Squeak

Introduction

Squeak is a dynamic environment of programming, conceived at the origin for educational applications. It is a powerful implementation of the language Smalltalk, based on a virtual Machine largely written in Smalltalk itself.

Squeak is resulting from work led initially to the Xerox PARK, then at Apple then finally at Disney Interactive by a team made up around daN Ingals and Alan Kay.

Initially conceived with the address of public young people or beginners in data processing, it is today the object of several contributions which exceed the framework of education strictly speaking. One can quote, among other, Croquet, a project of environment complete 3D or Kedama, a tool for simulation multi-agent.

Squeak and education

Squeak is the heir to the Logo in the approach which he proposes of the interaction data processing-education. It lies within the theoretical scopes of the Psychologie of the development and the ideas of people like Baldwin, Piaget or Vygotski. It is a data-processing environment of type Micromonde.

Alan Kay, one of the founding fathers of Squeak, originator of the Dynabook, encases thus the step with Papert and Minsky to propose an environment of programming bound for the children: the idea of this tool is to offer a big space of freedom, easily accessible, and in which the children will be able to express their ideas and to explore the consequences of them (see also Constructivisme, Théorie of the activity).

One of the aspects private individual to the Squeak environment is the concept of E-Toys, a concretization, in the form of drawings which one creates oneself, of the concept of object.

Squeak was retained to belong to the project One Laptop per Child.

Technical sides

Squeak is entirely programmed in Squeak, dialect of Smalltalk. The virtual Machine subjacent is written in Slang (a subset less directed object of Smalltalk) then translated into C by a Squeak program and compiled for the targeted platform.

In Squeak, one finds an implementation of Morphic, the graphic architectural structure of direct handling of objects of the computer programming language Self. Morphic is an alternative to the interface “Model View Controller” (MVC) traditional of Smalltalk-80, which remains however available in Squeak.

In addition, Squeak is directed multi-media. It integrates readers of formats wav, mp3, flash, deals with midday, the sound and vocal synthesis, the API 2D and 3D, character recognition, but also manages the network: waiter and navigator Web, dealt with of format XML, reader of email, etc

Based on a mechanism of virtual Machine, Squeak was related to many platforms. Thus, it is available on GNU/Linux, Microsoft Windows, BSD, Apple Mac OS X, BeOS, AmigaOS, like on some Personal assistants.

Environment of development

Squeak proposes a environment of development which comprises tools similar to those that one finds in all the environments Smalltalk (inspector of objects, naivgateurs of classes, tools of refactorisation), but of which some are more original:

Refactoring Browser : allows to easily visualize all the source code of Squeak arranged out of packages, classes, protocols and methods. It has functions for the transformations of code:

Renaming of a class, a method or a Variable automatically reflected on all the occurrences of the name of this class in the source code.
Creation in a click of the Accesseur S with the addition of a variable of authority.
Extraction of part of a method in another method (factorization of the code).

Method Finder : allows to find a method in all the code while giving him a parameter list (order nonnecessary) and an awaited result. Examples:

MethodFinder methodFor: # ((“Squeak has programming” 6 environment) “Squeak”)

turned over Résultat:

' (data1 truncateTo: data2) '

→ It is thus necessary to use the method truncateTo: to have the beginning of a character string.

MethodFinder methodFor: # (# (# (4 2 3 1)) # (1 2 3 4))

turned over Result:

' (data1 asSortedArray) (data1 leaves) '

→ There thus exist two methods to sort a table.

Workspace : allows to involve itself by typing Smalltalk orders and by seeing their results immediately.
Navigator for the unit tests, navigator for the management of version of the packages, etc

External bonds

the Squeak community in French (to download the francized last version of Squeak)
www.squeak.org, the official anglophone site
Squeak Swiki, a very complete information source
Squeakland, directed towards the related questions with education
a report on education with Squeak in Extrémadure (Spain)

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