Turtle Graphics on Basic

Turtle graphics is the special drawing functions
it prepared for the LOGO language.
It was used for artificial intelligence and educational use.

The cursor like a turtle on the screen,
advance and rotational directions are given,
and the orbit will draw a pattern.

In the turtle graphics realized by a program of 'Basic',
plural tortoises can be moved at the same time by multi-turtle.

Usage example:

forward 80
right 30

80 move forward and rotate 30 degrees on the right.

It can be used from both command and program list.

File: "turtle.bas"
load "http://androidbasic.ninja-web.net/sp/turtle.bas"
Version 2013/07/04 or later is required

Command list
The abbreviated form of two characters(Notation[ ]) is usable, too.

[fd] forward n - n Move forward.
[bk] back n - n Move back.
[rt] right n - Right turn n.
[lt] left n - Left turn n.
[wt] wait n - It stop between n.
[pd] pendown - Pen is lowered.
[pu] penup - Pen is raised. The orbital trace isn't drawn.
[rp] repeat n [ ] - The inside of brackets is repeated n times and performed.
       Multiple structure is possible.
[cs] cls - Clear screen.
[tc] color n - Color n is chosen.(0~15). Same as Basic's coloration-col(n).
[pn] pen n - In multiple cursors, No.n cursor is chosen.
[ps] pos x y - It move to coordinates(x, y). Cann't change by inside of loop.
[mv] move x y - Only x and y move from current position.
[ag] angle n - It set to angle n.
[sp] speed n - It set to speed n. (1~10). larger-faster(default:10)

Variable
It can be used from @0 to @255.
@v n    The value of formula n is assigned to the variable No.v.

Label & Jump
*label    To show a label name in the alphabet after '*'.
[go] goto label    To jump to the position of specified label.

Conditional branch
if n    if the formula n is except '0', the next command is executed.
        if it is '0', it will skip.

About the value of formula.
The parameter can use the same formula & functions as 'Basic'.
Surplus-'mod', so it need a blank for right and left,
it substitute with '%'.
Variable '@v' can also be used into a formula.

Three functions for exclusive use of TG are usable, too.
posx(n)    To get the coordinate X of pen n.
posy(n)    To get the coordinate Y of pen n.
angle(n)    To get the angle of pen n.

The command only for direct
[ld] load file    File is loaded and Executed.
       It isn't necessary to enclose the file name by "".
[md] mode n    Drawing mode change.
0: It draw with the cursor move animation.
1: It draw in straight without animation.

The coordinate origin(0,0) is center of screen,
the right and upper is Plus, the left and under is Minus.

Upper direction is angle of 0 degrees,
It is clockwise and grow big.(0~359)

Usage example:

Variable
@1 100 @2 posx(2) @1 sqr(@1+@2)
@1=100, @2=pen2:x, @1=Square root (@1+@2)

Label
fd 20 *point1 rt 30 fd 40 go point1
forward20, right30, forward40, and goback to front of rt 30.

Branch
if angle(1)>180 lt 2 fd 10
if angle:pen1 larger than 180, left turn2 and forward10.
if not, skip leftturn and next command-forward10.

Multi-turtle Initial pen is No.1, and coordinates start in (0, 0).
tc 1 rt 90 fd 100 pn 2 tc 2 lt 90 sd 5 fd 100
Blue line run to the right, Red line run to the left at speed of half.

The pen can be simultaneously used to a maximum of 16.
When a value in (pen & color) is protruded more than the maximum,
it is reduced to the surplus value automatically.

The commands can be described to a text file and can also be executed from the 'load' command.
It divide by space, between commands, between parameters.

e.g.
The program of star and polygon. (page top)

Execute by 'load tg0.lgo'
file " tg0.lgo"
pn 1 tc 10 mv 0 180 ag 162 rp 5[fd 352 rt 144]
pn 2 tc 9 mv -193 80 ag 45 rp 8[fd 160 rt 45]

It can also edit and save by the editor of Basic for Android.
When line number is attached, it is removed and loaded.

10 pn 1 tc 10 mv 0 180 ag 162 rp 5[fd 352 rt 144]
20 pn 2 tc 9 mv -193 80 ag 45 rp 8[fd 160 rt 45]

When carrying out recursive processing,
it writes in directly among 100~999 lines of "turtle.bas."
The user function 'func endfunc' is used.
It is a portion of 100~250 lines of the next program.
Since line40 have 'input' for a command input, it must be removed by '(rem).
The portion of ' f=tgcom("left 60") ' is the function which send the command of a turtle.
It doesn't proceed to the next command until drawing command finishes.
When use variable of 'Basic' directly; like ' f=tgcom("forward "+str$(ln)) ',
it connect with command-string using a function 'str$()'.
It can setup drawing-mode by line30. (What requires time is set to mode=1)

File [ tg01.bas ]

10 'Turtle Graphics 1.00
20 gosub turtle: :f=tgini()
30d$="":mode=1
40 'if d$="" then input d$:f=tgcom(d$):goto 40
50 '
100 f=tgcom("angle 90 move -180 -40 tc 9")
110 f=koch(360)
120 '
130 func koch(ln)
140 if ln>4 then
150 f=koch(ln/3)
160 f=tgcom("left 60")
170 f=koch(ln/3)
180 f=tgcom("right 120")
190 f=koch(ln/3)
200 f=tgcom("left 60")
210 f=koch(ln/3)
220 else
230 f=tgcom("forward "+str$(ln))
240 endif
250 endfunc
1000 '
1010 end
1020 turtle:
1030cls3:d0=0:tpen=1:f2=0:tmax=0:iflg=0:cnt=0:mode=0
1040 dim tx(16),ty(16),ta(16),tp(16),loopc(16,16),loopp(16,16)
1050 dim tmx(16),tmy(16),tc(16),taa(16),tac(16),lplv(16)
1060 ........

Sample
File [ tg04.bas ]
Load turtle.bas and run, and enter [ load  tg04.bas ] then drawn.

rp 4096[@2 @2+1 @1 @1+@2 @3 @1/1000 @1 (@3-int(@3))*1000 @4 @4+1 tc @4 fd int(@3) rt 1]

File [ tg06.bas ]
Load turtle.bas and run, and enter [ load  tg06.bas ] then drawn.

tc 5 @2 1 mv -50 -50 rp 30[@2 @2+1 tc @2 rp 3[fd 100+@1*6 rt 91]@1 @1+1]

File [ tg02.bas ]

30d$="":mode=1
40 'if d$="" then input d$:f=tgcom(d$):goto 40
50 '
100 r=0.6666666666666666
110 ang=20
120 ln2=2
130 f=tgcom("move 0 -160 tc 12")
140 '
150 f=branch(100)
160 '
170 func branch(ln)
180 if ln<=ln2 then endfunc
190 f=tgcom("forward "+str$(ln))
200 f=tgcom("left "+str$(ang))
210 f=branch(r*ln)
220 f=tgcom("right "+str$(2*ang))
230 f=branch(r*ln)
240 f=tgcom("left "+str$(ang))
250 f=tgcom("penup back "+str$(ln)+" pendown")
260 endfunc

File [ tg03.bas ]

30d$="":mode=1
40 'if d$="" then input d$:f=tgcom(d$):goto 40
50 '
100 f=tgcom("angle 90 move -180 -80 tc 14")
110 f=stitch(360)
120 '
130 func stitch(ln)
140 if ln>4 then
150 f=stitch(ln/3)
160 f=tgcom("left 90")
170 f=stitch(ln/3)
180 f=tgcom("right 90")
190 f=stitch(ln/3)
200 f=tgcom("right 90")
210 f=stitch(ln/3)
220 f=tgcom("left 90")
230 f=stitch(ln/3)
240 else
250 f=tgcom("forward "+str$(ln))
260 endif
270 endfunc

File [ tg06.bas ]
Load turtle.bas and run, and enter [ load  tg06.bas ] then drawn.

rp 36 [rp 34 [fd 12 rt 10] rt 90 @1 @1+1 @2 @1%14+1 tc @2]

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