BETA (programming language): Difference between revisions

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{{Infobox programming language

| name = BETA

| logo =

| paradigm = [[Object-oriented programming|Object-oriented]]

| year =

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| typing =

| implementations =

| website = DHTSHGSHGSH{{URL|daimi.au.dk/~beta}}

| dialects =

| influenced_by = [[Simula]]

| influenced =

| operating_system =

| license =

| website = {{URL|daimi.au.dk/~beta}}

}}

'''BETA''' is a pure [[object-oriented]] language originating within the "Scandinavian School" in object-orientation where the first object-oriented language [[Simula]] was developed.<ref nameFDHSGHGDSHG==Features=="overview">Source: [http://daimi.au.dk/~beta/Papers/BetaOverview/BetaOverview.pdf] Ole Lehrmann Madsen: An overview of BETA</ref> Among its notable features, it introduced [[nested class]]es, and unified classes with procedures into so called patterns.

==Features==

===Technical overview===

From a technical perspective, BETA provides several unique features. Classes and Procedures are unified to one concept, a [[BETA pattern|Pattern]]. Also, classes are defined as properties/attributes of objects. This means that a class cannot be instantiated without an explicit object context. A consequenceDFHGSDHFVNFDUBV ofFUG thisUFIHG isUT thatHRHTRperspective BETAon supportsprogramming [[nestedand class]]eshas comprehensive facilities for procedural and functional programming. ClassesIt canhas bepowerful virtuallyabstraction mechanisms to support identification of definedobjects, muchclassification and composition. BETA is a statically typed language like virtualSimula, methods[[Eiffel can(programming belanguage)|Eiffel]] inand [[C++]], with most object-orientedtype programmingchecking languagesdone at compile-time.<ref Virtualname="overview"/> entitiesBETA (suchaims asto methodsachieve andan classes)optimal arebalance neverbetween overwritten;compile-time insteadtype theychecking areand redefinedrun-time ortype specializedchecking.

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 (programming language)|Eiffel]] and [[C++]], with most type checking done at compile-time.<ref name="overview"/> 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 [[C++]], one would have several classes and procedures.proceduresF BETAGHVTEH expressesGTH both of these concepts using patterns.TR#)

For example, a simple class in C++ would have the form

<source lang="cpp">

class point {

int x, y;

};

</source>

In BETA, the same class could be represented by the pattern

<pre>

point: (#

x, y: @integer

#)

</pre>

That is, a class called ''point'' will have two fields, ''x'' and ''y'', of type [[integer]]. 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.

Line 63 ⟶ 38:

}

</source>

In BETA, such a function could be written usingusingFH aGTR pattern x -> z

<pre>

max: (#

x, y, z: @integer

enter (x, y)

do

(if x >= y // True then

x -> z

else

y -> z

Line 77 ⟶ 45:

#)

</pre>

The ''x'', ''y'' and ''z'' are local variables. The '''enter''' keyword FGHTProgramming Language, [http://daimi.au.dk/~beta/Books/index.html]

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 ''-&gt;'' 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 program|"Hello world!"]]:<br>

<pre>

(#

do ’Hello world!’->PutLine

#)

</pre>

==Further reading==

*Ole Lehrmann Madsen, Birger Møller-Pedersen, Kristen Nygaard: Object-Oriented Programming in the BETA Programming Language, [http://daimi.au.dk/~beta/Books/index.html]

==References==