Writing with the Turtle, part 3

Here below is code similar to the code of part 2 but extended to include sequences for every capital letter A-Z, every digit 0-9, as well as the space and hyphen characters. This program waits for you to type a character which the turtle then draws for you. When the turtle has finished drawing (and there is code to check that it really has finished) then you can try another character. The way the program detects that a key has been pressed while the graphics window is active is by using this command:

GraphicsWindow.TextInput = OnTextInput

That code tells the program that if a key is pressed then the subprogram 'OnTextInput' should be called. The character corresponding to the pressed key is stored in GraphicsWindow.LastText ready to be used by the program.

If you don't like the way I've designed certain characters then feel free to modify the code - it's a great way to learn! Note that the sequences below do not include the '10' pair that you have seen at the end of every sequence previously - this pair corresponds to the space between characters which is not relevant to this program.

GraphicsWindow.Width=500

GraphicsWindow.Height=500

GraphicsWindow.PenWidth=4

Turtle.Speed=7

Turtle.PenUp()

GraphicsWindow.penColor="yellow"

For y=50 To 450 Step 200 'draw horizontal grid lines

GraphicsWindow.DrawLine(150,y,350,y)

EndFor

For x=150 To 350 Step 100 'draw vertical grid lines

GraphicsWindow.DrawLine(x,50,x,450)

EndFor

GraphicsWindow.TextInput = OnTextInput 'Call the OnTextInput

'subprogram if a key press is detected

GraphicsWindow.Title="Type a character"

GraphicsWindow.penColor="black"

busy="False"

Sub OntextInput

If busy="False" then

busy="True" 'Don't allow another drawing

'to begin until this one is complete

For i = 1 To 10000 'bug workaround - see below

Shapes.Remove("_turtleLine"+i)

EndFor

char = GraphicsWindow.LastText ' get the character entered

Turtle.x=150

Turtle.y=450

Turtle.Angle=90 'point right

sequence[0]= "1P Qq 20 Qr 20 Qq 0p 10"

sequence[1]= "0A 30 0c 0P cc 0a 4p 0A 5P 2p"

sequence[2]= "0A 3P qs Qq 1A 2p"

sequence[3]= "0P 10 Qr QR 5p 0f fF"

sequence[4]= "1A 0P 2p 2A 0H 0P gG 0A 2p 0a 1A"

sequence[5]= "0P 10 Qr 1a 2a 2p 0a 4A"

sequence[6]= "0N mM 0P Qr 20 Qs 1p 0A 0C dC"

sequence[7]= "1K 0P jJ 0A 2p 0A 0E fF"

sequence[8]= "1P Qr qt Qr 0p 10"

sequence[9]= "0P 10 Qq 20 Qs 1p 0a 2A"

sequence["A"]= "0A 0P 2a 2p 6F 0P ef 0f ee 2p 0A"

sequence["B"]= "0P 10 Qr 1p 5P QR 5a 4p 0A 20"

sequence["C"]= "0N mM 0P Qr 20 Qr 0p 5a"

sequence["D"]= "0P 10 Qq 20 Qq 1A 4p 0A 20"

sequence["E"]= "0A 2a 0P 1p 0F eE 0A 0P 2A 4A 2p"

sequence["F"]= "0A 2a 0P 1F 0p eE 0A 0P 2A 4p 0A 20"

sequence["G"]= "0F ef 0P 1a 10 qr 20 qr 0p 3A"

sequence["H"]= "0A 2a 0P 2p 0C DC 0P 4p 0a 2a 0P 4p 0A"

sequence["I"]= "0P 2p 0A 4A 0P 2p 5A 0P 4p 0A 10"

sequence["J"]= "0A 4a 0P 2a 30 qr 0p 0a 0e eE"

sequence["K"]= "0A 0P 4p 0a 2C 0P Da dp 0C"

sequence["L"]= "0A 4P 8a 2p"

sequence["M"]= "0A 0P 4a 0f ee 0e EE 4p 0A"

sequence["N"]= "0A 0P 4E Fe 4p 8a"

sequence["O"]= "1P Qq 20 Qr 20 Qq 0p 10"

sequence["P"]= "0A 0P 4a 10 qr 1p 0A 0C dC"

sequence["Q"]= "1P Qq 20 Qr 20 Qq 0p 0A 1a 0c 0P cp 0C"

sequence["R"]= "0A 0P 4a 10 qr 1A 0C dp 0C"

sequence["S"]= "0a 5P Qs qs 0p 3A"

sequence["T"]= "0A 4a 0P 2p 5a 0P 4p 0A 10"

sequence["U"]= "0a 8P 30 Qr 3p 7P 5p 0a"

sequence["V"]= "0A 4J 0P Jj 0j jp 0J 8a"

sequence["W"]= "0A 4P 8e eE 0E Ee 4p 8a"

sequence["X"]= "0F 0P fp 0f 6f 0P fp 0F"

sequence["Y"]= "1A 0P 2E ep Ee 0e 0P ep 0E 8a"

sequence["Z"]= "0A 4a 0P 2F Ff 2p"

sequence[" "]= "20" 'space

sequence["-"]= "0A 2a 0P 2p 0a 2A" 'hyphen

For n=1 to (1+Text.GetLength(sequence[char]))/3

movechar=text.GetSubText(sequence[char],n*3-2,1)

unicode=Text.GetCharacterCode(movechar)

If unicode>64 And unicode<91 Then 'capital letter

movesign=-1

movechar=text.ConvertToLowerCase(movechar)

Else

movesign=1

EndIf

turnchar=text.GetSubText(sequence[char],n*3-1,1)

turn_unicode=Text.GetCharacterCode(turnchar)

If turn_unicode>64 And turn_unicode<91 Then 'capital letter

turnsign=-1

turnchar=text.ConvertToLowerCase(turnchar)

Else

turnsign=1

EndIf

If movechar="0" Then

' do nothing

ElseIf movechar="1" Then

Turtle.Move(100)

ElseIf movechar="2" Then

Turtle.Move(200)

ElseIf movechar="3" Then

Turtle.Move(300)

ElseIf movechar="4" Then

Turtle.Move(400)

ElseIf movechar="5" Then

Turtle.Move(-100)

ElseIf movechar="6" Then

Turtle.Move(-200)

ElseIf movechar="7" Then

Turtle.Move(-300)

ElseIf movechar="8" Then

Turtle.Move(-400)

ElseIf movechar="9" Then

Turtle.Move(25)

ElseIf movechar="c" Then

Turtle.Move(movesign*141.4)

'Motor.Move(ports,10,141.4*s,1)

ElseIf movechar="d" Then

Turtle.Move(movesign*282.8)

'Motor.Move(ports,10,282.8*s,1)

ElseIf movechar="e" Then

Turtle.Move(movesign*223.6)

ElseIf movechar="f" Then

Turtle.Move(movesign*447.2)

ElseIf movechar="g" Then

Turtle.Move(movesign*316.2)

ElseIf movechar="j" Then 'sqr(5)

Turtle.Move(movesign*412.3)

ElseIf movechar="m" Then

Turtle.Move(movesign*360.6)

ElseIf movechar="q" Then 'draw arc

If turnchar="q" Then

imax=45 '90° in 45 steps of 2° each

ElseIf turnchar="r" Then

imax=90 '180°

ElseIf turnchar="s" Then

imax=135 '270°

ElseIf turnchar="t" Then

imax=180 '360°

EndIf

For i=1 to imax

Turtle.Move(turnsign*3.49) ' 2*pi*100/(4*45) =3.49

Turtle.Turn(movesign*2)

EndFor

EndIf

If turnchar="0" Then

' do nothing

ElseIf turnchar="a" Then

Turtle.Turn(turnsign*90)

ElseIf turnchar="b" Then

Turtle.Turn(turnsign*180)

ElseIf turnchar="c" Then

Turtle.Turn(turnsign*45)

ElseIf turnchar="e" Then

Turtle.Turn(turnsign*26.565)

ElseIf turnchar="f" Then

Turtle.Turn(turnsign*63.434)

ElseIf turnchar="g" Then

Turtle.Turn(turnsign*18.435)

ElseIf turnchar="h" Then

Turtle.Turn(turnsign*71.565)

ElseIf turnchar="j" Then

Turtle.Turn(turnsign*14.036)

ElseIf turnchar="k" Then

Turtle.Turn(turnsign*75.963)

ElseIf turnchar="m" Then

Turtle.Turn(turnsign*33.69)

ElseIf turnchar="n" Then

Turtle.Turn(turnsign*56.31)

ElseIf turnchar="p" Then

If turnsign=1 Then

Turtle.PenUp()

Else

Turtle.PenDown()

EndIf

EndFor

busy="False"

EndIf

EndSub

Note that Small Basic has a bug in which if your use the command GraphicsWindow.Clear() then it becomes impossible to show the turtle again. Since in this program I wanted to allow you, the user, to have turtle draw characters again and again, clearing the previous drawing before starting the new one, I had to use the 'workaround code' above (in bold) which deletes all the previous lines left by the turtle, each of which is actually a 'shape'.

You may notice when you run the program that some characters (such as 'B' are not quite drawn perfectly). This is because of the rounding errors that often occur when the distances and angles are given, and also because of the need to draw the arcs as a set of straight lines since Small Basic has no arc-drawing function.

These drawing errors will become a very big issue when we move from the Small Basic graphics window to a real robot, which is the NEXT STEP.