~8 p
  [6 m. _8 k" }6 U0 v
    setup-cars
$ W0 ?0 G( {* x! h( x    set-car-color7 r* G: @# Y- t4 _( y
    record-data- \! h% N- x1 [) v
  ]
- a) _. H% Q; H2 L+ d. |4 X4 E, L
7 H) F' |* J' h$ e  ;; give the turtles an initial speed
9 u; A: H6 g' O$ z  ask turtles [ set-car-speed ]  {: m' g3 C8 @# W& m
& [( ^: v, W' F
  reset-ticks
" q7 u  U" B4 f- S" o( f% dend
5 N1 h0 h! O' x( l7 m' j! |
) J- r  H; {2 |) A;; Initialize the global variables to appropriate values/ q) G9 Z" {0 T% W4 N0 O
to setup-globals
' d3 i0 y9 x0 J/ f; i  set current-light nobody ;; just for now, since there are no lights yet
5 {, q9 _8 V5 J! f  set phase 0* s. k; j: H- ]3 V- k$ Z  A- r
  set num-cars-stopped 0
$ Z. P0 e* M: p, J+ T8 D  set grid-x-inc world-width / grid-size-x2 I) A0 J8 Z7 G7 x. h7 Q3 r' F2 ^
  set grid-y-inc world-height / grid-size-y
  v' U8 L% v/ g$ F7 s$ w- l, \1 L7 E- d; t- o. H- D& g* O
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
% m7 [, X" Z2 S/ ^  set acceleration 0.099
, E6 W7 N$ V6 r! vend
% |) j6 G; m& n0 G
" R3 G; O2 q6 h2 T5 z9 C. q;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
( Z2 \9 u' q: {& u/ Q;; and initialize the traffic lights to one setting8 w* K  x0 v; J( o$ |
to setup-patches" @' m, q# m" D2 [) z# k  I2 H+ T
  ;; initialize the patch-owned variables and color the patches to a base-color
  O& Z* V/ g6 a  O% R  ask patches
9 a8 K; W  F: O, c3 Z7 e  [
* W' T$ O9 ]' y$ S  i- Y+ o    set intersection? false
8 Q# k( h: i8 a9 k; m& }    set auto? false4 x8 q% {  L, a0 p% T0 D5 ?2 j' i+ [$ `
    set green-light-up? true9 o7 r3 B+ T2 X/ ^* H
    set my-row -1
% t+ U  a' _/ r9 Z% P    set my-column -1
5 P7 ~0 p& e0 X8 x: O    set my-phase -1
  L* Y4 |$ g; ~    set pcolor brown + 3
) w9 [6 z8 u8 k0 a8 [0 F  ]# D- t+ [) d6 G
/ g; L- n+ j7 A! l6 N7 o5 U  C
  ;; initialize the global variables that hold patch agentsets9 v1 M1 @) y" U1 z
  set roads patches with
9 }- I2 Q) B  L, `    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
1 T" j, U( b) W* \    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]* k5 b9 T5 y: u! O9 y8 n
  set intersections roads with8 O$ p$ ?" f' p3 K' }1 ~
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and9 q# y  c% c( h7 R
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
4 R; x2 l) k& r: @$ V$ y& m; h
) H! x5 Y* y7 w  Y! Y. \( ~  ask roads [ set pcolor white ]+ ~# k% }- \$ r2 E7 U' p6 G) N
    setup-intersections! t' a: |$ W4 ]" F# B6 s4 W/ S
end
5 X2 p+ ?0 Y+ Q其中定义道路的句子,如下所示,是什么意思啊?: R+ ~, f. `! p9 [. r6 d
set roads patches with
( y/ p. V) W- M) d) z4 t4 D6 @8 r3 A    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or/ b, ~0 X, @' @+ b( j9 F$ E9 z
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
) B# M) g/ O% p& m: Z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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