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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。0 j8 E+ n6 C( K! x6 s. M" Q; i) ^9 O
netlogo自带的social science--traffic grid这一例子当中,
# ?7 Q% ]: ^/ r" z5 p( eglobals
4 x8 I8 K* r2 q4 ]7 ~[
$ r- v$ N, B+ Y" J- @2 g  grid-x-inc               ;; the amount of patches in between two roads in the x direction% P0 c& J. B: `, i& d9 L
  grid-y-inc               ;; the amount of patches in between two roads in the y direction
) |' ]9 A! L& j  W  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
6 e% V- E5 W3 |                           ;; it is to accelerate or decelerate
' R9 X; d! [' z2 F  phase                    ;; keeps track of the phase, S4 ], o% J: M- Z+ [/ m
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure; G* R3 D/ P" T/ _2 z' U" s3 M
  current-light            ;; the currently selected light
8 \) b- W$ q0 n4 ^2 r5 ?' k3 w* `. n6 z! V) f" ?9 I
  ;; patch agentsets: J. `' l  \. Y# Y, \
  intersections ;; agentset containing the patches that are intersections
' W/ J" G% w8 @  S2 \3 n4 V  roads         ;; agentset containing the patches that are roads) h( a. ?" M8 m  r5 n* Y
]
1 I" L: u3 L4 H9 [6 T& T3 K* a# [2 R2 h) Z% y  d# c
turtles-own
( b/ M* N3 h8 C& y% w% w+ D. i[6 o. Z. u: U# }+ o7 ~  D
  speed     ;; the speed of the turtle6 h0 P3 z9 G+ T2 d( ~# e+ i( B
  up-car?   ;; true if the turtle moves downwards and false if it moves to the right5 ?( V, }% O% f# k2 `3 x2 Y
  wait-time ;; the amount of time since the last time a turtle has moved
2 u0 D& v. Y) o7 {1 V2 o/ M6 r4 h]
5 z$ h8 E% Q$ W2 `' _, I* L$ V' K4 [( r& O) @* q) q/ Z' `- N
patches-own
5 C3 V) k* i# g6 _[
* \& S9 s0 [7 `7 T/ o  l  intersection?   ;; true if the patch is at the intersection of two roads. J$ e9 Y5 d/ m* Z2 r0 y4 e" g2 e
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
/ z1 ^0 `, t, c  b% D% ~' _                  ;; false for a non-intersection patches.
! j3 {5 a8 p" A8 ~4 x9 h9 a5 l' Y8 d  my-row          ;; the row of the intersection counting from the upper left corner of the. I1 Q' c9 v9 ~' L2 W
                  ;; world.  -1 for non-intersection patches.2 g6 t0 `8 A9 T1 N( N4 x4 C6 R
  my-column       ;; the column of the intersection counting from the upper left corner of the
3 o! d' N+ d  \2 e' [                  ;; world.  -1 for non-intersection patches.
5 `) Z: p4 }% \$ Y  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.: R6 s$ s( T! X
  auto?           ;; whether or not this intersection will switch automatically.
# Z$ M% o' s6 Y- O8 g& \3 S                  ;; false for non-intersection patches.& k! V6 `4 }: e* i! b* s" W: T! n
]' N5 l4 @! Y/ r
6 R* ^* p5 y$ }% I+ W. `- j7 G2 ^

$ e- L/ p, J9 {* c9 i, k! o;;;;;;;;;;;;;;;;;;;;;;
# g# B8 E0 i* p;; Setup Procedures ;;3 v: T% F1 n* ^
;;;;;;;;;;;;;;;;;;;;;;
6 k3 ~9 d8 X% v# G- j. T: l. k8 U9 b1 E0 Q- {
;; Initialize the display by giving the global and patch variables initial values.
* {/ y3 j) T0 z6 u: T; [, W& s/ [( D;; Create num-cars of turtles if there are enough road patches for one turtle to+ `4 g# Q, H, G1 D
;; be created per road patch. Set up the plots.0 Q. c) c3 |' k4 A0 v2 Z! D$ v
to setup
' q; O: X7 f6 w, f! i6 K0 z  ca' u" C+ d# ^1 B# b2 f. ?
  setup-globals
9 U# F1 A: L, P- `. q8 G- p) O" i
. `+ t* ~0 u. K& A  ;; First we ask the patches to draw themselves and set up a few variables
" a4 n) {# v2 l  setup-patches
& ^% Z& I! s# p# q% z  make-current one-of intersections
2 f* z. E4 `9 I  label-current0 j0 T7 U) o/ e- u& C

% h* p' w. d; C3 k3 W  set-default-shape turtles "car"
' P! w& v( H0 A! z* P5 |" \/ }8 f) e0 a9 x! D1 j: c
  if (num-cars > count roads)3 k5 b& L; Q+ [6 X3 Y
  [" `; g  j- G. U6 Z6 H
    user-message (word "There are too many cars for the amount of ": P. R- b. e0 [; R
                       "road.  Either increase the amount of roads "+ F1 {; M: f5 _
                       "by increasing the GRID-SIZE-X or "
5 V2 B. B2 r9 R+ d5 x                       "GRID-SIZE-Y sliders, or decrease the "1 a/ c0 X) y/ H& N6 h
                       "number of cars by lowering the NUMBER slider.\n"
1 I) D8 R( s8 r; @                       "The setup has stopped.")
: n& @* ~6 F4 v3 ?$ k1 p    stop9 G2 |8 ^  O$ d0 R, y
  ]
2 r6 Q( @% z4 L3 |4 S8 B
! D# F# u5 D6 w# \6 Q( P  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color+ F; O: o( n% i. ]
  crt num-cars
! i" [7 H/ ^9 `8 w# ~2 C0 D  [( s- C0 C1 H4 K
    setup-cars6 A) F% s( Y& y- V  b. x
    set-car-color
- A1 b$ i9 X7 S6 v+ s$ c, z. R    record-data9 p4 C: a  c3 I$ E9 [/ H5 f- `/ j
  ]
' u" J$ d! g: ~8 f8 w0 o8 X4 F- K  y2 g
  ;; give the turtles an initial speed7 c( ]  {# ~# p! b; x
  ask turtles [ set-car-speed ]9 @4 |, v) d7 y( P
4 s2 E1 S. O) I- O: ]
  reset-ticks
+ d. U- \, m" c  _% R  Fend
! ~/ V# n+ R# g/ T, V$ ^1 Y/ w$ n! R/ F) Q+ Z# Y  P1 g, x
;; Initialize the global variables to appropriate values
% f2 K$ |1 ^) Uto setup-globals
5 F2 }! V5 Q9 @( U. [' O  set current-light nobody ;; just for now, since there are no lights yet- C! y) {4 j" h/ ?9 e7 H
  set phase 0
7 _) |) T# P* {1 w0 k* Y; B$ Q* b  set num-cars-stopped 0" Y& I1 s! O* i# X  E& {
  set grid-x-inc world-width / grid-size-x
* k  y* K: }/ J+ d; e# `  set grid-y-inc world-height / grid-size-y, O5 W9 l# z0 e$ D" e
# m- a, T& k' R/ h
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary+ ~1 F* o* r6 a8 V0 n* Z
  set acceleration 0.0993 b0 i# b! i" |0 T
end
' ?6 w* i5 _6 w& [9 n% x
: @$ R- @5 r' T! l2 @; M* t;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
0 `& f) |! E3 L/ l. I% x2 x8 Z;; and initialize the traffic lights to one setting
* q$ d" L3 E! Mto setup-patches# ^3 i4 C! h/ l& u7 w" |
  ;; initialize the patch-owned variables and color the patches to a base-color0 n( _6 }  I% E4 W+ ~6 p
  ask patches
: o" ~' f+ m3 n- n$ c; f  [
& R2 Z( [/ [1 X+ y, @1 U: q    set intersection? false1 h* _+ }* o" {. f
    set auto? false
: v9 G5 C( n% C  I, C, ~- ?, Q    set green-light-up? true
  T" J2 L" g% a2 z    set my-row -1
- k- x4 @8 w* R* x% D    set my-column -1" o+ `2 c! c" z, L) D
    set my-phase -1
$ q8 d2 R+ _' _6 |& v1 m+ {    set pcolor brown + 3* ?0 M- @; [5 m! J1 |2 Y
  ]
+ O( a3 _/ o! b7 `( A
7 U4 s0 \  _: s2 s6 [  u  ;; initialize the global variables that hold patch agentsets% t6 c6 U- I0 I  S  Y
  set roads patches with
! P) ]$ f% j0 j8 t& ?    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
) r& |; E6 y' p) j; f3 m    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]. h% U4 {$ V9 b% n' n, V
  set intersections roads with
) o* K5 R8 B, O8 i    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
5 V. j+ c- Y; g. B$ s    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
3 r7 F2 y* Y: D$ G) \) a  l' e
5 l. J0 b4 N2 t5 C, F4 K7 Q8 l  ask roads [ set pcolor white ]
9 t3 e  u* t7 L    setup-intersections! }- R- y) l- O$ N
end% a: f8 O- R* q. h
其中定义道路的句子,如下所示,是什么意思啊?9 C  F# c. f2 |1 l# b; G- s
set roads patches with9 _  Q& _* O' i& v! |. k
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or% m/ a+ b9 W/ |) f# Q) b
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]$ _3 N, l& l7 l# p) Q* c
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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