BETA is a pure

object-oriented Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...

language originating within the "Scandinavian School" in object-orientation where the first object-oriented language

Simula Simula is the name of two simulation programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard. Syntactically, it is an approximate superset of ALGOL 6 ...

was developed.Source

Ole Lehrmann Madsen: An overview of BETA Among its notable features, it introduced

nested class In object-oriented programming (OOP), an inner class or nested class is a class declared entirely within the body of another class or interface. It is distinguished from a subclass. Overview An instance of a normal or top-level class can exist on ...

es, and unified classes with procedures into so called patterns. The project is inactive as of October 2020.https://beta.cs.au.dk/

Features

Technical overview

From a technical perspective, BETA provides several unique features. Classes and Procedures are unified to one concept, a

Pattern A pattern is a regularity in the world, in human-made design, or in abstract ideas. As such, the elements of a pattern repeat in a predictable manner. A geometric pattern is a kind of pattern formed of geometric shapes and typically repeated l ...

. Also, classes are defined as properties/attributes of objects. This means that a class cannot be instantiated without an explicit object context. A consequence of this is that BETA supports

es. Classes can be virtually defined, much like virtual methods can be in most object-oriented programming languages. Virtual entities (such as methods and classes) are never overwritten; instead they are redefined or specialized. BETA supports the object-oriented perspective on programming and has comprehensive facilities for procedural and functional programming. It has powerful abstraction mechanisms to support identification of objects, classification and composition. BETA is a statically typed language like Simula,

Eiffel Eiffel may refer to: Places * Eiffel Peak, a summit in Alberta, Canada * Champ de Mars – Tour Eiffel station, Paris, France; a transit station Structures * Eiffel Tower, in Paris, France, designed by Gustave Eiffel * Eiffel Bridge, Ungheni, M ...

and

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

, with most type checking done at compile-time. BETA aims to achieve an optimal balance between compile-time type checking and run-time type checking.

Patterns

A major and peculiar feature of the language is the concept of patterns. In another programming language, such as

, one would have several classes and procedures. BETA expresses both of these concepts using patterns. For example, a simple class in C++ would have the form class point ; In BETA, the same class could be represented by the pattern point: (# x, y: @integer #) That is, a class called ''point'' will have two fields, ''x'' and ''y'', of type

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

. The symbols ''(#'' and ''#)'' introduce patterns. The colon is used to declare patterns and variables. The ''@'' sign before the integer type in the field definitions specifies that these are integer fields, and not, by contrast, references, arrays or other patterns. As another comparison, a procedure in C++ could have the form int max(int x, int y) In BETA, such a function could be written using a pattern max: (# x, y, z: @integer enter (x, y) do (if x >= y // True then x -> z else y -> z if) exit z #) The ''x'', ''y'' and ''z'' are local variables. The enter keyword specifies the input parameters to the pattern, while the exit keyword specifies the result of the function. Between the two, the do keyword prefixes the sequence of operations to be made. The conditional block is delimited by ''(if'' and ''if)'', that is the if keyword becomes part of the opening and closing parenthesis. Truth is checked through ''// True'' within an if block. Finally, the assignment operator ''->'' assigns the value on its left hand side to the variable on its right hand side.

Hello world!

This snippet prints the standard line "Hello world!":

(#
do ’Hello world!’->PutLine
#)

References

External links