🐢 B4XTurtle - Library for teachers and parents

inakigarm · Apr 28, 2020

Is it "normal" that if turtle draws outside canva's pane the results are like that?
If the radius is high, the turtle continue to draw from side's canvas (It seems that should be better not to draw outside the pane and not continue from the other sides of the canvas)

Erel · Apr 28, 2020

Good job Ilan!

Erel · Apr 28, 2020

inakigarm said:
Is it "normal" that if turtle draws outside canva's pane the results are like that?

Yes. The drawing continues on the other side. This is how classic Logo works.

Sandman · Apr 28, 2020

ilan said:
i am sure there is a better and shorter way

There might be a shorter way, but I can't see anything wrong with solving it like this. Looks good to me!

LucaMs · Apr 28, 2020

ilan said:
For i = 1 To 360 Turtle.MoveForward(((r*2)*cPI)/360).TurnLeft(1) Next

Why calculate 360 times the "fixed" value: (r*2)/cPI/360?

LucaMs · Apr 28, 2020

ilan said:
i am sure there is a better and shorter way

I did it differently because I hoped to be able to make a continuous track, but I don't think it's possible; for this purpose I used the PushState and PopState methods, which allow that "effect".

I hope I haven't written too incomprehensible and illogical things ... I'm sleepy ?

LucaMs · Apr 28, 2020

Just Circle:

B4X:

Public Const CLOCKWISE As Int = 1
Public Const COUNTERCLOCKWISE As Int = 2

B4X:

' Wise - pass one of the two contants provided:
' CLOCKWISE or COUNTERCLOCKWISE.
Sub Circle (x As Float, y As Float, r As Float, Wise As Int)
    Turtle.SetX(x).SetY(y - r / 2)
   
    If Wise = CLOCKWISE Then
        Turtle.SetAngle(0)
    Else
        Turtle.SetAngle(180)
    End If
   
    Dim v As Float = (r * cPI) / 360
    For i = 1 To 360
        If Wise = CLOCKWISE Then
            Turtle.MoveForward(v).TurnRight(1)
        Else
            Turtle.MoveForward(v).TurnRight(-1)
        End If
    Next
End Sub

LucaMs · Apr 28, 2020

LucaMs said:
Just Circle:

Erel · Apr 28, 2020

LucaMs said:
Why calculate 360 times the "fixed" value: (r*2)/cPI/360?

This is a preoptimization which is not relevant unless you plan to draw millions of circles per second (in rabbit mode).

LucaMs · Apr 28, 2020

Erel said:
This is a preoptimization which is not relevant unless you plan to draw millions of circles per second (in rabbit mode).

I know (and I could see it) but it is just a good practice avoid "logical errors".

ilan · Apr 28, 2020

LucaMs said:
Why calculate 360 times the "fixed" value: (r*2)/cPI/360?

i also used a variable but when i posted the code i wanted it to be as short as possible. you know that's the "key" in a challenge
in real life i would use a variable and do the calculation only once.

LucaMs said:

Just Circle:

B4X:

Public Const CLOCKWISE As Int = 1
Public Const COUNTERCLOCKWISE As Int = 2

B4X:

' Wise - pass one of the two contants provided:
' CLOCKWISE or COUNTERCLOCKWISE.
Sub Circle (x As Float, y As Float, r As Float, Wise As Int)
    Turtle.SetX(x).SetY(y - r / 2)
 
    If Wise = CLOCKWISE Then
        Turtle.SetAngle(0)
    Else
        Turtle.SetAngle(180)
    End If
 
    Dim v As Float = (r * cPI) / 360
    For i = 1 To 360
        If Wise = CLOCKWISE Then
            Turtle.MoveForward(v).TurnRight(1)
        Else
            Turtle.MoveForward(v).TurnRight(-1)
        End If
    Next
End Sub

code is to LONG to do only a circle ?

LucaMs · Apr 28, 2020

I don't like "compact code", I much prefer code that is easy to read, debug, maintain and upgrade.

LucaMs · Apr 28, 2020

ilan said:
code is to LONG to do only a circle

That code, as you see, places the turtle in a precise position with respect to the center and allows you to draw both clockwise and counterclockwise. Of course, if you remove the empty lines, it may seem shorter ?

ilan · Apr 28, 2020

what about drawing a "fish" (our turtle) swimming on a wave?

B4X:

Sub drawwave(r As Float)
    ...
End Sub

LucaMs · Apr 28, 2020

wave height and length.

ilan · Apr 28, 2020

LucaMs said:
wave height and length.

use r instead

B4X:

drawwave(60)

ilan · Apr 28, 2020

no one with a solution?

LucaMs · Apr 28, 2020

ilan said:
no one with a solution?

I'm too sleepy. I would say two loops, the external one with a step which is then the limit of the internal loop.
Something like:

B4X:

For i = 0 to AAA Step BBB
    For J = i to i + BBB - 1 ' <--- for the wave, sine curve

ilan · Apr 28, 2020

LucaMs said:
I'm too sleepy. I would say two loops, the external one with a step which is then the limit of the internal loop.
Something like:

B4X:

For i = 0 to AAA Step BBB For J = i to i + BBB - 1

actually its very simple:

B4X:

Sub drawwave(r As Float)
    Dim oppositedirection As Boolean = True
    Turtle.TurnRight(30)
    For i = 1 To 2000
        If oppositedirection Then Turtle.MoveForward(((r*2)*cPI)/360).TurnLeft(1) Else Turtle.MoveForward(((r*2)*cPI)/360).TurnRight(1)
        If i Mod 60 = 0 Then oppositedirection = Not(oppositedirection)
    Next
End Sub

LucaMs · Apr 28, 2020

ilan said:
(r*2)*cPI)/360

Again ?

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