I'm developing the new program Insphex (inspect hex), a hex dump tool that is created with and runs on the Medley Interlisp environment.

Similarly to the Linux command hexdump, it shows the contents of files as hexadecimal values and the corresponding ASCII characters. An early version of the program prints the hex dump to the standard output like this.

I plan to enhance Insphex to optionally display the dump in a separate window one page at a time. An attached menu will have options for showing the next page and exiting. I'll also provide an Exec command for running the program.

The code is in Common Lisp but will include some Interlisp to access the required system functionality.

Although Insphex is useful in itself, I have three main goals for it. First, I want a real project to practice the process for writing Common Lisp with the residential environment of Medley. This is the native way of coding on Medley and takes full advantage of its development environment and features such as the File Manager and the SEdit editor.

Most Medley tools and facilities are written in Interlisp or expose Interlisp APIs through which the functionality can be invoked. So another goal is to interface with Interlisp from Common Lisp to access the functionality I need like windows and menus.

My third goal is to experiment with displaying textual output in TEdit, the Medley word processor where the hex dump will optionally go.

Although the Interlisp API of TEdit supports advanced editing and formatting, Insphex does only basic text output. The primary feature I want is TEdit's ability to automatically handle repainting the window after it's resized or a hidden portion is exposed. This is handy as by default Interlisp windows mostly don't handle the repaint.

Now that the basic functionality of Insphex is in place I will implement displaying the hex dump in a TEdit window.

#insphex #CommonLisp #Interlisp #Lisp

Discuss... Email | Reply @amoroso@oldbytes.space

When the Medley Interlisp Project began reviving the system around 2020, its Common Lisp implementation was in the state it had when commercial development petered off in the 1990s, mostly prior to the ANSI standard.

Back then Medley Common Lisp mostly supported CLtL1 plus CLOS and the condition system. Some patches submitted several years later to bring the language closer to CLtL2 needed review and integration.

Aside from these general areas there was no detailed information on what Medley missed or differed from ANSI Common Lisp.

In late 2021 Larry Masinter proposed to evaluate the ANSI compatibility of Medley Common Lisp by running the code of popular Common Lisp books and documenting any divergences. In March of 2024 I set to work to test the code of the book Practical Common Lisp by Peter Seibel.

I went over the book chapter by chapter and completed a first pass, documenting the effort in a GitHub issue and a series of discussion posts. In addition I updated a running list of divergences from ANSI Common Lisp.

Methodology

Part of the code of the book is contained in the examples in the text and the rest in the downloadable source files, which constitute some more substantial projects.

To test the code on Medley I evaluated the definitions and expressions at a Xerox Common Lisp Exec, noting any errors or differences from the expected outcomes. When relevant source files were available I loaded them prior to evaluating the test expressions so that any required definitions and dependencies were present. ASDF hasn't been ported to Medley, so I loaded the files manually.

Adapting the code

Before running the code I had to apply a number of changes. I filled in any missing function and class definitions the book leaves out as incidental to the exposition. This also involved adding appropriate function calls and object instantiations to exercise the definitions or produce the expected output.

The source files of the book needed adaptation too due to the way Medley handles pure Common Lisp files.

Skipped code

The text and source files contain also code I couldn't run because some features are known to be missing from Medley, or key dependencies can't be fulfilled. For example, a few chapters rely on the AllegroServe HTTP server which doesn't run on Medley. Although Medley does have a XNS network stack, providing the TCP/IP network functions AllegroServe assumes would be a major project.

Some chapters depend on code in earlier chapters that uses features not available in Medley Common Lisp, so I had to skip those too.

Findings

Having completed the first pass over Practical Common Lisp, my initial impression is Medley's implementation of Common Lisp is capable and extensive. It can run with minor or no changes code that uses most basic and intermediate Common Lisp features.

The majority of the code I tried ran as expected. However, this work did reveal significant gaps and divergences from ANSI.

To account for the residential environment and other peculiarities of Medley, packages need to be defined in a specific way. For example, some common defpackage keyword arguments differ from ANSI. Also, uppercase strings seem to work better than keywords as package designators.

As for the gaps the loop iteration macro, symbol-macrolet, the #p reader macro, and other features turned out to be missing or not work.

While the incompatibilities with ANSI Common Lisp are relativaly easy to address or work around, what new users may find more difficult is understanding and using the residential environment of Medley.

Bringing Medley closer to ANSI Common Lisp

To plug the gaps this project uncovered Larry ported or implemented some of the missing features and fixed a few issues.

He ported a loop implementation which he's enhancing to add missing functionality like iterating over hash tables. Iterating over packages, which loop lacks at this time, is trickier. More work went into adding #p and an experimental symbol-macrolet.

Reviewing and merging the CLtL2 patches is still an open issue, a major project that involves substantial effort.

Future work and conclusion

When the new features are ready I'll do a second pass to check if more of the skipped code runs. Another outcome of the work may be the beginning of a test suite for Medley Common Lisp.

Regardless of the limitations, what the project highlighted is Medley is ready as a development environment for writing new Common Lisp code, or porting libraries and applications of small to medium complexity.

#CommonLisp #Interlisp #Lisp

Discuss... Email | Reply @amoroso@oldbytes.space

I finally fixed a longstanding duplicate definitions issue with Femtounit, my Interlisp unit test framework.

Femtounit creates a new File Manager type for unit tests, TESTS. DEFTEST, which defines a test, adds an entry of type TESTS and expands into an internal function that carries out the test when called. The problem was the File Manager noticed and tracked two objects for each DEFTEST, the TESTS entry and the function. But the function is an implementation detail that shouldn't be tracked by the File Manager or seen directly by the user.

To fix the issue, in the DEFDEFINER that creates the new type I added a call to UNMARKASCHANGED immediately after the definition of the internal function. UNMARKASCHANGED undoes the association with the File Manager the creation of the internal function establishes. I had tried DELDEF but it removes both the association and the internal function.

I also refactored the definition of the internal function to use DEFINEQ instead of assigning a LAMBDA to the function cell of the symbol naming the test, which is less clear and obscures the intent.

#femtounit #Interlisp #Lisp

Discuss... Email | Reply @amoroso@oldbytes.space

I got a cheap used copy of the book A Programmer's Guide to COMMON LISP by Deborah G. Tatar, Digital Press, 1987.

Why did I read such an old book, published a few years after CLtL1 and well before ANSI finalized the Common Lisp standard?

I'm always looking for good Lisp books. Since Medley is my primary Lisp environment, I'm particularly interested in books published when the system was originally developed and used. These works are relevant because they cover a set of features close to the state of the Common Lisp implementation of Medley, and present a programming style typical of Lisp development in those years.

Two old reviews got me curious about A Programmer's Guide to COMMON LISP, one by Daniel Weinreb and the other by Richard Caruana.

Both reviews point out the book is different from most contemporary introductory Lisp books which focus on AI. Although Tatar's does contain some AI code, such as an interesting and complete toy expert system, the sample code spans a wider range of domains like a text formatter similar to nroff.

What sets A Programmer's Guide to COMMON LISP apart from other Lisp books is its environment independent discussion of the interactive Lisp programming process. Writing code in the editor, evaluating expressions from the editor, interacting with the REPL for testing expressions and exploring, and so on.

I've never seen the process expressed so clearly in any book, past of present. I'm familiar with it but the material is particulary helpful for complete beginners.

Although the short chapter on macros presents some interesting examples like a simplified version of defstruct, it doesn't discuss gensym and variable capture. This is unusual. But it's only one of a few issues and the book is a valuable addition to my Lisp library.

#CommonLisp #books #Lisp

Discuss... Email | Reply @amoroso@oldbytes.space

Medley is a residential environment for Interlisp and Common Lisp development.

With some effort it's possible to use Medley as a traditional file based Common Lisp environment. But in specific cases a better approach is to bring in Medley's residential environment Common Lisp sources created in file based environments.

In this post I explain the latter, i.e. how to use TextModules to import Common Lisp files into the residential environment. I go over the steps for converting an example program, the database of CD music tracks in Chapter 3 Practical: A Simple Database of Peter Seibel's book Practical Common Lisp.

Motivation

Using the tools and facilities of the residential environment, such as the File Manager, is the normal way of developing new Lisp programs. To run existing Common Lisp code you don't plan to change often, you can also use Medley as a traditional file based environment.

For existing code written in file based environments you want to use and further develop in Medley, a better option is to import the code into the residential environment and continue working from there. This is what TextModules helps to do.

What is TextModules

TextModules is a Medley tool for bringing Common Lisp sources into the residential environment and place them under the control of the File Manager. It can also do the reverse, i.e. export the File Manager descriptions and metadata to Common Lisp sources accessible from file based environments.

Using TextModules is a one time process. You run the tool once to import the code, then use and modify it with the tools and facilities of the residential environment.

The documentation of textModules starts from page 305 (page 335 of the PDF) of the Lisp Library Modules manual.

Preparing the Common Lisp files

This example involves two of the source files of Seibel's book, packages.lisp and