CompSci 307 : Fall 2021

OOLALA: Logo Programming IDE

This language a simplified version of the one invented by Wally Feurzeig, Seymour Papert, and Cynthia Solomon at MIT that has been used to teach children to program all over the world.

Create an interactive development environment, IDE, that supports users to write basic Logo programs that produce drawings by moving a turtle around the screen with its pen down.

A Logo program is a set of instructions to control the current turtle(s) by moving them forwards, backwards, changing its heading, and showing/hiding them. In this way, drawings are created based on a turtle's state and that of its pen so it acts as a relative cursor, allowing users to understand geometry by imagining what they would do if they were the turtle (through body syntonic prediction and reasoning).

In addition to the UI features common to all applications, it should all allow the user to:

change the pen's thickness
set an image to use for the current turtle(s)
set the Home location to a specific xy-location (default is the center of the display)
view the current turtle(s) state (i.e., xy-location and heading)

Example

This is an example of a typical program:

Program Notes Output
# draw a square
fd 50
lt 90
fd 50
lt 90
fd 50
lt 90
fd 50
Move turtle forward 50 pixels (side 1)
Turn turtle left 90 degrees (right angle)
Move turtle forward 50 pixels (side 2)
Turn turtle left 90 degrees (right angle)
Move turtle forward 50 pixels (side 3)
Turn turtle left 90 degrees (right angle)
Move turtle forward 50 pixels (side 4)

Program	Notes	Output
# draw a square fd 50 lt 90 fd 50 lt 90 fd 50 lt 90 fd 50	Move turtle forward 50 pixels (side 1) Turn turtle left 90 degrees (right angle) Move turtle forward 50 pixels (side 2) Turn turtle left 90 degrees (right angle) Move turtle forward 50 pixels (side 3) Turn turtle left 90 degrees (right angle) Move turtle forward 50 pixels (side 4)

More examples are given here, but you are expected to make your own example files as well (including ones with syntactically incorrect programs).

Programs

Commands

Name Description

FD pixels Forward, moves current turtle(s) in its current heading by pixels distance

BK pixels Back, moves current turtle(s) backward opposite its current heading by pixels distance

LT degrees Left, turns current turtle(s) counterclockwise by degrees angle

RT degrees Right, turns current turtle(s) clockwise by degrees angle

PD Pen down, subsequent current turtle(s) moves leaves a visible trail

PU Pen up, subsequent current turtle(s) moves do not leave any visible trail

ST Show turtle, makes current turtle(s)'s graphical representation visible

HT Hide turtle, makes current turtle(s)'s graphical representation invisible

HOME Home, moves current turtle(s) to the center of the screen (0 0)

STAMP Stamp, draw the current turtle(s) image in its current position and heading, so the image remains after its turtle moves away

TELL turtle(s) Tell, sets turtles that will follow subsequent commands
note, if turtle has not previously existed, it is created and placed at the home location

Name	Description
FD pixels	Forward, moves current turtle(s) in its current heading by pixels distance
BK pixels	Back, moves current turtle(s) backward opposite its current heading by pixels distance
LT degrees	Left, turns current turtle(s) counterclockwise by degrees angle
RT degrees	Right, turns current turtle(s) clockwise by degrees angle
PD	Pen down, subsequent current turtle(s) moves leaves a visible trail
PU	Pen up, subsequent current turtle(s) moves do not leave any visible trail
ST	Show turtle, makes current turtle(s)'s graphical representation visible
HT	Hide turtle, makes current turtle(s)'s graphical representation invisible
HOME	Home, moves current turtle(s) to the center of the screen (0 0)
STAMP	Stamp, draw the current turtle(s) image in its current position and heading, so the image remains after its turtle moves away
TELL turtle(s)	Tell, sets turtles that will follow subsequent commands note, if turtle has not previously existed, it is created and placed at the home location

General notes about a program's syntax:

Tokens are separated by one or more spaces, tabs, or newlines
Command names are not case sensitive (even though they are shown below in all capital letters)
Ignore any lines that are empty, i.e., only zero or more spaces, or begin with comment character, "#"

Resources

Experiment with an in browser Logo environment.

Learn more about how the complete (and complex) Logo programming language works: