Difference between revisions of "Tips"

Latest revision as of 04:25, 1 January 2009

Using Carbon Quick Edit (cQE).

Mops 5.3 was the first release to come bundled with Carbon Quick Edit (cQE). In addition to running "natively" under Mac OS X, Carbon Quick Edit now communicates properly with Mops using AppleEvents.

However, the changes needed to bring about these improvements renders Carbon Quick Edit incompatible with older releases of PowerMops 5 and all versions of 68k Mops (including the version bundled with modern releases). These releases still require the older "Classic" Quick Edit (QE).

(Should you need it, you can still download the last "Classic" Quick Edit from: <ftp://ftp.powermops.org/pub/legacy/QE353.sit.bin>.)

Source: Information gleaned from a news://comp.lang.forth.mac post by Doug Hoffman. (March 22, 2003)

How not to (ab)use locals.

Many older versions of Mops (including 68k Mops) will allow you to define and execute a word that passes values on the stack to its own local parameters.

An example of such a word might be:

: foo  1 2 3  { one two three -- } ;

Newer versions of Mops will compile such words without complaint, but a stack underflow will result when executed.

This is not a bug. But, it is something you should be aware of.

Source: Blatantly plagiarized from a news://comp.lang.forth.mac post by Doug Hoffman. (July 25, 2003)

An easy way to debug class definitions.

Like most OOP languages, Mops doesn’t provide a straightforward way to access an object’s ivars directly. At first glance, this would seem to complicate debugging class definitions!

For example:

:class foo  super{ object }
int x
:m put:  ( n -- )  put: x ;m
;class

In this case, the ivar x within any instance of class foo would not be publicly accessable by other objects or words in the program. (Which is generally the desired effect, except when debugging...)

Rather than implementing (and debugging) additional methods to facilitate direct access to an object’s ivars, try temporarily declaring your ivars outside (and obviously before) your class definition as normal objects. Now your variables are publicly accessible, and not hidden within the object.

Here is the same definition as before, but with x declared outside of the definition for debugging purposes:

int x
:class foo  super{ object }
:m put:  ( n -- )  put: x ;m
;class

It should now be trivial to access this object’s "ivar". (When using this technique, be careful when creating multiple instances of your debugged class, as all instances of that object will share a single instance of the variables defined outside the class definition!)

Once you are finished debugging your class definition, simply move your ivars back inside the class definition.

Easy, huh?

Source: Shamelessly stolen from a news://comp.lang.forth.mac post by Doug Hoffman. (February 19, 2004)

A few ways to lookup a word.

Have you ever forgotten what a word does? Or maybe just forgotten its name?

Here are a few "official" ways to look up a word:

1. The Mops Manual. This is generally the most comprehensive reference.
2. The Quick Edit Subject Glossary. Also a good reference, though a bit dated.
3. The Quick Edit online Glossary. A great way to quickly lookup a word’s description and syntax.
4. The word locate. (Also invocable with CMD-= within Quick Edit.) This word will look through the Mops source files and try to find the actual source definition where the word was defined.
5. The Quick Edit source browser. Use CONTROL-CLICK for class names and method names, and CONTROL-OPTION-CLICK for colon definitions.

Yet another effective method for finding a word name is wordsWith. Execute the following source from within a file...

need zstring+
string+ s1
string+ s2
: .id  ( xt -- )
   NAME? IF >name N>COUNT ( addr len )
           put: s2
           get: s1 search: s2
           IF all: s2 type cr 0 -> out THEN
       ELSE drop
       THEN ;
: doWith ( addr len -- )
   new: s1  new: s2  put: s1
   setToTop: theMark
   0 -> out cr
   BEGIN
       next: theMark
       ?dup
   WHILE
       link> .id
   REPEAT
   release: s1 release: s2 ;
: wordsWith
   bl word count ( addr len )
   doWith
   cr ." wordsWith done "   cr ;

Invoke like this:

wordsWith similarword

Source: Information and neat code snippet courtesy of a news://comp.lang.forth.mac post from (who else?) Doug Hoffman. (April 15, 2004)

Getting Mops to behave like a Standard Forth.

Are you eager to get started using Mops as an ANS Forth?

Do this:

1. Launch "PowerMops" (in the ’Mops ƒ’ folder).
2. In the Mops window, execute: // ANSI
3. Now save a snapshot. Execute: save mySnapshotName
4. Launch the PowerMops application called "mySnapshotName" (in the ’Mops ƒ’ folder) next time you use Mops.

(Remember to execute commands using the ENTER key, not RETURN.)

Mops will now behave as a Standard Forth, complete with the CORE, ERROR, and ERROR EXT wordsets. Most of the CORE EXT wordset is there, too.

Source: Information found in the Mops Manual. (March 16, 2004)