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

Macs Fan Control 1.3.1.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
NetShade 6.3.1 - Browse privately using...
NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN servers spanning seven countries. NetShade masks your IP address as you... Read more
Dragon Dictate 4.0.7 - Premium voice-rec...
With Dragon Dictate speech recognition software, you can use your voice to create and edit text or interact with your favorite Mac applications. Far more than just speech-to-text, Dragon Dictate lets... Read more
Persecond 1.0.2 - Timelapse video made e...
Persecond is the easy, fun way to create a beautiful timelapse video. Import an image sequence from any camera, trim the length of your video, adjust the speed and playback direction, and you’re done... Read more
GIMP 2.8.14p2 - Powerful, free image edi...
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching,... Read more
Sandvox 2.10.2 - Easily build eye-catchi...
Sandvox is for Mac users who want to create a professional looking website quickly and easily. With Sandvox, you don't need to be a Web genius to build a stylish, feature-rich, standards-compliant... Read more
LibreOffice 5.0.1.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
f.lux 36.1 - Adjusts the color of your d...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
VirtualBox 5.0.2 - x86 virtualization so...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
File Juicer 4.43 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. In computer... Read more

ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
MacBook Airs on sale for $100 off MSRP
Best Buy has MacBook Airs on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary... Read more
Big Grips Lift Handle For iPad Air and iPad A...
KEM Ventures, Inc. which pioneered the extra-large, super-protective iPad case market with the introduction of Big Grips Frame and Stand in 2011, is launching Big Grips Lift featuring a new super-... Read more
Samsung Launches Galaxy Tab S2, Its Most Powe...
Samsung Electronics America, Inc. has announced the U.S. release of the Galaxy Tab S2, its thinnest, lightest, ultra-fast tablet. Blending form and function, elegant design and multitasking power,... Read more
Tablet Screen Sizes Expanding as iPad Pro App...
Larger screen sizes are gaining favor as the tablet transforms into a productivity device, with shipments growing 185 percent year-over-year in 2015. According to a new Strategy Analytics’ Tablet... Read more
Today Only: Save US$50 on Adobe Elements 13;...
Keep the memories. lose the distractions. Summer’s winding down and it’s time to turn almost perfect shots into picture perfect memories with Elements 13. And get the power to edit both photos and... Read more
1.4GHz Mac mini on sale for $449, save $50
Best Buy has the 1.4GHz Mac mini on sale for $50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Price for online orders only, in-store price may vary... Read more
12-inch 1.1GHz Gold MacBook on sale for $1149...
B&H Photo has the 12″ 1.1GHz Gold Retina MacBook on sale for $1149.99 including free shipping plus NY sales tax only. Their price is $150 off MSRP, and it’s the lowest price available for this... Read more
27-inch 3.3GHz 5K iMac on sale for $1849, sav...
Best Buy has the 27″ 3.3GHz 5K iMac on sale for $1849.99. Their price is $150 off MSRP, and it’s the lowest price available for this model. Choose free shipping or free local store pickup (if... Read more
Worldwide Tablet Shipments Expected to Declin...
Does Apple badly need a touchscreen convertible/hybrid laptop MacBook? Yes, judging from a new market forecast from the International Data Corporation (IDC) Worldwide Quarterly Tablet Tracker, which... Read more

Jobs Board

*Apple* Music, Business Operations - Apple (...
**Job Summary** This role in Apple Music and in iTunes is working with…the songs that we all enjoy listening to in Apple Music. Your job will be to work wit Read more
Hardware Systems Integration Engineer - *App...
**Job Summary** We are seeking an enthusiastic electrical engineer for the Apple Watch team. This is a design engineering position that entails working with Read more
Engineering Project Manager - *Apple* TV -...
**Job Summary** The iTunes Apps project management team oversees iTunes, Apple TV, DRM and iOS Applications. We are looking for a project manager to help manage and 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
*Apple* Retail Online Store: Customer Insigh...
**Job Summary** Apple Retail (Online Store) is seeking an experienced e-commerce analytics professional to join the Customer Insights Team. The Web e-Commerce Analyst Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.