TweetFollow Us on Twitter

January 93 - Dylan(tm) FAQ

Dylan(tm) FAQ

This memo answers questions which are frequently asked about the Dylan programming language. The latest version of this memo is available by anonymous ftp from cambridge.apple.com in the file /pub/dylan/dylan-faq.txt. We expect to make other Dylan documents available for ftp from the same directory.

The Dylan manual is not available in electronic form, but a bound copy may be requested by sending your name and address to dylan-manual-request@cambridge.apple.com. (Applelink users should send to dylan-request@ cambridge.apple.com@internet#.). As of this writing, there is no charge for the manual.

If you want to keep up with Dylan news, consider joining the info-dylan mailing list, described below.

General Questions About Dylan

What is Dylan?

Dylan is a new Object Oriented Dynamic Language (OODL), developed by the Eastern Research and Technology Lab of Apple Computer. Dylan was designed to make the advantages of OODLs available for commercial programming on a variety of computing devices. Dylan most closely resembles CLOS and Scheme. Other languages which influenced the design of Dylan include Smalltalk, Self, and OakLisp.

Dylan is consistently object-oriented. It is not a procedural language with an object-oriented extension. To this end, Dylan does not attempt to be compatible with any previously existing programming language.

What is the target audience for Dylan?

The target audience for Dylan is software application programmers, most of whom are currently using static languages such as C and C++. We realize that the current manual is more appropriate for people already familiar with OODLs. We have plans for additional documents directed at static language programmers.

How does Dylan differ from previous OODLs?

Dylan is designed to allow the powerful and flexible programming techniques and development environments associated with OODLs, while also allowing the small, fast delivered applications currently associated with static languages.

Unlike many dynamic languages, Dylan's design consciously enables the runtime environment to execute without the development environment present. In addition, Dylan will let you selectively 'turn-off' dynamic capabilities when they are no longer needed, allowing more efficient compilation.

Are there any public mailing lists for discussing Dylan?

Yes. There are four mailing lists of interest to the public. Three of these addresses have a corresponding administrative address. If you want to be added to or removed from a mailing list, send mail to the administrative address, not the mailing list address.
info-dylan@cambridge.apple.com
info-dylan-request@cambridge.apple.com
    (administration)
info-dylan-req@cambridge.apple.com@internet# 
    (administration from Applelink)

This is a two-way mailing list for discussing any and all issues related to Dylan.

announce-dylan@cambridge.apple.com
announce-dylan-request@cambridge.apple.com
    (administration)
announce-d-req@cambridge.apple.com@internet#
    (admin from Applelink)

This is a mailing list for major announcements about Dylan (new implementation availability, new manual availability, etc). This mailing list is for people who want to keep up on Dylan news, but don't want the quantity of mail that comes through info-dylan.

dylan-builders@cambridge.apple.com
dylan-builders-request@cambridge.apple.com
    (administration)
d-builders-req@cambridge.apple.com@internet#
    (admin from Applelink)

This is a two-way mailing list for people who are working on Dylan implementations or who are considering working on an implementation. If you want to join this list, please send mail describing your plans to dylan-builders-request.

dylan-comments@cambridge.apple.com

This is a one way mailing list for sending comments to the people working on Dylan at Apple. Most Dylan discussions can take place on info-dylan.

Does Apple have an implementation of Dylan?

Apple hasn't announced plans to release an implementation of Dylan. However, we are working on implementations, and our implementation efforts have been an important proving ground for the Dylan design.

Will there be Apple products based on Dylan?

Apple has not announced any use of Dylan in products.

Is Dylan related to the Apple PDA project called Newton?

No. Dylan is being created by Apple's Advanced Technology Group, and no product-specific implementations of Dylan have been announced yet. If you are looking for more information on Newton development, you need to contact the Newton Developer Relations at NEWTON.DEVS @applelink.apple.com.

Are there third-party implementations of Dylan available?

Several third-parties have expressed interest in implementing Dylan. A group at DEC has succeeded in implementing a language based on the Dylan manual. They describe it as follows:

Thomas, a compiler written at Digital Equipment Corporation's Cambridge Research Laboratory, is now available to the public. Thomas compiles a language compatible with the language described in the book "Dylan(TM) an object-oriented dynamic language" by Apple Computer Eastern Research and Technology, April 1992.

The Thomas system is written in Scheme and is available to run under any one of three public implementations of Scheme: MIT's CScheme, DEC's Scheme->C, and Marc Feeley's Gambit. It can run on a wide range of machines including the Macintosh, PC compatibles, Vax, MIPS, Alpha, and 680x0. Thomas generates IEEE compatible Scheme code. The entire system (including sources) is available by anonymous ftp from:

   crl.dec.com:pub/DEC/Thomas
    gatekeeper.pa.dec.com:pub/DEC/Thomas
    altdorf.ai.mit.edu:archive/Thomas

We've also made Thomas available in the Dylan ftp directory at cambridge.apple.com.

Thanks to Marc Feeley, Thomas embedded in Gambit is now available as a stand-alone Macintosh application. We've placed this in the ftp directory on cambridge.apple.com.

[MADA hopes to make Thomas available on a CD-ROM in the near future.]

Is Dylan a proprietary language? Why is the Dylan name trademarked?

We want Dylan to be available on as many computers as possible. To this end, we are encouraging groups outside Apple to implement Dylan.

It is our intention to license the Dylan trademark to any implementation which passes a standard test suite. The purpose of the trademark is to ensure quality and consistency among implementations.

What should I do if I want to implement Dylan?

Send mail to dylan-builders-request@cambridge. apple.com. We are putting together a program to support implementors, and we want to hear from you. (Applelink users should send mail to d-builders-req@applelink.apple.com @internet#.)

If you've written an implementation of Dylan and want to release it, please contact us for a trademark license.

Is the Dylan language design frozen?

We don't plan changes to the general structure of the language, but we expect to continue working on the details. We also expect to specify some extensions and libraries.

We welcome your comments on the Dylan design. Your feedback is very important to the further evolution of the language. We haven't specified a limited review period.

Please understand that because of the amount of mail we are receiving, we may not be able to respond to your message in detail.

Are design clarifications available?

We are working on design clarifications. They will be made available via anonymous ftp from cambridge.apple.com.

Is there a group which promotes the use of object-oriented dynamic languages?

Yes. There is an OODL special interest group of MADA. MADA is a group which champions object-oriented programming on the Macintosh. The OODL sig is currently focusing on Macintosh Common Lisp, but it intends to expand to other languages and environments.

To subscribe to the OODL sig mailing list from Applelink send mail to OODL.SIG. Internet subscriptions should be requested from oodl-sig-request@cambridge.apple.com.

Questions about the Dylan Language Design

Is Apple planning to specify an alternate syntax for Dylan?

Yes. We recognize that many people prefer an algebraic syntax, and we plan to create and document such a syntax for Dylan.

Are there plans to specify a standard i/o package for Dylan?

Simple i/o will probably be specified in an optional library, rather than in the core language. A single i/o system wouldn't make sense on all computing devices because of the variation in user interfaces and storage systems.

Will Dylan specify a standard threading mechanism?

We recognize that threads are important and that most implementations of Dylan will support them. We haven't yet decided whether a standard thread mechanism would be appropriate for all platforms.

Why is 'make' allowed to return a previously allocated instance, or an object which is an indirect instance of the class passed to 'make'?

We feel that this is a very important abstraction mechanism. A class should have flexibility in how it implements 'make', as long as the object returned fulfills the protocol of the class.

For example, this allows a library to document a single abstract class which is supported by several undocumented implementation classes. The abstract class can choose which implementation class to instantiate based on the additional arguments to 'make'. This allows optimizations which are transparent to the clients of the library.

The default method for 'make' of a user-defined class returns a fresh direct instance of the requested class.

The Dylan manual doesn't require implementations to optimize tail recursion. Was this an intentional omission, or an editorial oversight?

It was an editorial oversight. Dylan implementations will be required to be properly tail recursive.

The Dylan manual doesn't say much about modules. Will this be specified in the future?

Dylan modules will be further specified in an upcoming design note. At this time we expect modules to exist only at compile-time, not at runtime. Non-portable extensions may support runtime module operations.

Can the 'method' special form be used to create closures?

Yes.

I don't understand how setter variables work. Is 'setter' a special form?

'setter' just provides an alternate way to spell variable names. For example, the following are all legal spellings of variable names:
foo
bar
(setter foo)
(setter quux)

'setter' is pure syntax, and nothing more. It's probably unnecessarily confusing to make setter variables look like function calls. For this reason, we are considering changing the syntax of setter variables.

Why not just have 'setter' be a function which takes a getter functio as an argument and returns the corresponding setter function?

If we did this, the action of exporting a getter function would automatically export the setter as well. We believe that it's important to allow the getter and setter to be exported and imported independently. The design of setter variables allows this.

What kind of object is used to return multiple values?

When a function returns multiple values, the return values are not stored in a wrapper object; they are returned directly. For example, if a function returns "the values 4 and 5", it returns two integers. It does not return a data structure which contains two integers.

Returning multiple values is similar to calling a function with more than one argument. When passing multiple objects as arguments to a function, the objects do not have to be stored in a single data structure before they are passed.

Is the specification of sealing complete?

No. We expect the specification of sealing to evolve as we gain implementation experience.

At this point, we believe that sealing operations should be expressed declaratively, as compile-time operations, rather than as run-time operations. In the Dylan manual they are described as run-time operations.

Will Dylan include 'eval'?

Some implementations may choose to support 'eval', but we do not have plans to add it to the language standard. We feel that the delivery of applications which are space efficient requires the separation of development time activity from runtime activity.

Will Dylan include an application framework?

We recognize the value of application frameworks, especially cross-platform application frameworks. Unfortunately, because of the great variation in computing platforms, a single application framework will not be part of the Dylan language. On each platform, there should either be a Dylan-specific application framework, or Dylan should be able to use application frameworks written in other languages.

Will Dylan interface to other languages?

We recognize that seamless integration with other languages, especially C and C++, is essential. We are working on addressing this issue. The solutions may not be part of the Dylan language proper.
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Air Video Server HD 2.1.0 - Stream video...
Air Video Server HD streams videos instantly from your computer on your iPhone, iPad, iPod touch or Apple TV. No need to worry about converting or transferring files. We took everything that was... Read more
Duplicate Annihilator 5.7.5 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator... Read more
BusyContacts 1.0.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
Capture One Pro 8.2.0.82 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Backblaze 4.0.0.872 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac.With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
Little Snitch 3.5.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Monolingual 1.6.4 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. If you use your computer in only one (human) language, you... Read more
CleanApp 5.0 - Application deinstaller a...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Fantastical 2.0 - Create calendar events...
Fantastical is the Mac calendar you'll actually enjoy using. Creating an event with Fantastical is quick, easy, and fun: Open Fantastical with a single click or keystroke Type in your event details... Read more
Cocktail 8.2 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more

Pie In The Sky: A Pizza Odyssey (Games)
Pie In The Sky: A Pizza Odyssey 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A game about delivering pizza. In space. | Read more »
Android's Popular OfficeSuite Now A...
Once only available for Android devices, OfficeSuite has finally landed on the app store. The Mobile Systems app lets you view, edit, create, and share Word, Excel, and PowerPoint documents as well as convert them to/from PDFs. It's touted as being... | Read more »
Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »
Hands-On With Allstar Heroes - A Promisi...
Let’s get this out of the way quickly. Allstar Heroes looks a lot like a certain other recent action RPG release, but it turns out that while it’s not yet available here, Allstar Heroes has been around for much longer than that other title. Now that... | Read more »
Macho Man and Steve Austin Join the Rank...
WWE Immortals, by Warner Bros. Interactive Entertainment and WWE, has gotten a superstar update. You'll now have access to Macho Man Randy Savage and Steve Austin. Both characters have two different versions: Macho Man Randy Savage Renegade or Macho... | Read more »
Fearless Fantasy is Fantastic for the iF...
I actually had my first look at Fearless Fantasy last year at E3, but it was on a PC so there wasn't much for me to talk about. But now that I've been able to play with a pre-release version of the iOS build, there's quite a bit for me to talk... | Read more »
MLB Manager 2015 (Games)
MLB Manager 2015 5.0.14 Device: iOS Universal Category: Games Price: $4.99, Version: 5.0.14 (iTunes) Description: Guide your favorite MLB franchise to glory! MLB Manager 2015, officially licensed by MLB.com and based on the award-... | Read more »

Price Scanner via MacPrices.net

Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more
New 128GB MacBook Airs on sale for $50 off MS...
 B&H Photo has 128GB 11″ and 13″ 2015 MacBook Airs on sale today for $50 off MSRP including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air (Model #MJVM2LL/A): $849 $50 off... Read more
13-inch 2.6GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished 13″ 2.6GHz/128GB Retina MacBook Pros available for $979 including free shipping. Original MSRP for this model was $1299. Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Samsung Galaxy S 6 and Galaxy S 6 edge U.S. P...
Samsung Electronics America, Inc. has announced the Galaxy S 6 and Galaxy S 6 edge will be available in the U.S. beginning April 10, with pre-orders being accepted now. “We have completely reimagined... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Save up to $80 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $80 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1019 $80 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more
Färbe Technik Offers iPhone Battery Charge LI...
Färbe Technik, which manufactures and markets of mobile accessories for Apple, Blackberry and Samsung mobile devices, is offering tips on how to keep your iPhone charged while in the field: •... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.