TweetFollow Us on Twitter

Winter 91 - THE VETERAN NEOPHYTE

THE VETERAN NEOPHYTE

LISP, COLOR ICONS, AND LAYERS

DAVE JOHNSON

I recently started learning Lisp, in order to write a color icon editor for a project in ACOTSM (that's Apple Classroom of Tomorrow). The people behind ACOT are creating an environment in which kids can build and explore simulated ecologies, and I wanted to help, but didn't know Lisp well enough to be of much use. A color icon editor was needed, and it seemed like a straightforward and painless little project to cut my Lisp teeth on. Hah.

I did learn lots of Lisp, but I spent a disproportionate amount of time learning the low-level system interface in Macintosh Allegro Common Lisp (MCL) and wrestling Color QuickDraw to the ground. For you CopyBits fans, did you know that CopyBits always assumes that the destination PixMap is on the current GDevice? I guess I already knew this--it's documented all over the place--but the implications never affected me before. I needed to convert a 4-bit PixMap to 8 bits, so hey, let's use CopyBits, right? Wrong. The colors got munged every time, because color mapping kicked in and the source's color table didn't match the GDevice's. For the gory details, see Technical Note #277, especially the section on color mapping. If you like CopyBits, you'lllove this tech note.

I was curious what others thought of Lisp, so I asked around a little. Here are some of the responses I got:

Functional languages are cool if you have good libraries, but all those parentheses are a pain in the ass.
-- Bryan "Beaker" Ressler, C programmer.

It's the shortest distance between conception and realization.
-- Matthew MacLaurin, self-admitted Lisp junkie.

I hate it.
-- Neil Day, who was forced to write the Tower of Hanoi iteratively in an introductory Lisp course.

It's a great productivity tool, and Common Lisp provides a rich (though perhaps Byzantine) programming environment.
--Gregg Williams, technical writer and sometime Lisper.

(expectant look)
-- Natty, my dog.

There are several immediately apparent things about Lisp that are foreign to people used to C or Pascal. Data typing is nonexistent unless you want it: Any variable can hold any type of data at any time. Functions can be data, too, and can be passed around all over the place. Everything is cozily wrapped in parentheses many levels deep (after a while, this is somehow comforting). Context is all important and omnipresent. Changes can be immediately tried out, so forprototyping (and for those of us who thrive on immediate gratification) it's a joy to work in. For those lacking in discipline, Lisp can help to create a real mess (of course, any language can do that for you, it's just easier in Lisp). Because it is so forgiving, it encourages my own built-in "middle-out" design

strategy, which in the long run isn't terribly efficient, although lots of fun. With a little self-control, of course, this problem would go away (left as an exercise for the reader).

Writing Lisp code that is QuickDraw intensive is kind of a pain at first. MCL provides great libraries for basic QuickDraw tasks, but if you want to get fancy, you have to do it yourself. For the icon editor, I needed lots of little utility routines to do stuff like find a particular color's pixel value in the color table, add a color to a color table, copy a cicn, change the depth of a cicn, build new cicns from scratch. Nearly half my code consists of these little utilities. They'd be needed regardless of the language, I guess, but writing them in Lisp required me to learn the low-level system interface much more thoroughly than I originally intended. This made me grumble a little, but after I'd gotten over the initial syntactical hump, low-level access became transparent and largely effortless.

The other half of the code was much Lispier. I used the built-in object system (Object Lisp, since I was using MCL 1.3.2. Now, in MCL version 2.0, it's the Common Lisp Object System, or CLOS), and I found that it successfully isolated me from most of the grungy system details like events and window handling (that's what it's supposed to do, right?). I haven't done a lot of object programming, so I can't make incisive comparisons with other object systems, but I liked it.

The sort of layered, threaded structure of Lisp, and the continual "level switching" I had to do during development, got me thinking about how the machine is getting progressively more distant from the software I write. It seems that I write software to live on top of other software, not software to live on a machine. Object programming is a kind of layer creation, in that a well- designed object hides lots of details from the user of the object. MacApp is a layer (a thick one), HyperCard is also a layer (a really thick one), the Mac ® Toolbox is a layer, and so on.

More and more, programmers need to be comfortable stuffed between these layers. Here's the hard truth: YOU NO LONGER HAVE TOTAL CONTROL OF THE MACHINE. Once upon a time, in the dim and distant past, programmers had absolute power over every aspect of the computer. There wasn't even any such thing as a user! A programmer was God in a monotheistic universe. Now there are all sorts of software smoke screens between your code and the machine itself. You are no longer God; at best, you are a minor demigod in charge of shoes, or something. A long time ago I read a discussion of Macintosh programming, and one person compared it to sitting in a dark closet by yourself, and occasionally answering a note that is passed under the door from the outside. I think that's exaggerating a little, but the point is valid. You no longer need to know everything that's going on in the house; you can just be responsible for your own room. At least, that's the idea . . .

One persistent problem is that you have to depend on the reliability of the other code. When my icon editor was almost done, I found a memory leak. Two tiny handles were left on the heap after closing the editor. It took me almost a week (and some expert help) to track it down to a bug in the MCL object system. Obviously, this diluted the benefits gained by using the system.

Overall, though, I really do think that this division of labor, this layering, is a good thing. It lets people find the niche they like best, and ignore much of the rest if they want to. Often it is an incredible time-saver to learn to use others' code rather than learning to do what they did from scratch. Ideally, the layers will insulate you completely from irrelevant detail, and allow you to focus on your task. We're not there yet, but someday, maybe, you can actually stop inventing the wheel.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

jAlbum Pro 12.6.4 - Organize your digita...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.6.4 - Create custom photo gall...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
Microsoft Remote Desktop 8.0.16 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
Spotify 1.0.4.90. - Stream music, create...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
djay Pro 1.1 - Transform your Mac into a...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Vivaldi 1.0.118.19 - Lightweight browser...
Vivaldi browser. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind that users are... Read more
Stacks 2.6.11 - New way to create pages...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
xScope 4.1.3 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
Cyberduck 4.7 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Labels & Addresses 1.7 - Powerful la...
Labels & Addresses is a home and office tool for printing all sorts of labels, envelopes, inventory labels, and price tags. Merge-printing capability makes the program a great tool for holiday... Read more

Discover Your Reflexes With Minimalist G...
Discover O, BYOF Studios, may look simple at first with its' color matching premise and swipe controls, but as you speed up the task becomes more daunting. [Read more] | Read more »
Here's Another Roundup of Notable A...
Now that the Apple Watch is publically available (kind of), even more apps and games have been popping up for it. Some of them are updates to existing software, others are brand new. The main thing is that they're all for the Apple Watch, and if you... | Read more »
Use Batting Average and the Apple Watch...
Batting Average, by Pixolini, is designed to help you manage your statistics. Every time you go to bat, you can use your Apple Watch to track  your swings, strikes, and hits. [Read more] | Read more »
Celebrate Studio Pango's 3rd Annive...
It is time to party, Pangoland pals! Studio Pango is celebrating their 3rd birthday and their gift to you is a new update to Pangoland. [Read more] | Read more »
Become the World's Most Important D...
Must Deliver, by cherrypick games, is a top-down endless-runner witha healthy dose of the living dead. [Read more] | Read more »
SoundHound + LiveLyrics is Making its De...
SoundHound Inc. has announced that SoundHound + LiveLyrics, will be one of the first third-party apps to hit the Apple Watch. With  SoundHound you'll be able to tap on your watch and have the app recognize the music you are listening to, then have... | Read more »
Adobe Joins the Apple Watch Lineup With...
A whole tidal wave of apps are headed for the Apple Watch, and Adobe has joined in with 3 new ways to enhance your creativity and collaborate with others. The watch apps pair with iPad/iPhone apps to give you total control over your Adobe projects... | Read more »
Z Steel Soldiers, Sequel to Kavcom'...
Kavcom has released Z Steel Soldiers, which continues the story of the comedic RTS originally created by the Bitmap Brothers. [Read more] | Read more »
Seene Lets You Create 3D Images With You...
Seene, by Obvious Engineering, is a 3D capture app that's meant to allow you to create visually stunning 3D images with a tap of your finger, and then share them as a 3D photo, video or gif. [Read more] | Read more »
Lost Within - Tips, Tricks, and Strategi...
Have you just downloaded Lost Within and are you in need of a guiding hand? While it’s not the toughest of games out there you might still want some helpful tips to get you started. [Read more] | Read more »

Price Scanner via MacPrices.net

Zoho Business Apps for Apple Watch Put Select...
Pleasanton, California based Zoho has launched Zoho Business Apps for Apple Watch, a line of apps that extends Zoho business applications to let users perform select functions from an Apple Watch.... Read more
Universal Stylus Initiative Launched to Creat...
OEMs, stylus and touch controller manufacturers have announced the launch of Universal Stylus Initiative (USI), a new organization formed to develop and promote an industry specification for an... Read more
Amazon Shopping App for Apple Watch
With the new Amazon shopping app for Apple Watch, Amazon customers with one of the wearable devices can simply tap the app on the watch to purchase items in seconds, or save an idea for later. The... Read more
Intel Compute Stick: A New Mini-Computing For...
The Intel Compute Stick, a new pocket-sized computer based on a quad-core Intel Atom processor running Windows 8.1 with Bing, is available now through Intel Authorized Dealers across much of the... Read more
Heal to Launch First One-Touch House Call Doc...
Santa Monica, California based Heal, a pioneer in on-demand personal health care services — will offer the first one-touch, on-demand house call doctor app for the Apple Watch. Heal’s Watch app,... Read more
Mac Notebooks: Avoiding MagSafe Power Adapter...
Apple Support says proper usage, care, and maintenance of Your Mac notebook’s MagSafe power adapter can substantially increase the the adapter’s service life. Of course, MagSafe itself is an Apple... Read more
12″ Retina MacBook In Shootout With Air And P...
BareFeats’ rob-ART morgan has posted another comparison of the 12″ MacBook with other Mac laptops, noting that the general goodness of all Mac laptops can make which one to purchase a tough decision... Read more
FileMaker Go for iPad and iPhone: Over 1.5 Mi...
FileMaker has announced that its FileMaker Go for iPad and iPhone app has surpassed 1.5 million downloads from the iTunes App Store. The milestone confirms the continued popularity of the FileMaker... Read more
Sale! 13-inch 2.7GHz Retina MacBook Pro for $...
 Best Buy has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale for $1099 – $200 off MSRP. Choose free shipping or free local store pickup (if available). Price for online orders only, in-... Read more
Minimalist MacBook Confirms Death of Steve Jo...
ReadWrite’s Adriana Lee has posted a eulogy for the “Digital Hub” concept Steve Jobs first proposed back in 2001, declaring the new 12-inch MacBook with its single, over-subscribed USB-C port to be... Read more

Jobs Board

*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers 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* Support Technician IV - Jack Henry a...
Job Description Jack Henry & Associates is seeking an Apple Support Technician. This position while acting independently, ensures the proper day-to-day control of Read more
*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers Read more
*Apple* Software Support - Casper (Can work...
…experience . Full knowledge of Mac OS X and prior . Mac OSX / Server . Apple Remote Desktop . Process Documentation . Ability to prioritize multiple tasks in a fast pace Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.