Shapes4Learn

What is it?

Shapes4Learn is an educational tool for students to practice formal language processing. It is a framework with an interpreter that receives commands as text and allows to create, delete and manipulate shapes.

What is it for?

It may be used as an introduction to Compilers since it can cover most of the phases: lexical, syntactical and semantic analysis, code optimization and translation. The only and main difference is that, instead of generating machine code, it will interact with the shapes engine.

Where is it used?

This framework is used for the Languages Processing course in Universidad Maimónides in Buenos Aires, Argentina.

How does it work?

Shapes4Learn defines a formal language for shapes creation and manipulation. The framework's main components are:

• Shapes: Basic objects that can be created, deleted and manipulated in Shape4Learn. In the current version, the implemented shapes are square and circle.
• Shape Ambient: This component is where shapes live and must keep track of them. Creation, deletion and manipulation actions are provided by this component. The core of Shapes4Learn provides a basic version called BasicShapeAmbient. It is available for users and it is widely used in the tests.
• Interpreter: This is the most important component of the framework because is the one that students must implement. It can be as simple or complex as the developer wants. Shape4Learn packages a trivial Interpreter implemented using regular expressions that is used in the tests.
• InterpreterTests: A Test Suite that must be passed by any implemented Interpreter.

Class diagram

Future steps

It is expected in the near future that Shapes4Learn will incorporate the next features:

• More commands in the language.
• More shapes: Triangle.
• More shapes attributes: movements and rotation.
• Better test coverage.

Longer term expected features:

• Control structures (loops).
• Relative attribute modifications ("increment position", "move right").

Shapes4Learn Language Documentation

About the tokens

In this language, tokens are mostly separated by whitespaces such as space, tab, CR or LF. The only exceptions are the numerical expressions and semi-colon. In the first case, whitespaces are not mandatory meaning that 4*(3+9) is valid but also 4 * (3+9 ). For semi-colons, they can be placed together with the last token of a sentence or separated.

Available commands

Create a shape in the Shape Ambient. The new shape will have the provided id:

create rectangle|circle [id];

Set the color to an already existing shape in the Shape Ambient. The shape must already exist:

setcolor [color_def] in shape [id];

Set the given base on the rectangle defined by the provided id:

setbase [expression] in rectangle [id];

Set the given height on the rectangle defined by the provided id:

setheight [expression] in rectangle [id];

Set the given radius on the circle defined by the provided id:

setradius [expression] in circle [id];

Set the 2D-position (x,y) for the shape given by the id: setposition [expression],[expression] in shape [id];

Defined Grammar (Incomplete)

A single letter in ascii alphabet:

[letter] := a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|A|B|C|D|E|F|G|H|I|J|K|L|O|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

An identifier for the source code:

[id] := [letter][id]|[letter]

A single digit:

[digit] := 1|2|3|4|5|6|7|8|9|0

A single hexadecimal digit:

[hexdigit] := [digit]|a|b|c|d|e|f|A|B|C|D|E|F

A color definition in RGB from #000000 to #ffffff:

[color_def] := #[hexdigit][hexdigit][hexdigit][hexdigit][hexdigit][hexdigit]

A number composed by a concatenation of one or more single digits:

[number] := [digit][number]|[digit]

A mathematical expression that supports numbers, addition, subtraction, multiplication, division and parenthesis. For example: 9+(4*(5-7)+8/2)

[expression] :=