TweetFollow Us on Twitter

March 93 - An Introduction to BETA: A New Object-oriented Language

An Introduction to BETA: A New Object-oriented Language

Steve Mann

New object-oriented products are announced every day. Most of them are based on a familiar language such as C++, SmallTalk, or LISP / CLOS. New object-oriented languages are another matter. When was the last time you saw an announcement for a commercial-grade object-oriented language product? BETA is such a product.

Development on BETA started in 1976 as a joint venture between several universities in Norway, Denmark, and Finland. This is the same computer science community (often called the Scandinavian School of object-orientation) that in the early 1960s developed Simula, the first object-oriented language. Throughout its formative years, the BETA research has been supported by grants from many companies, including Apollo, Apple, and Hewlett Packard. After more than 15 years of research and development, Mjolner Informatics has released the first commercial BETA product.


BETA is a completely new language with a design heavily influenced by its object-oriented predecessors, especially Simula. It is strongly typed like C++, with most type checking being done at compile time. The language design is based on a powerful abstraction mechanism called a pattern. The syntax for a pattern is:
<Pattern Name> :
    (#  <Attribute 1> ;
        <Attribute 2> ;
        <Attribute N> ;

    Enter <Input list>
    Do <Imperatives>
    Exit <Output list>

Attributes can be many things-the most common are object declarations and methods specific to the pattern being defined. The Enter statement lists the values passed to the Do section, Exit lists the values output from the Do section. The Do section contains imperative (executable) statements that perform actions. All the syntactic elements of a pattern are optional.

There are several types of patterns, including classes, procedures, functions, coroutines, processes, and exceptions. There are also three types of pattern derivatives:

  • subpatterns (like subclasses but more powerful),
  • virtual patterns (like C++ virtual procedures), and
  • pattern variables (variables that can be assigned any legal pattern value).

You can create any of these three derivatives from any of BETA's pattern types, making BETA a very orthogonal language. For instance, using subpatterns, you can create a hierarchy of procedures, functions, coroutines, processes, or exceptions, where all the subpatterns inherit attributes from their superpatterns. You can also define virtual classes, virtual procedures, virtual functions, and so on . Table 1 lists all the possible combinations of pattern derivatives and types.

Other important BETA features include:

  • class-less objects for one-of-a-kind object definitions;
  • direct and reference (pointer-based) attributes allowing the modeling of complex relationships;
  • block structures similar to Algol, allowing nested structures with local and global scopes for all patterns.


Here is a simple class pattern that defines a bank account object. It has three attributes-balance (a declaration using a predefined class pattern called integer), Deposit (a procedure pattern), and Withdraw (another procedure pattern).
Account :  (* a simple bank account class pattern *)   
    (#  balance : @ integer;        (* bank account balance *)

        Deposit :       (* add 'amount' to balance *) 
            (#  amount : @ integer          (* local declaration *)
            enter amount                    (* input list *)
            do balance + amount -> balance   (* action *)
            exit balance                        (* output list *)
        Withdraw :      (* subtract 'amount' from balance *)
            (#  amount : @ integer  
            enter amount    
            do balance - amount -> balance
            exit amount     

Note that:

  • Asterick/parens ('(*' and '*)') are used to enclose comments.
  • A colon (':') indicates a declaration.
  • An @ sign indicates the name of an object type.
  • Integer is a predefined BETA basic pattern (the other basic patterns are real, boolean, and char, plus there is a predefined text pattern that works much like strings).
  • Imperative statements always read left to right.

According to BETA terminology, both Deposit and Withdraw are procedure (not function) patterns. BETA procedures and functions both can have input and output lists. A BETA function computes a return value using only the input values, causing no side effects (a procedure may cause side effects).

The preceding sample is simply a class definition pattern with attributes (balance) and methods (Deposit and Withdraw). In order to create a complete BETA program, we need more, such as some declarations to create real account objects, and some imperatives to perform actions on those accounts:

(# (* a pattern with no name *)
    Account : (*  a pattern declaration within the unnamed pattern *)
        (#  acct_balance : @ integer;
            Deposit :                
                (#  amount : @ integer  
                enter amount
                do acct_balance + amount -> acct_balance
                exit balance    
            Withdraw :      
                (#  amount : @ integer  
                enter amount    
                do acct_balance - amount -> acct_balance
                exit amount     
            Balance :
                exit acct_balance
    A : @ Account;              
    cash_on_hand, balance : @ integer;  

do  100 -> &A.Deposit;               
    250 -> &A.Deposit;               
    75  -> &A.Withdraw -> cash_on_hand;   (* $75 on hand *)
    &A.Balance -> balance;                (* $275 balance *)

In BETA the symbol '&' means new; the expression &account.Deposit means "create a new instance of the pattern account.Deposit and execute it". This is basically the same as invoking a procedure. Note that the finished program, the primary object definition (Account), and the methods that operate on that account (Deposit, Withdraw, and Balance) are all patterns. This use of a single syntactic element to define everything and execute operations gives BETA much of its power and flexibility.


BETA allows you to define both static and dynamic reference attributes. The previous sample programs all have examples of static object references such as
A : @ Account;             
cash_on_hand, balance : @ integer;

Static objects are also called part objects (or part references) in BETA because the declared objects are a permanent part of the objects containing their declarations.

BETA also lets you define object references that denote different objects at different points in time (much like pointers). An example of a dynamic reference is

A : ^Account ;

The initial value of a dynamic reference is NONE (trying to reference an object attribute using a NONE pointer causes a runtime error). If we define an account using

A1 : Account ;

we can assign A1 to A using the statement

A1[] -> A[] ;

It is also possible to create objects dynamically by invoking their pattern as an executable statement. For instance, the statement


creates a new instance of an Account and returns a reference to that account. If we declare a reference object using

A1 : ^Account;

the following statement is valid:

&Account[] -> A1[];

The difference between &Account and &Account[] is important. The first means "generate an instance of Account and execute it"; the second means "generate a new instance of Account without executing it and return a reference to it".


When presenting a new language, there is always a certain amount of rote presentation to cover the basic syntax needed to create programs in that language. This section covers some of the more recognizable parts of BETA, including predefined basic patterns and attributes, arrays, assignment statements (evaluations), and control statements.

Basic Patterns

BETA has four predefined basic patterns : integer, real, boolean, and char. The default values and standard operators for BETA's basic patterns are shown in Table 2. In addition, BETA has a standard set of relational operators. Chars are ordered from 0 to 255, and false is less than true.

One unusual restriction that BETA has is that it is not possible to declare dynamic references to instances of these four basic patterns. Apparently this restriction is primarily for efficiency reasons.


BETA arrays (called repetitions) are defined using one of these two forms:
<Name>: [size] @<Type> ;       (* static repetition *)
<Name>: [size] ^<Type> ;        (* dynamic repetition *)

Array indices range from one to <Name>.range (range is an intrinsic attribute of all array objects). You can dynamically resize arrays using the extend attribute, which adds elements to an array. You can reallocate an array, initializing all the elements to the default value for the array object type. You can also assign array slices (or parts of an array).

Here are some array examples:

A1, A2 : [10] @integer;    (* integer arrays A1[1]-A1[10],
                              A2[1]-A2[10] *)
1050 -> A1.[1];         (* assignment *)
10 -> A1.extend;        (* resize A2 to 20 elements *)
25 ->;           (* resize and reinitialize A2 *)
A1 [1:5] -> A2 [10];    (* slice assignment *)

There is also a special repetition pattern called text which is derived from a string pattern. It is a character array, subject to all normal array operations, with additional predefined patterns for string manipulation.

For Statement

The BETA for statement is straightforward. It has the following form:
(for <Index>: <Range> repeat <Imperative-list> for)

<Index> is an integer object declared locally within the scope of the for statement. It cannot be changed within the loop. The index always starts at one and increments by one. A pattern with a for loop might look like

(#     sum: @ integer;
    V : [100] @ integer     (* integer array *)
do  (for i : V.range repeat i -> V [i] for)
    0 -> sum;
    (for i : V.range repeat sum + v [i] -> sum for)

It is possible to overcome the limitations of the for index structure (integer indices which always start at one and increment by one) using other patterns. That capability is not explored in this introductory article.

If Statement

The BETA if statement is an unusual combination of a traditional if statement and a case statement. Its form is
(if E0
    // E1 then I1
    // E2 then I2
        . . .
    //En then In
    else I

E1 . . . En are evaluations and I1 . . . In are imperatives. The else clause is optional. Here's an example of a simple if statement:

(if x
    // 17 then . . .
    // 33 then . . .
    // y+3 then . . .

A boolean evaluation (albeit an awkward one) might be written

(if (x > 0) and (y < 0)
    // True then . . .
    // False then . . .


BETA evaluation (assignment) statements are very flexible. You can define multiple assignment statements such as
   3 -> I -> J

You can also combine multiple assignments with pattern executions and enter and exit redirection like in this program:

   (#  Power :     (* compute X^n where n > 0 *)
        (#  X, Y : @ real; n : @ integer;
        enter (X, n) 
        do  1 -> Y;
            (for i : n repeat Y * X -> Y for)
        exit Y

        Reciproc :  (* compute (Q, 1/Q) *)
        (# Q, R : @ real;
        enter Q
        do  (if (Q // 0) then 0 -> R
            else (1 div Q) -> R
            if )
        exit (Q, R)
    A, B : @ real;
    do  (3.14, 2) -> &Power -> &Reciproc -> (A, B);
        (* A = 3.14 ^ 2, B = 1/A *)


So far I have described the more basic elements of the BETA language. There are many advanced capabilities, such as subpatterns and virtual patterns, exception handling, and concurrency, that really show off BETA's power as an object-oriented language and the depth of its design. I''ll cover these topics in a future article.

The Mjolner BETA System, created by several of the language's original designers, is currently the only commercial implementation of a BETA development environment. The Mjolner BETA System includes:

  • native code generation,
  • automatic garbage collection and storage management,
  • separate compilation of program fragments with automatic dependency analysis,
  • interfaces to C and assembly language modules (and Pascal on the Mac),
  • persistent objects, although not a full-blown object-oriented database (a complete OODB is expected by late 1993),
  • basic patterns for simple data types,
  • a set of container patterns for more complex data structures (including sets, has tables, stacks, queues, and lists),
  • stream patterns for text and file handling,
  • process management and concurrency control patterns, and
  • application frameworks for X Windows, Motif, and the Macintosh Toolbox.

As if that weren't enough, Mjolner also sells a variety of additional tools including a modifiable Hyper Structure Editor, a metaprogramming system, a BETA CASE Tool (Unix only), and a source-level debugger (Unix only). In the coming months we hope to present an overview of BETA's advanced features, a comprehensive review of Mjolner's BETA System and tools, and advanced programming examples. Let us know if there are specific topics you would like addressed. -

MADA is pleased to announce that as we were going to press with this issue, Mjolner selected MADA as their exclusive US and Canada distributor for the Macintosh version of BETA. We are also carrying the reset of the Mjolner BETA product line. See page 67 for more details.

In addition, a demo version of the Mjolner BETA System is available on MADA's "Five Years of Objects" CD-ROM.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Planet Diver guide - How to survive long...
Planet Diver is an endless arcade game about diving through planets while dodging lava, killing bats, and collecting Starstuff. Here are some tips to help you go the distance. [Read more] | Read more »
KORG iDS-10 (Music)
KORG iDS-10 1.0.0 Device: iOS iPhone Category: Music Price: $9.99, Version: 1.0.0 (iTunes) Description: ** Debut Discount: 50% OFF! Sale Price US$9.99 (Regular price US$19.99). Other all Korg apps are also 50% OFF until Dec 28! **... | Read more »
World of Tanks Generals guide - Tips and...
World of Tanks Generals is a brand new card game by the developer behind the World of Tanks shooter franchise. It plays like a cross between chess and your typical card game. You have to keep in consideration where you place your tanks on the board... | Read more »
TruckSimulation 16 guide: How to succeed...
Remember those strangely enjoyable truck missions in Grand Theft Auto V whereit was a disturbing amount of fun to deliver cargo? TruckSimulation 16 is reminiscent of that, and has you play the role of a truck driver who has to deliver various... | Read more »
The best GIF making apps
Animated GIFs have exploded in popularity recently which is likely thanks to a combination of Tumblr, our shorter attention spans, and the simple fact they’re a lot of fun. [Read more] | Read more »
The best remote desktop apps for iOS
We've been sifting through the App Store to find the best ways to do computer tasks on a tablet. That gave us a thought - what if we could just do computer tasks from our tablets? Here's a list of the best remote desktop apps to help you use your... | Read more »
Warhammer 40,000: Freeblade guide - How...
Warhammer 40,000: Freebladejust launched in the App Store and it lets you live your childhood dream of blowing up and slashing a bunch of enemies as a massive, hulking Space Marine. It's not easy being a Space Marine though - and particularly if... | Read more »
Gopogo guide - How to bounce like the be...
Nitrome just launched a new game and, as to be expected, it's a lot of addictive fun. It's called Gopogo, and it challenges you to hoparound a bunch of platforms, avoiding enemies and picking up shiny stuff. It's not easy though - just like the... | Read more »
Sago Mini Superhero (Education)
Sago Mini Superhero 1.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0 (iTunes) Description: KAPOW! Jack the rabbit bursts into the sky as the Sago Mini Superhero! Fly with Jack as he lifts impossible weights,... | Read more »
Star Wars: Galaxy of Heroes guide - How...
Star Wars: Galaxy of Heroes is all about collecting heroes, powering them up, and using them together to defeat your foes. It's pretty straightforward stuff for the most part, but increasing your characters' stats can be a bit confusing because it... | Read more »

Price Scanner via

World’s First USB-C Adapter For MacBook Suppo...
Innergie, a brand of Delta Electronics, has announced its official release of the world’s first USB-C adapter supporting four DC output voltages, the PowerGear USB-C 45. This true Type C adapter... Read more
13-inch and 11-inch MacBook Airs on sale for...
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $120 off MSRP as part of their Holiday sale including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $819 $90 off... Read more
13-inch MacBook Pros on sale for up to $150 o...
Take up to $150 off MSRP on the price of a new 13″ MacBook Pro at B&H Photo today as part of their Holiday sale. Shipping is free, and B&H charges NY tax only. These prices are currently the... Read more
13-inch 128GB MacBook Air now on sale for $79...
Best Buy has just lowered their price on the 2015 13″ 1.6GHz/128GB MacBook Air to $799.99 on their online store for Cyber Monday. Choose free shipping or free local store pickup (if available). Sale... Read more
Best Buy lowers 13-inch MacBook Pro prices, n...
Best Buy has lowered prices on select 13″ MacBook Pros this afternoon. Now save up to $200 off MSRP for Cyber Monday on the following models. Choose free shipping or free local store pickup (if... Read more
Cyber Monday: Apple MacBooks on sale for up t...
Apple resellers have MacBook Pros, MacBook Airs, and MacBooks on sale for up to $250 off MSRP for Cyber Monday 2015. The following is a roundup of the lowest prices available for new models from any... Read more
Cyber Monday: Apple Watch on sale for up to $...
B&H Photo has the Apple Watch on sale for Cyber Monday for $50-$100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - Apple Watch Sport: $50 off - Apple Watch: $50-$100 off B... Read more
Cyber Monday: 15% off Apple products, and sto...
Use code CYBER15 on Cyber Monday only to take 15% on Apple products at Target, and store-wide. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-... Read more
iPad Air 2 And iPad mini Among Top Five Black...
Adobe has released its 2015 online shopping data for Black Friday and Thanksgiving Day. The five best selling electronic products on Black Friday were Samsung 4K TVs, Apple iPad Air 2, Microsoft Xbox... Read more
All-in-one PC Shipments Projected To Drop Ove...
Digitimes’ Aaron Lee and Joseph Tsai report that all-in-one (AIO) PC shipments may drop a double-digit percentage on-year in 2015 due to weaker-than-expected demand, although second-largest AIO make... Read more

Jobs Board

*Apple* New Products Tester Needed - Apple (...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, continues Read more
Software Engineer, *Apple* Watch - Apple (U...
# Software Engineer, Apple Watch Job Number: 33362459 Santa Clara Valley, Califo ia, United States Posted: Jul. 28, 2015 Weekly Hours: 40.00 **Job Summary** Join the Read more
SW Engineer - *Apple* Music - Apple (United...
# SW Engineer - Apple Music Job Number: 40899104 San Francisco, Califo ia, United States Posted: Aug. 18, 2015 Weekly Hours: 40.00 **Job Summary** Join the Android Read more
Sr Software Engineer *Apple* Pay - Apple (U...
# Sr Software Engineer Apple Pay Job Number: 44003019 Santa Clara Valley, Califo ia, United States Posted: Nov. 13, 2015 Weekly Hours: 40.00 **Job Summary** Apple Read more
*Apple* Site Security Manager - Apple (Unite...
# Apple Site Security Manager Job Number: 42975010 Culver City, Califo ia, United States Posted: Oct. 2, 2015 Weekly Hours: 40.00 **Job Summary** The Apple Site Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.