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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。7 N/ x# i5 [# l' Y; W
netlogo自带的social science--traffic grid这一例子当中,
, o; c0 ~9 l& `" jglobals
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( z$ C" F" x1 }' W  grid-x-inc               ;; the amount of patches in between two roads in the x direction
  z# v; Y4 r: y! O+ x) s: m! j  grid-y-inc               ;; the amount of patches in between two roads in the y direction
4 O. S" f0 A$ R  n  acceleration             ;; the constant that controls how much a car speeds up or slows down by if8 h' C& ?; w6 n9 h7 p! \0 V/ O4 c4 I
                           ;; it is to accelerate or decelerate6 Q0 W  N. o- E
  phase                    ;; keeps track of the phase5 G7 B1 f4 B4 Z
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure2 P3 c- @1 ?" ^# F$ I1 L0 _* r
  current-light            ;; the currently selected light
0 B  E1 x, c7 I; h, v2 f" V& W' [
  @! g4 d9 @5 s, Z2 ]& n  ;; patch agentsets
9 I+ t. f1 n, T- }% t2 E" T. K  intersections ;; agentset containing the patches that are intersections
$ y. Z+ M9 N) T8 |  u  roads         ;; agentset containing the patches that are roads
) \6 d; P$ A3 D) [9 C* w- H]
. k$ X9 S9 X- ^$ F! g, a& \+ [; `( s& ?& r0 ^9 _; U6 \) M( W" i4 \! Z
turtles-own% N3 b( n6 |$ k& s; p
[
! f1 P' X# y/ W$ c  speed     ;; the speed of the turtle
$ u; R) P$ h1 o/ J  up-car?   ;; true if the turtle moves downwards and false if it moves to the right6 U. [3 p& ?4 F( j6 S
  wait-time ;; the amount of time since the last time a turtle has moved
; [9 f: g( I( |3 e; @- F2 p]$ r* @( m* F+ V; l* M
9 s0 {% B, Z+ [- }# l, v/ W, [- ~
patches-own
; G! Q7 n1 m+ \4 `1 D$ G  X[
8 Q$ `' |7 x$ A( P. ], r' Z7 X7 T  intersection?   ;; true if the patch is at the intersection of two roads5 E: |! e. n- C2 Y, {' v2 F
  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.8 b8 c& o3 D  d1 U% @+ w! l
                  ;; false for a non-intersection patches.
$ i; {1 ^3 x7 ?$ H& m  k- B1 |  my-row          ;; the row of the intersection counting from the upper left corner of the
/ R9 Q4 e) z# K: T2 C                  ;; world.  -1 for non-intersection patches.4 L. q1 T- X$ b3 T, S) f# q
  my-column       ;; the column of the intersection counting from the upper left corner of the/ V4 L- |+ ^- t# g" a
                  ;; world.  -1 for non-intersection patches., U5 F5 b' t  v( g4 @+ b' a' @
  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.9 v" M- H- R- j. k8 u
  auto?           ;; whether or not this intersection will switch automatically.
% C3 l/ }; i4 q" a' \                  ;; false for non-intersection patches.
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2 f. [( B5 |) a( U* M) E" z: g3 D+ r5 w- E6 o. ^
;;;;;;;;;;;;;;;;;;;;;;& \; \! T5 D& h- @2 L
;; Setup Procedures ;;
' V0 D- |+ i# ], @* \;;;;;;;;;;;;;;;;;;;;;;
3 f6 b! U- o* M8 [  C2 a" l5 F  P8 |/ k2 M6 K$ m9 |2 a
;; Initialize the display by giving the global and patch variables initial values." y( g) i9 g! I, {, [
;; Create num-cars of turtles if there are enough road patches for one turtle to
9 s- m0 k9 u, N3 S( R- b6 z;; be created per road patch. Set up the plots.
# C7 P. R6 i' h1 O6 [5 Y- qto setup* s" ?+ }8 ]& c' k+ _5 w
  ca5 k+ J- x' O/ P2 s4 K, t7 y2 T
  setup-globals; K- l( D4 _( T/ `
: {9 w, Z5 V4 N. I: S. r6 B
  ;; First we ask the patches to draw themselves and set up a few variables
2 i2 f- }7 q0 X8 B  y  setup-patches% R/ i8 h- s9 Z7 _0 R* v7 A: n1 Z
  make-current one-of intersections9 |& S$ @! ], l( ^# `1 ]" F
  label-current7 _$ N& y- K1 C: H: `' I

" C3 j/ v) z5 Y& D  set-default-shape turtles "car"
% W- r8 @  Y/ j: E( \% q0 Z; {* s( v& ~6 o
  if (num-cars > count roads)
# n# S0 D) L, p: {  [  ]1 u6 x/ U! z1 J  J
    user-message (word "There are too many cars for the amount of "
; A. \, l; L5 C; n+ ~                       "road.  Either increase the amount of roads "
5 ~/ z' e, M% k                       "by increasing the GRID-SIZE-X or "
6 z$ ?9 |0 z" A5 d% A  _                       "GRID-SIZE-Y sliders, or decrease the "
' _/ L$ C9 Q2 u  [) r% m9 z                       "number of cars by lowering the NUMBER slider.\n"
. g0 V! Y/ G: l4 H) g                       "The setup has stopped."), K, l% o: ~# M3 f4 y
    stop! x, u7 p9 V: ]/ i. j& t
  ]# N  U( U9 m: O
! X: X$ Y5 g; T
  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color! d7 G. c* w. ~7 w& m
  crt num-cars
+ c2 Q) l& a3 [$ G) e& F0 t  [
9 r5 a# C, \1 |' n% w    setup-cars. U& y- L1 [5 e1 O
    set-car-color1 a: e( U' H9 D. _( w) O
    record-data
& E+ n9 h* F2 J* Z' G. g  ]
0 o- g3 m6 x! ?5 y8 U, N$ l+ }' A, f1 j$ q% e9 o
  ;; give the turtles an initial speed
$ I/ K4 _3 h, B- G* e+ _  ask turtles [ set-car-speed ]4 z5 p4 k: l+ L$ n
3 L1 [' s, G5 V3 h" E$ W  v  l
  reset-ticks
# J% ?6 h  A5 Gend
6 N' N- |$ l& Z; M" P# x5 N5 C# D; a) e! ~- u. n% w; V) \# b. a
;; Initialize the global variables to appropriate values& [2 o+ c" P3 i1 M2 u% [
to setup-globals
, C+ s9 u) e% z5 A2 B  ~  set current-light nobody ;; just for now, since there are no lights yet
, s8 N0 E% x9 [. B% T. f0 m  set phase 0
- O: j: X4 {2 {+ T2 i& Q  set num-cars-stopped 0! Y: p" k5 Y( p# v
  set grid-x-inc world-width / grid-size-x
: M; a# i. W; |, C6 j3 q  set grid-y-inc world-height / grid-size-y
/ \' c# ?6 e; q( u' a/ K9 e9 @  E! J- \2 o  ?: g
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
! }0 T  F9 V( _$ k' y3 b  set acceleration 0.0990 Y# X6 L, d+ P# T1 ]5 Y
end/ X5 c. N3 v+ R5 `. e$ W: }! X
- j, [/ _* N1 [& X! H% W6 ]
;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
5 I' k5 @( m2 j3 G. F- p/ L. B;; and initialize the traffic lights to one setting
  T3 `! H2 P; J. Q  |3 k& xto setup-patches5 S  o4 V* N, e* N6 D
  ;; initialize the patch-owned variables and color the patches to a base-color
1 [' v+ {) ]2 Q: u5 U  ask patches/ ~" p# e  d8 u( F+ \
  [9 R9 y; }8 C: T5 q3 t" u
    set intersection? false
5 r. u, l; A9 P- v    set auto? false
9 r; w1 L6 v+ o. @2 Z    set green-light-up? true
1 b3 K1 P, n$ [6 D( A" E    set my-row -1  c- u% M! K' M# [
    set my-column -1! f* M; a$ r; ?" U
    set my-phase -1
1 t, v6 K" V8 @1 T( \    set pcolor brown + 3
. _% I8 \0 |( A3 o3 E4 y. z7 ?2 w  ]  W/ S! R  a/ s

3 u+ O4 P+ q9 E  ;; initialize the global variables that hold patch agentsets
( T8 z' s' J9 ~9 K( W# i7 ^- ^  set roads patches with9 T" _) h' Z) ?7 }# m9 x" }
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
# |0 i/ V# H% [6 Y: I, o    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]) t' B; w2 J' v. s) R8 z
  set intersections roads with
* h0 q& N: h. F" A/ @3 i( \- j) E    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
7 N* |! S+ z/ n    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
8 P" f; X/ q: x
" D+ w" L. Q+ \% @, e9 J9 X" G  ask roads [ set pcolor white ]
1 v% d" Z' `' d! d7 v6 s. w8 @/ X    setup-intersections
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其中定义道路的句子,如下所示,是什么意思啊?* K# y: l) k/ u% K8 `1 Z& O" z
set roads patches with! J  S" j7 ^- d: m
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
& H9 U& O! L- _2 y2 R! p% U    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]* G+ y" X- \; z1 t# k9 Y. }
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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