TweetFollow Us on Twitter

Forth Q and A
Volume Number:1
Issue Number:6
Column Tag:TECH NOTES

FORTH Q&A

By Jörg Langowski

Q: How can I write text and numbers to a window and have automatic wrap- around?

A: For one thing, Forth does not define the simple “.” or type words so as to provide an automatic CR when the end of the window is reached. This makes sense in some applications, such as printing out tables, when the window size is not known beforehand. On the other hand, it is rather annoying if one wants to test a simple definition to see half of the printout disappear off the right edge.

You might have noticed that the built-in Forth word, WORDS, does an automatic word wrap. So it almost looks like there is some hidden word in MacForth that tests for the end of the ‘screen’ and prints out a CR when it is reached. Lets look at the definition of WORDS, using the decompiler from an earlier issue of this journal. (I converted the BRANCHes to IFs etc. to make the code more readable). Please refer to figure 1.

: words
  context @ ?dup 
   if @ ?dup
     if dup @ + ( stack now contains address of latest definition )
        begin dup dup 1+ c@ swap c@ or while ( token <> 0 )
            2+ count 31 and 2dup 16 {2c7c} ( aha! hidden definition )
            dup {2c58} ( another one ) type 2 spaces
            + ( add name length, get next token )
        repeat
     drop then
   then;

Figure 1

The code is pretty sraightforward: The address of the CONTEXT vocabulary is put on the stack and the offset to the LATEST definition added to it. Then, after making sure it is not at the end of the list (token = 0), WORDS gets the name string of the definition and, after some manipulations, types it. The manipulations are done by two of those strange tokens that have no name associated with them, {2C7C} and {2C58}. They are defined as follows:

: {2c7c} col @ over wmod 1+ -
         dup {2c58} col @ if spaces else drop then ;

: {2c58} col @ +
         get.window +wbounds 6+ w@
         get.window +wline.height @ 7-
         w/ > if cr then ;

The first one, {2C7C} tabs to the next integer multiple of n, where n is the number on top of the stack, and wraps around if it would go beyond the limit of the window. The actual wraparound is done by {2C58}, which expects the number of characters to be output on top of the stack. It then compares the final cursor position to (right window edge)/(line height - 7), which is approximately the last column position in the window. If the string would print beyond this last position, a carriage return is output first. The ‘approximately’, by the way, is the reason why WORDS sometimes prints off the screen with non-standard text sizes. The remedy is to increase LINE.HEIGHT.

So you can very easily achieve automatic wrap when outputting text. For string output (with COUNT TYPE) you may redefine:

: wraptype dup 2c58 execute type ;

and any string you output using this word will automatically be confined to the window boundaries (more or less; in case of trouble change LINE.HEIGHT). For number output, you either have to know beforehand how many digits your number will have, or you write your number to string conversion routine and then use WRAPTYPE.

In the near future, we will solve the text output problem (and also the Cut/Paste problem) in a more elegant way by using the TextEdit functions. Stay tuned for an article on that.

Q: How can I get access to the toolbox routines that are not predefined in MacForth?

A: I hope your question has already been answered in one of my recent columns (there is this 3 months’ delay between writing the letter to us and getting the answer), but I’ll repeat that important point here.

MacForth provides defining words that support most of the toolbox routines. They are the following:

OS.TRAP - the address on top of stack (TOS) is an operating system trap, which is compiled into the definition of the following word. On execution, this word takes the 32-bit number on TOS, puts it into register A0 and executes the trap. The result is returned in the variable IO-RESULT.

MT - the address on TOS is a Pascal procedure type trap. All parameters to this procedure are 32-bit items. On execution, the trap is called with all the parameters passed through the stack. They have to be set up in the order given in the trap definition (in Inside Macintosh).

W>MT - the Pascal definition expects one 16-bit item on TOS. Therefore, the (32-bit) item on TOS is converted to a 16-bit item before the trap is called.

2W>MT - same as W>MT, the two topmost items on the stack are converted to 16 bits.

The third type of traps are Pascal function type traps. This means that you have to allocate space, either 16 or 32 bits, by pushing a zero before you push the arguments on the stack. This way, function type traps can be called through MT. For simple functions, MacForth provides four defining words that do this space allocation automatically:

FUNC>W - no argument, 16 bit result (converted to 32 bits)
FUNC>L - no argument, 32 bit result
W>FUNC>L - 16 bit argument, 32 bit result
L>FUNC>L - 32 bit argument, 32 bit result. 

For all other trap calls you have to write your custom stack set-up procedure, which is not too hard. The definition of NEW.CONTROL in the March issue gives an example for that. One important tool in writing such a toolbox trap definition is the routine PUSHW that changes TOS and the stack pointer in such a way that TOS is a 16-bit item:

: pushw s0 @ >r sp@ 2- s0 ! sp! r> s0 ! drop ;

Be cautious in using PUSHW; 16-bit pushes and calls that pull 16 bits have to match, otherwise the stack pointer may be 2 bytes out of frame.

Q: How do I use resources from MacForth?

A: The BLKS files contain no resources (as you might check using a resource editor - some of them are around now - or even a simple disk editor program). If you want to use the resource fork of a file, you have to generate the resources first with Rmaker (this program can also be found on several public domain disks). Rmaker, however, has the annoying habit of deleting the data fork of a file that is presented to him. Therefore, the correct procedure is to create a new file of the correct type and creator with Rmaker and put in the resources that you want. For example, the input to Rmaker might look like:

MyFile
BLKSM4TH

TYPE MENU
   ,1
\14

   ,2
Test
Item1
Item2
(-
Item4
Item5

This will create the file MyFile with the correct type (BLKS) and creator (M4TH) and put the Apple menu (ID=1) and a test menu (ID=2) into the resource fork. Of course, this file does not contain a data fork yet, so you have to add some blocks to it by executing

 “ MyFile” 1 assign
1 open
1 10 append.blocks

and you can put your Forth program text into those blocks. MacForth provides the word OPEN.RSRC for opening the resource fork of a file; you will have to read the resources through the appropriate toolbox routines, since there are no predefined words for getting resources from a file.

Since Forth programs are usually distributed in source form, however, I do not consider resources as critical as in other applications. However, if you develop stand-alone applications in Forth (I have not used Level 3 yet, but any comments are welcome), you might want to add the resources with Rmaker. I will deal with using resources in one of my next columns.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

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
teleport 1.2.1 - Use one mouse/keyboard...
teleport is a simple utility to let you use one single mouse and keyboard to control several of your Macs. Simply reach the edge of your screen, and your mouse teleports to your other Mac! The... Read more
Apple iMovie 10.0.8 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... 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 »
Entertain Your Pet With Your Watch With...
The Petcube Camera is a device that lets you use live video to check in on your pet, talk to them, and play with them using a laser pointer - all while you're away. And the Petcube app is coming to the Apple Watch, so you'll be able to hang out with... | Read more »
Now You Can Manage Your Line2 Calls With...
You'll be able to get your Line2 cloud phone service on the Apple Watch very soon. The watch app can send and receive messages using hands-free voice dictation, or by selecting from a list of provided responses. [Read more] | Read more »

Price Scanner via MacPrices.net

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
13-inch 2.7GHz Retina MacBook Pro for $1234 w...
Adorama has the 13″ 2.7GHz/128GB Retina MacBook Pro in stock for $1234.99 ($65 off MSRP) including free shipping plus a free LG external DVD/CD optical drive. Adorama charges sales tax in NY & NJ... Read more
13-inch 2.5GHz MacBook Pro available for $999...
 Adorama has the 13-inch 2.5GHz MacBook Pro on sale for $999 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP. 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

Jobs Board

*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
*Apple* Software Support - Xerox Corporation...
…Imaging 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.