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

1Password 5.1 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
GarageSale 6.9.2 - Create outstanding eB...
GarageSale is a slick, full-featured client application for the eBay online auction system. Create and manage your auctions with ease. With GarageSale, you can create, edit, track, and manage... Read more
calibre 2.17 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
OmniGraffle Pro 6.1.2 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.1.2 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
RoboForm 2.0.2 - Password manager; syncs...
RoboForm is a password manager that offers one-click login, mobile syncing, easy form filling, and reliable security. Password Manager. RoboForm remembers your passwords so you don't have to! Just... Read more
Apple MainStage 3.1 - Live performance t...
Love the sound you got on your recording? MainStage 3 makes it easy to bring all the same instruments and effects to the stage. Everything from the Sound Library and Smart Controls you're familiar... Read more
Freeway Pro 7.0.2 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
A Better Finder Rename 9.44 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
Stacks 2.6.9 - New way to create pages i...
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

This Week at 148Apps: January 19-23, 201...
Warm Your Winter With New Apps!   How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you’re looking for. The ones we love become Editor’s Choice, standing out... | Read more »
Eggmaster Review
Eggmaster Review By Jennifer Allen on January 26th, 2015 Our Rating: :: BRIEFLY COMPELLINGUniversal App - Designed for iPhone and iPad Tap like crazy to gain eggs, so that you can buy upgrades to gain more eggs, and so on. It... | Read more »
Cloudy Or Dry – Funny Or Die Release a W...
Cloudy Or Dry – Funny Or Die Release a Weather App Posted by Ellis Spice on January 26th, 2015 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Mediocre, the Team Behind Smash Hit, is...
Mediocre, the Team Behind Smash Hit, is Teasing Their Latest Unnamed Project Posted by Jessica Fisher on January 26th, 2015 [ permalink ] | Read more »
Heroes of Gaia Review
Heroes of Gaia Review By Campbell Bird on January 26th, 2015 Our Rating: :: TIMERS OF MIGHT AND MAGICUniversal App - Designed for iPhone and iPad This free-to-play rpg looks a lot like Heroes of Might and Magic, but it’s poor... | Read more »
Choice Provisions is Set to Launch Destr...
Choice Provisions is Set to Launch Destructamundo on iOS This Month Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] Choice Provisions – home stable to | Read more »
King of Thieves – An Interview With Zept...
Ahead of the release of ZeptoLab’s King of Thieves, we were able to ask ZeptoLab’s co-founder, Semyon Voinov, a few questions about the inspiration behind the game and what that means for the Cut the Rope franchise. | Read more »
Handle Review
Handle Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: SPEEDY ORGANIZINGUniversal App - Designed for iPhone and iPad Handle is a very convenient way of juggling your emails, To Do list, and Calendar all through one... | Read more »
The New Disney Inquizitive App Offers a...
The New Disney Inquizitive App Offers a Place for Fans to Take Disney Quizzes Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] | Read more »
Hands-On With Cut the Rope Developer Zep...
Marking quite a departure from ZeptoLab’s past successes, namely the Cut The Rope series, King of Thieves is shaping up to be quite promising. Due for release in February, we were lucky enough to have some time with a preview build to see exactly... | Read more »

Price Scanner via MacPrices.net

MasterCard Brings Contactless Payment, Apple...
MasterCard, the official card of the Waste Management Phoenix Open, and the PGA TOUR are bringing the latest payment technology to the spectator experience with the introduction of contactless... Read more
Petitioning Dropbox For Mac OS X 10.4 and 10....
Last week Dropbox announced to its users that app support for Mac OS X 10.4 and 10.5 will end May 18 — disappointing news for those of us who are still getting useful service out of older PPC Macs... Read more
Stop Street Harassment, Bullying, and Assault...
The STOP-ATTACK (http://www.stop-attack.com) app will leverage smartphone technology to make the world a safer place. Whether it’s bullying, street harassment or something even more sinister, the app... Read more
Stir Kinetic Desk M1 Standing Or Sitting Desk...
The age of the standing desk is upon us, and according to medical research, it’s arriving none too soon. The World Health Organization (WHO), reports that 60 to 85 percent of people worldwide lead... Read more
Bosch Opens North American eBike Conversion H...
Following its entry into the U.S. eBike market in early 2014, Bosch has established a new headquarters office for Bosch eBike Systems (http://www.bosch-ebike.us) in Southern California, expanding the... Read more
13-inch 2.4GHz Retina MacBook Pro (Apple refu...
The Apple Store has previous-generation Apple Certified Refurbished 13″ 2.4GHz/128GB Retina MacBook Pros available for $999. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.4GHz/... Read more
13-inch 2.6GHz Retina MacBook Pro on sale for...
Adorama has the 13″ 2.6GHz/128GB Retina MacBook Pro on sale for $1189.99, $110 off MSRP. Shipping is free, and Adorama charges NY & NJ sales tax only. Read more
College Student Deals are back, additional $5...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through April 11, 2015. Anyone with a valid .EDU email address can take advantage... Read more
iPhone 6 and 6 Plus GIve Apple Half Of US Mob...
Chicago-based Consumer Intelligence Research Partners, LLC (CIRP) have released analysis of the results of its research on mobile phone manufacturers for the calendar quarter that ended December 31,... Read more
Save $100 on MacBook Airs with 256GB of stora...
B&H Photo has 256GB MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.4GHz/256GB MacBook Air: $999 $100 off MSRP - 13″ 1.4GHz/256GB MacBook... Read more

Jobs Board

Detailer *Apple* Ford Body Shop / Collision...
Apple Automotive is one of the fastest growing dealer…and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive , Read more
*Apple* Acura/Subaru Service Technicians - A...
Apple Automotive is one of the fastest growing dealer…and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive , Read more
Business Development Manager - *Apple* Pay...
**Job Summary** Apple Pay is seeking an experienced business development manager to support the identification, recruitment, negotiation and ongoing management of Read more
*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.