Logo - Turtle World
Logo has a number of other additional drawing commands, some of these are given below.
- home
- cleartext or ct
- label
- setxy
The label command takes a single word as a quoted string (e.g. “a_string”) or a list of words in [ ] brackets without quotation (e.g. [a string of letters]) and prints them on the graphics window at the location of the turtle. Let us consider the following code.
The setxy command takes two arguments, treats the first as the value of the abscissa (horizontal axis) and the second as a value of the ordinate (vertical axis). It places the turtle at these coordinates, possibly leaving ink while reaching these coordinates. In the following three figures, we have shown how the setxy command can be used.
The cleartext command, abbreviated ct, clears the text region of the command window.
Exercise
Following is an exercise to check your aptitude on what you have learned so far in this chapter.
What kind of figure does the following command sequence produce?
cs pu setxy -60 60 pd home rt 45 fd 85 lt 135 fd 120
Interpret these commands as you read them from left to right. Try it to find out the result.
Following is a table of command summary.
| Command Name |
Purpose |
| setx 100 |
Sets the turtle's x-coordinate to +100
Moves it 100 points to the right of center
No vertical change |
| setx -200 |
Moves the turtle 200 points to the left of center
No vertical change |
| sety 150 |
Sets the turtle's y-coordinate to 150
Moves it 150 points above center
No horizontal change |
| sety - 50 |
Moves the turtle 50 points below center
No horizontal change |
| setxy 100 100 |
Moves the turtle to xy coordinate 100 100
|
show xcor
show ycor
|
Reports the turtle’s x-coordinate
Reports the turtle’s y-coordinate
|
setheading 0
seth 0
|
Points the turtle straight up, “high noon”
|
| seth 120 |
Moves the turtle 120 degree to point to the four o’clock position
|
The following screenshot is a practical demonstration of some of the above commands.
