Path: bloom-beacon.mit.edu!news.media.mit.edu!uhog.mit.edu!MathWorks.Com!yeshua.marcam.com!usc!nic-nac.CSU.net!news.Cerritos.edu!news.Arizona.EDU!math.arizona.edu!CS.Arizona.EDU!not-for-mail From: icon-project@cs.arizona.edu Newsgroups: comp.lang.icon,comp.answers,news.answers Subject: Icon Programming Language FAQ Followup-To: comp.lang.icon Date: 6 May 1994 09:03:38 -0700 Organization: University of Arizona CS Department, Tucson AZ Lines: 402 Sender: icon@CS.Arizona.EDU Approved: news-answers-request@MIT.Edu Message-ID: <2qdpoq$od2@optima.cs.arizona.edu> Reply-To: icon-project@cs.arizona.edu NNTP-Posting-Host: optima.cs.arizona.edu Xref: bloom-beacon.mit.edu comp.lang.icon:961 comp.answers:5247 news.answers:19221 Archive-name: comp-lang-icon-faq Frequently Asked Questions About The Icon Programming Language last updated: 03/04/94 This FAQ answers various questions about the Icon programming language, ranging from what it is to how you can get it. This first version of the Icon FAQ is devoted to the issues that are likely to be of most interest to persons who don't know anything about Icon or who are relatively new to it. Future versions of this FAQ will answer questions from more experienced Icon programmers. This FAQ is written by Ralph Griswold with help from Cliff Hathaway, Clint Jeffery, and Gregg Townsend. Section I -- General Questions: I.1. What is Icon? I.2. What is Icon good for? I.3. Where did Icon come from? I.4. What does "Icon" stand for? I.5. On what computers does Icon run? I.6. Who did all these implementations? I.7. Are there other implementations in the works? I.8. Are there different versions of Icon? I.9. Which implementations of Icon have graphics/window capabilities? I.10. Where can I get Icon? I.11. Where can I get documentation about Icon? I.12. What is the Icon Project? I.13. Where can I find examples of Icon programs? I.14. What is Idol? I.15. How often is material in Icon's FTP area updated? I.16. How do I stay up to date with what's going on with Icon? I.17. Why isn't the Icon Newsletter available electronically? I.18. Is there a users' group for Icon? I.19. How do I get technical support? I.20. Is there an optimizing compiler for Icon? I.21. What do I need to run the interpreter? I.22. What do I need to run the compiler? I.23. Can I build my own implementation of Icon for a new platform? +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I.1. What is Icon? Icon is a very high level general-purpose programming language with extensive features for processing strings (text) and data structures. Icon is an imperative, procedural language with a syntax that is reminiscent of C and Pascal, but its semantics are at a much higher level than those languages. Icon has a novel expression-evaluation mechanism that integrates goal- directed evaluation and backtracking with conventional control structures. It has a string scanning facility for pattern matching that avoids the tedious details usually associated with analyzing strings. Icon's built-in data structures include sets and tables with associative lookup, lists that can be used as vectors or stacks and queues, and records. Icon is a strongly, though not statically, typed language. It provides transparent automatic type conversion. For example, if an integer is used in an operation that requires a string, the integer is automatically converted to a string. Several implementations of Icon have high-level graphics facilities with an easily programmed window interface. Icon manages storage automatically. Objects are created as needed during program execution and space is reclaimed by garbage collection as needed. The sizes of strings and data structures are limited only by the amount of available memory. I.2. What is Icon good for? As a general-purpose programming language with a large computational repertoire, Icon can be used for most programming tasks. It's at its best when used as a prototyping tool, for processing text, and when ease of programming is needed for experimental and research applications. Paradoxically, Icon is used most often for short, one-shot tasks and for very complex applications. Icon is designed to make programming easy; it emphasizes the value of programmer's time and the importance of getting programs to work quickly. This explains its usefulness for prototyping as well as the apparent paradox of applicability to simple and complex applications. I.3. Where did Icon come from? Icon is the latest in a series of high-level programming languages designed to facilitate programming tasks involving strings and structures. The original language, SNOBOL, was developed at Bell Telephone Laboratories in the early 60s. SNOBOL evolved into SNOBOL4, which is still in use. Subsequent languages were developed at The University of Arizona with support from the National Science Foundation. Incidentally, Icon bears little physical resemblance to SNOBOL4, although it has similar objectives and many similar capabilities. I.4. What does "Icon" stand for? The name Icon (which is not spelled ICON) is not an acronym nor does it stand for anything in particular, although the word iconoclastic was mentioned at the time the name was chosen. The name predates the now common use of "icon" to refer to small images used in graphical user interfaces. This latter usage sometimes causes persons to think mistakenly that Icon is designed to create or manipulate icons. There's not much that can be done about this. I.5. On what computers does Icon run? The implementation of Icon is highly portable. There are versions for the Acorn Archimedes, the Amiga, the Atari ST, IBM CMS and MVS, the Macintosh, MS-DOS, OS/2, UNIX, and VMS. Nearly 60 UNIX platforms are supported. Icon programs also are highly portable. Most Icon programs can run on any platform that supports Icon. I.6. Who did all these implementations? The original implementation of Icon for UNIX was done at The University of Arizona. Most of the other implementations originally were done by volunteers scattered around the world. It's worth noting that all implementations of Icon are based on the same source code, which is written in C. This contributes to the portability of Icon itself, as well as to the portability of programs written in Icon. I.7. Are there other implementations in the works? Yes, work is constantly underway on implementations of Icon for new platforms. Present projects include Windows NT, Win32, the DEC Alpha running under UNIX, and a new Macintosh implementation. I.8. Are there different versions of Icon? Icon has evolved through a series of versions with improved and extended capabilities. The latest major version number is 8. Recent changes and additions, notably in the graphics area, have brought the current level to 8.10. (Version 8.11 is, of course, in the works.) Most implementations are up to 8.10, although a few for less frequently used platforms are still at 8.0. Almost all 8.0 programs will run under 8.10. I.9. Which implementations of Icon have graphics/window capabilities? Icon's graphics facilities presently are supported on the OS/2, UNIX, and VMS implementations. The UNIX and VMS implementations use X, while the OS/2 implementation uses Presentation Manager. The NT, Win32, and DEC Alpha implementations that are in progress will support Icon's graphics facilities. A Macintosh implementation to support graphics also is in the works. I.10. Where can I get Icon? Most implementations of Icon are available via anonymous FTP to cs.arizona.edu in /icon. The directory /icon/binaries contains executable versions of Icon for several systems, including several popular UNIX platforms. The directory /icon/packages contains source code and related material. All directories have READ.ME files with additional information. Icon also is available on a variety of physical media for prices ranging from $15 to $50. Contact: Icon Project Department of Computer Science The University of Arizona Tucson, AZ 85721 602-621-8448 (voice) 602-621-4246 (fax) icon-orders@cs.arizona.edu (e-mail) f the Icon Newsletter for a listing of what's available and what the prices are. Purchases can be made by credit card (MasterCard, Visa, or Discover) or by check drawn on a bank with a branch in the United States and made payable to The University of Arizona. I.11. Where can I get documentation about Icon? The definitive work on Icon is the book The Icon Programming Language, Griswold and Griswold, Prentice-Hall, 1990, 368 pages, ISBN 0-13-447889-4. This book is a complete description and reference manual for Version 8 of Icon. There also is a book on the implementation of Icon: The Implementation of the Icon Programming Language, Griswold and Griswold, Princeton University Press, 1986, 336 pages, ISBN 0-691-08431-9. This book describes the implementation as of Version 6 of Icon. Although the implementation has changed somewhat since then, the basic structure is the same. Technical reports describing recent implementation changes are included with books purchased from the Icon Project. These books are available from the Icon Project or from any book store that handles special orders. Additional documentation is available via FTP in /icon/doc. Notable documents are: TR 90-6 an overview of Icon TR 93-9 graphics/window facilities IPD212 changes between Versions 8.0 and 8.10 There are manual pages for UNIX systems, but there is no complete on-line documentation. The Icon Newsletter, which includes topical material about Icon and a list of material available from the Icon Project, is published three times a year. Subscriptions are free; contact the Icon Project to get a copy of the latest Newsletter and to be put on the mailing list. The Icon Analyst, a technically oriented newsletter that features articles about programming, is published six times a year. There is a subscription fee for the Analyst. A sample copy is available on request. All back issues of both newsletters are available for purchase. I.12. What is the Icon Project? The Icon Project is a name used by the group at The University of Arizona that develops, implements, distributes, and supports the Icon programming language. The Icon Project is not commercial organization. It derives support from The University of Arizona, grants, and (primarily) revenue from the sale of program material and documentation. I.13. Where can I find examples of Icon programs? There is a large program library for Icon. It is an excellent resource for both new and experienced programmers, containing numerous examples of how to do things with Icon. The library also provides many useful applications, as well as hundreds of procedures that supplement Icon's built-in repertoire. The library, like other Icon material, is available via FTP (cd /icon/library) and on physical media from the Icon Project. I.14. What is Idol? Idol is an object-oriented extension to Icon that provides concepts such as classes and multiple inheritance. Idol is written in Idol and is distributed as part of the Icon program library. Idol runs on almost all of the platforms that Icon runs on. Additional Idol information is available from Clint Jeffery, jeffery@ringer.cs.utsa.edu. I.15. How often is material in Icon's FTP area updated? New material is added when it's available. Established implementations usually are only updated when there's a major new release. This typically is every year or two. The Icon program library is updated on a similar schedule. I.16. How do I stay up to date with what's going on with Icon? The best way to find out about developments related to Icon is to subscribe to the Icon Newsletter. It's free, but it is distributed only by postal mail, so you must provide a mailing address. You can stay up to date on the source code, which is changed much more frequently than the version on FTP is updated, by subscribing to the source update service, which provides a new version about three times a year. There also is a subscription service for updates to the Icon program library, which provides new material three or four times a year. See the Icon Newsletter for information about subscribing to these services. I.17. Why isn't the Icon Newsletter available electronically? The Icon Newsletter contains diagrams, images, and other material that cannot be rendered in plain ASCII text. The Newsletter is prepared with a desktop publishing system that produces PostScript, but the files are enormous -- too large to include in the Icon FTP area. Selected articles from the Newsletter are available by FTP in /icon/doc/articles. I.18. Is there a users' group for Icon? There is no official Icon users' group. The Icon Project maintains an electronic mailing list, icon-group@cs.arizona.edu. Mail sent to this address is forwarded to subscribers. To subscribe (or unsubscribe), send a message to icon-group-request@cs.arizona.edu. There is a gateway between icon-group and comp.lang.icon, an unmoderated newsgroup for discussing issues related to Icon. The gateway, which exchanges messages between the two systems, is imperfect and not under the control of the Icon Project. The newsgroup generally provides faster response than the mailing list. The newsgroup is less intrusive, but it sometimes suffers from inappropriate postings. The Icon Project usually sends messages of interest to the Icon community to icon-group. I.19. How do I get technical support? Free technical support is available from the Icon Project via electronic mail to icon-project@cs.arizona.edu or by fax, telephone, and postal mail to the Icon Project as listed above. Since the Icon Project is not a commercial organization, support is limited to what it can provide with its available resources. If the Icon Project cannot help with a problem (such as for a platform it doesn't have), it will attempt to provide a contact with someone who can help. I.20. Is there an optimizing compiler for Icon? Yes. The original implementation was an interpreter. An optimizing compiler was added a few years ago. The interpreter and compiler are largely source-language compatible. The interpreter is used by most Icon programmers because it gets into execution quickly and runs fast enough for most applications. The compiler is best suited for applications that require the fastest possible execution time. In this case, it's generally best to develop the program using the interpreter and then compile the final result for production use. I.21. What do I need to run the interpreter? The Icon interpreter will run on most computers. It requires a reasonable amount of memory, however. Under MS-DOS, the Icon interpreter needs 500KB of application RAM to work well. I.22. What do I need to run the compiler? The Icon compiler is another matter. It requires a C compiler, a fast CPU for tolerable compilation times, a considerable amount of disk space, and a lot of memory -- at least several megabytes. The Icon compiler generates C code, which must then be compiled to produce an executable program. The flexibility that Icon provides to programmers makes compilation technically difficult and the process requires a large amount of memory. The C code it produces is voluminous and stresses the most robust C compilers. Generally speaking, the Icon compiler is practical for platforms in the workstation class but not for most personal computers. Although the compiler can be built and made to run on 286 platforms running standard MS-DOS, only trivially small programs can be compiled. In principle, the Icon compiler is practical on MS-DOS 386/486 platforms with extended memory, but the limited availability of suitable 32-bit C compilers for this environment has discouraged the use of the Icon compiler on such platforms. I.23. Can I build my own implementation of Icon for a new platform? As mentioned above, Icon is written in C and the source code is available via FTP and the Icon Project. The existing implementations are testament to its portability. (a small amount of assembly-language code is required for a context switch, but this is only needed for an optional pressions -- that can be disabled without affecting most of Icon.) New ports involve platform-specific configuration parameters and, in some cases, platform-specific code. The feasibility of a new port and the amount of work it may take depends on the platform -- its architecture, its C compiler, and its environment. Ports to new UNIX platforms generally are easy, although novel architecture may present problems. Ports to new operating systems generally are more difficult, especially if Icon's graphics facilities are implemented. The Icon Project provides what help it can with new ports. In return, it asks that code related to the port to be returned to the Icon Project for inclusion in future versions of the source code for Icon. This makes the new port available to others as well as to the porter when Icon is updated.