%!PS-Adobe-3.0 EPSF-3.0
%%Title: L-System
%%Creator: (me)
%%BoundingBox: 0 0 500 500
%%EndComments
%
% %% BeginProlog ... %% EndProlog are document structuring comments
% to give definitions of new "resources" (operators, fonts, etc.)
%
% %% BeginResource ... %% EndResource encloses a resource
% as a set of operators (procset).
%
%%BeginProlog
%%BeginResource: procset (graphisme tortue) 1.0 0
% --------- definition of operations for turtle graphics
%
% The coordinate system follows the movements and turns of the turtle,
% so that the tourtue is always at the origin with the next rotates
% towards the X axis.
%
% Operations:
% T: move advances the turtle
% T: draw advances the turtle by drawing a line between the start and finish points
% T: turn turns the turtle's nose
/T: move% d T: move -
% advances the turtle by d (number --- positive, negative or 0)
{
0 translate % put the origin at this new position
} def
/T:draw % d T: draw -
% advance the turtle by d drawing a line
{
newpath
0 0 moveto
0 lineto
currentpoint
stroke
translate
} def
/T:turn % angle T: turn -
% turns the turtle's nose by the angle (in degrees)
{
rotate
} def
/T:init % x y angle T: init -
% initial state of the turtle
{
3 1 roll translate
rotate
} def
%%EndResource
%%BeginResource: procset (random rule) 1.0 0
realtime srand % random seed --- during tests, use a fixed value (e.g., 30 rand) if necessary for repeatability
/L: rnd % [op1 op2 ...] L.rnd -
% chooses an operator at random and executes it
% op1, op2 etc are names (start with /)
{
rand % random number between 0 and 2 ^ 31-1
1 index length % length of the array
mod % random number between 0 and len-1
get
cvx % conversion to executable
exec % execute
} def
%%EndResource
% ---------------- BEGIN
/L:d 1.5 def
/L:a 60 def
/L
{
dup 0 eq
{
L:d T:draw
pop
}{
1 sub
dup L
L:a T:turn
dup R
L:a T:turn
L:a T:turn
dup R
L:a neg T:turn
dup L
L:a neg T:turn
L:a neg T:turn
dup L
L
L:a neg T:turn
dup R
L:a T:turn
}ifelse
}def
/R
{
dup 0 eq
{
L:d T:draw
pop
}{
1 sub
L:a neg T:turn
dup L
L:a T:turn
dup R
dup R
L:a T:turn
L:a T:turn
dup R
L:a T:turn
dup L
L:a neg T:turn
L:a neg T:turn
dup L
L:a neg T:turn
R
}ifelse
}def
/omega
{
L
} def
%%EndResource
%%EndProlog
500 500
90
T:init
3
omega
%%EOF
为什么它不起作用？我尝试使用 mac OS 的默认 pdf 查看器运行它，它说它无法将此 eps 文件转换为 pdf（通常可以）。
这段代码分为三部分，第一部分是定义海龟操作的地方。我们希望这个文件允许我们在屏幕上绘制东西。
/T: move% d T: move -
% advances the turtle by d (number --- positive, negative or 0)
{
0 translate % put the origin at this new position
} def
/T:draw % d T: draw -
% advance the turtle by d drawing a line
{
newpath
0 0 moveto
0 lineto
currentpoint
stroke
translate
} def
/T:turn % angle T: turn -
% turns the turtle's nose by the angle (in degrees)
{
rotate
} def
/T:init % x y angle T: init -
% initial state of the turtle
{
3 1 roll translate
rotate
} def
%%EndResource
%%BeginResource: procset (random rule) 1.0 0
realtime srand % random seed --- during tests, use a fixed value (e.g., 30 rand) if necessary for repeatability
/L: rnd % [op1 op2 ...] L.rnd -
% chooses an operator at random and executes it
% op1, op2 etc are names (start with /)
{
rand % random number between 0 and 2 ^ 31-1
1 index length % length of the array
mod % random number between 0 and len-1
get
cvx % conversion to executable
exec % execute
} def
%%EndResource
该文件的第二部分是我指定要绘制的内容的地方。它基于指定的 L 系统的规则。
/L:d 1.5 def
/L:a 60 def
/L
{
dup 0 eq
{
L:d T:draw
pop
}{
1 sub
dup L
L:a T:turn
dup R
L:a T:turn
L:a T:turn
dup R
L:a neg T:turn
dup L
L:a neg T:turn
L:a neg T:turn
dup L
L
L:a neg T:turn
dup R
L:a T:turn
}ifelse
}def
/R
{
dup 0 eq
{
L:d T:draw
pop
}{
1 sub
L:a neg T:turn
dup L
L:a T:turn
dup R
dup R
L:a T:turn
L:a T:turn
dup R
L:a T:turn
dup L
L:a neg T:turn
L:a neg T:turn
dup L
L:a neg T:turn
R
}ifelse
}def
/omega
{
L
} def
文件的第三部分是我们要求绘制的地方
500 500
90
T:init
3
omega
%%EOF
它通常应该画一个hexamaze。