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

PCalc 4.7 - Full-featured scientific cal...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
Duet 2.1.1.2 - Use your iPad as an exter...
Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable. Note: This app requires a $9.99 iOS companion app. Version 2.1.1.2:... Read more
Logitech Control Center 3.9.9 - Keyboard...
Logitech Control Center (LCC) is designed to support OS X and allows you to take full advantage of your Logitech keyboard, mouse, or trackball. With the LCC you can: Browse the Internet using... Read more
Tor Browser Bundle 9.0 - Anonymize Web b...
The Tor Browser Bundle is an easy-to-use portable package of Tor, Vidalia, Torbutton, and a Firefox fork preconfigured to work together out of the box. It contains a modified copy of Firefox that... Read more
OmniPlan Pro 3.13.1 - Professional-grade...
With OmniPlan Pro, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success... Read more
OmniPlan 3.13.1 - Professional-grade pro...
With OmniPlan, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success,... Read more
Final Draft 11.1 - Industry-leading scre...
Final Draft allows you to use your creative energy to focus on the content; let Final Draft take care of the style. Final Draft is the number-one selling application specifically designed for writing... Read more
ForkLift 3.3.5 - Powerful file manager:...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
Shredo 1.2.6 - $6.99
Shredo is a beautiful, functional file-shredding and privacy scan utility. It permanently shreds files, folders, and external volumes' contents to keep information secure and impossible for anyone to... Read more
Pixelmator 3.9 - Powerful layer-based im...
Pixelmator is a beautifully designed, easy-to-use, fast, and powerful image editor for OS X. It has everything you need to create, edit, and enhance your images. Pixelmator is a layer-based image... Read more

Latest Forum Discussions

See All

Bad North: Jotunn Edition guide
Bad North: Jotunn Edition can be cruel. You never quite know where your next attack is going to come from, and--even if you’re prepared for it--things might just not go your way. This doesn't mean the game is random, but it does have a peculiar... | Read more »
Renegade Racing is a hectic, wacky multi...
Earn to Die and Crash of Cars publisher Not Doppler is bringing its popular web game, Renegade Racing, over to mobile devices. It's a hectic, wacky multiplayer racer which sees you battling your way to victory in intense 1v5 matches. [Read more] | Read more »
Upcoming mobile MMO TeeTINY Online’s sec...
TeeTINY Online is an upcoming anime-themed MMO which boasts striking visuals and an ambitious open world to explore. Following a successful CBT (closed beta test) on Android, developer TEENY.studio has now released a follow-up test which adds an... | Read more »
Breakout: Dark Prison is a fast-paced ac...
Breakout: Dark Prison is an action RPG from LaterSoft. Set in the aftermath of a deadly virus outbreak your daughter has been taken from you because she has an immunity to the illness in her DNA. Not being a fan of experimentation on children –... | Read more »
Apple Arcade in review
This weekend, Apple Arcade will officially be one month old. That means anyone who signed up for the free trial on day one has a decision to make: Stick with the service and shell out $5 a month, or cancel and go about your merry way. | Read more »
Alluris is a choose-your-own adventure g...
Alluris is an RPG that the developer's are calling a swipe-your-own adventure game. This is because the game incorporates a Reigns-style - swiping left or right - selection mechanic to make all the decisions you'd usually expect to make across... | Read more »
Hello Hero All Stars receives update wit...
The first Hello Hero game hit global platforms in 2013 and proved a huge success, with developer Fincon adding two more entries to this popular series of casual RPG games since. Released in June this year, Hello Hero All Stars brings many of the... | Read more »
Zombieland: Double Tapper, a cartoon idl...
Zombieland: Double Tapper is the idle RPG tie-in to the upcoming Zombieland: Double Tap. Oddly, it's one of two different Zombieland games launching today, with the other being the Switch title Zombieland: Double Tap - Road Trip. [Read more] | Read more »
Apple Arcade: Ranked [Updated 10.15]
In case you missed it, I am on a quest to rank every Apple Arcade game there is. [Read more] | Read more »
Rusty Lake's The White Door launche...
Rusty Lake and Second Maze's intriguing point-and-click adventure game, The White Door, is now up for pre-order on the App Store. This one sees you playing as Robert Hill, a mental health patient who is suffering from severe memory loss. The game... | Read more »

Price Scanner via MacPrices.net

2019 15″ MacBook Pros back on sale for $200-$...
Apple resellers B&H Photo and Amazon have new 2019 15″ 6-Core and 8-Core Space Gray MacBook Pros on sale for up to $300 off Apple’s MSRP, including free shipping. These are the same MacBook Pros... Read more
Switch to Xfinity Mobile and lease any new Ap...
Xfinity Mobile will include a free $250 prepaid Visa card with the purchase of any new iPhone, new line activation, and transfer of phone number to Xfinity Mobile. Offer expires this coming Sunday,... Read more
8-Core iMac Pro on sale today for $4499 at B...
B&H Photo has the base 8-Core 3.2GHz 32GB/1TB iMac Pro on sale today for $4499 — $500 off Apple’s MSRP. Shipping is free. Their price is the lowest available for a new iMac Pro from any Apple... Read more
Apple Watch Series 3 GPS + Cellular models on...
Walmart has Apple Watch Series 3 GPS + Cellular models on sale today on their online store for $70 off Apple’s MSRP. These are the same Apple Watches sold by Apple in their retail and online stores.... Read more
The difference that is 2nd is the fact that o...
Clearly, article writing service is, in inclusion, comprised within the very long listing of our offers. You’ll be assured that you’re at the most reliable article writing support. Within this case... Read more
27″ iMacs available today at Adorama for up t...
Adorama has new 27″ 5K 6-Core iMacs in stock and on sale today for up to $114 off Apple’s MSRP with prices starting at $1699. Shipping is free. Adorama charges sales tax for NY & NJ residents... Read more
Apple now offering a full line Certified Refu...
Apple is now offering Certified Refurbished 12.9″ iPad Pros on their online store for up to $250 off the cost of new models. Prices start at $849. Each iPad comes with a standard Apple one-year... Read more
Boost Mobile offers iPhone 7 models for $100...
Boost Mobile has Apple 2017 iPhone 7 models now available starting at only $299, or $100 off MSRP: – 32GB iPhone 7: $299.99 – 128GB iPhone 7: $349.99 – 32GB iPhone 7 Plus: $399.99 – 128GB iPhone 7... Read more
Amazon offers $150 discount on 21″ 3GHz 4K 6-...
Amazon has the 2019 21″ 3.0GHz 4K 6-Core iMac on sale today for $1349.99 shipped. Their price is $150 off Apple’s MSRP, and it’s the cheapest price available for this model from any Apple reseller. Read more
11″ WiFi iPad Pros on sale today for up to $2...
Amazon has new 2018 Apple 11″ WiFi iPad Pros in stock today and on sale for up to $250 off Apple’s MSRP. These are the same iPad Pros sold by Apple in its retail and online stores. Be sure to select... Read more

Jobs Board

Best Buy *Apple* Computing Master - Best Bu...
**742338BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 001480-Christiana Mall-Store **Job Description:** **What Read more
*Apple* Mobility Pro-Store 149 (Towson) - Be...
**742252BR** **Job Title:** Apple Mobility Pro-Store 149 (Towson) **Job Category:** Store Associates **Location Number:** 000149-Towson-Store **Job Description:** At Read more
Best Buy *Apple* Computing Master - Best Bu...
**741931BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Location Number:** 000284-Elyria-Store **Job Description:** The Core Read more
Best Buy *Apple* Computing Master - Best Bu...
**742029BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Sales **Location Number:** 000571-Waterford Lakes-Store **Job Description:** **What Read more
*Apple* Mobility Pro - Best Buy (United Stat...
**742155BR** **Job Title:** Apple Mobility Pro **Job Category:** Store Associates **Location Number:** 000446-Waldorf-Store **Job Description:** At Best Buy, our Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.