在看例子时有几个问题看不懂

yanyanxihua

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。
netlogo自带的social science--traffic grid这一例子当中，
globals
[
- @* p" V+ M2 M0 F  grid-x-inc               ;; the amount of patches in between two roads in the x direction
1 Z+ @: y4 R+ b! o# i0 y% o  grid-y-inc               ;; the amount of patches in between two roads in the y direction
  acceleration             ;; the constant that controls how much a car speeds up or slows down by if
3 ?6 g# Y. A+ h: {                           ;; it is to accelerate or decelerate
  phase                    ;; keeps track of the phase
  num-cars-stopped         ;; the number of cars that are stopped during a single pass thru the go procedure
  current-light            ;; the currently selected light

# a. s5 C/ v$ D- K9 D# ]  ;; patch agentsets
4 o0 {1 u9 R( j! R$ K  intersections ;; agentset containing the patches that are intersections
  b6 ^$ I& r+ \$ K" I  roads         ;; agentset containing the patches that are roads
]

! h. B: s9 S5 B: c' F- qturtles-own
[
( C" u. Z2 T  f  U- K  speed     ;; the speed of the turtle
, P( J2 U5 @+ E% n5 @9 ?0 D  \  up-car?   ;; true if the turtle moves downwards and false if it moves to the right
% m0 p/ |) r0 a* N% g7 b/ a  wait-time ;; the amount of time since the last time a turtle has moved
]

$ e6 F: A# K1 G& {9 [1 P8 Zpatches-own
[
; c2 c2 M- g$ V: R5 a/ z  intersection?   ;; true if the patch is at the intersection of two roads
6 A0 v* S+ L8 o+ ]- d6 g) E' G  green-light-up? ;; true if the green light is above the intersection.  otherwise, false.
                  ;; false for a non-intersection patches.
  my-row          ;; the row of the intersection counting from the upper left corner of the
  b, d( s5 C  G& x                  ;; world.  -1 for non-intersection patches.
7 |' u. x7 l: Z6 x* m  my-column       ;; the column of the intersection counting from the upper left corner of the
                  ;; world.  -1 for non-intersection patches.
2 ?2 ?( H8 N! g) `; a% |% z  my-phase        ;; the phase for the intersection.  -1 for non-intersection patches.
  auto?           ;; whether or not this intersection will switch automatically.
                  ;; false for non-intersection patches.
]


) D2 M3 J. N- _  F7 _  H;;;;;;;;;;;;;;;;;;;;;;
;; Setup Procedures ;;
3 V9 B# f2 w6 W9 X8 R;;;;;;;;;;;;;;;;;;;;;;

;; Initialize the display by giving the global and patch variables initial values.
;; Create num-cars of turtles if there are enough road patches for one turtle to
! a) H1 l$ H5 U;; be created per road patch. Set up the plots.
to setup
7 D* ^/ j0 G+ C& G  ca
  setup-globals
( v' @0 p8 j" t/ U3 \& K
  ;; First we ask the patches to draw themselves and set up a few variables
/ ^$ q5 U) X- H( o, w# N2 k  setup-patches
  make-current one-of intersections
  label-current
$ M: ^9 L5 r' p: E/ v+ ^4 O; l
  set-default-shape turtles "car"
/ R) e. i, X3 Q9 l1 y* D& J$ h
  if (num-cars > count roads)
+ M- G/ {# B6 t' e; ]3 f  [
3 |# ?2 Q3 }) E) X  [8 J( s    user-message (word "There are too many cars for the amount of "
% V' s3 \3 \2 k. }- X$ u                       "road.  Either increase the amount of roads "
5 v& q& }3 H; _4 @                       "by increasing the GRID-SIZE-X or "
7 _' R6 F' ~/ ~( e6 r3 x: r                       "GRID-SIZE-Y sliders, or decrease the "
                       "number of cars by lowering the NUMBER slider.\n"
9 u6 c4 r6 Z( ]$ n4 j  s                       "The setup has stopped.")
/ z8 i2 n, D4 O* k' F/ S    stop
  ]

) J7 M& U" C. h6 \1 s) d  ;; Now create the turtles and have each created turtle call the functions setup-cars and set-car-color
  crt num-cars
  [
' J) y) t+ ~- N    setup-cars
# q8 \5 ], f0 w4 l    set-car-color
    record-data
  ]
! y0 b" d& i! k0 ~2 [' N& y
( v, E0 ^/ [) |1 c( c  ;; give the turtles an initial speed
  ask turtles [ set-car-speed ]
9 q4 E2 o; |+ v, [4 @. I
  reset-ticks
end

;; Initialize the global variables to appropriate values
to setup-globals
  set current-light nobody ;; just for now, since there are no lights yet
  set phase 0
% u: B3 v0 o$ E; s4 V  set num-cars-stopped 0
  set grid-x-inc world-width / grid-size-x
  set grid-y-inc world-height / grid-size-y
/ W7 R* O; o4 e8 M8 t$ X
  ;; don't make acceleration 0.1 since we could get a rounding error and end up on a patch boundary
  set acceleration 0.099
end
  G# Q5 J9 ~; r% u1 o
' S( V- N: R8 I+ I$ |7 T. F;; Make the patches have appropriate colors, set up the roads and intersections agentsets,
;; and initialize the traffic lights to one setting
to setup-patches
' b* m+ l0 S8 z  q. G$ l3 \  ;; initialize the patch-owned variables and color the patches to a base-color
' {8 z% `4 |$ u. s) C$ L  ask patches
6 F$ w/ h) R) \) ?7 B# o  [
    set intersection? false
    set auto? false
    set green-light-up? true
: o# _" Z) l* e; g6 `- ?    set my-row -1
    set my-column -1
; G5 h* t7 Q( B+ S1 @    set my-phase -1
    set pcolor brown + 3
  ]

  ;; initialize the global variables that hold patch agentsets
  set roads patches with
    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
  set intersections roads with
( n# o' U0 a* H+ t( K    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) and
! Q" `: |& K6 t% }  n    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]

0 x  ~# Z8 j1 f0 T: C  p  ask roads [ set pcolor white ]
    setup-intersections
end
其中定义道路的句子，如下所示，是什么意思啊？
- T1 d6 A- D4 }& e, z! Z set roads patches with
- I0 O5 s: l9 W) R$ \* K$ i% w    [(floor((pxcor + max-pxcor - floor(grid-x-inc - 1)) mod grid-x-inc) = 0) or
: O0 p! H; a, F4 @: U    (floor((pycor + max-pycor) mod grid-y-inc) = 0)]
( m& k  t4 a+ ]* g- 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？