I have been putting more of my free time into digesting Scheme. I am now working on XEmacs. After several stops and starts with emacs in the past, I am finally using it (might I add - productively) to write scheme code. I figured that even if emacs is of no use to me for most of my work, I could atleast use it to write scheme code. It should be good for that for sure.

Don’t misunderstand me when I say this, because you may have different opinion, especially if you have lived in Unix for a long time – which I haven’t. XEmacs still leaves me feeling like I am taking piano classes. I use Scite and Visual Studio for most of my day to day work.  Of course, if I am writing a document, then it is Word. I also have a love-hate relationship with Rob Pike’s Sam editor.

For a long time I used the old Turbo C++ IDE in DOS (yes I am not ashamed to confess) and it served me rather well. After which it was Visual Studio 5... it was a pain to use in some cases, but with this plug-in called ‘Whole Tomato’ that I used, it was a killer.

When I got started on Linux, editing was a real pain – it was like I had to learn to type all over again. That was major put-off. As a matter of fact I figured that I could not suffer the ‘miserable’ editors they have there and so decided to write my own editor. (Yes, I was crazy enough to try and write an editor instead of learning arcane key combinations…) Of course, since I could edit code on Linux, I decided to write my editor in a portable way in DOS and then figure out how to take it to Linux.

As most DOS code was written those days, I wrote interesting text mode menu libraries and such other things that assumed that I had access to VGA text buffer to access. Finally when I actually had something going, I decided to make the big switch – Prot to Linux. Almost immediately, I hit a blank wall.

The entire style of programming, with direct access to video memory that was used to write large Text-UI based apps on DOS, was simply non-existent in Linux. That, I still remember, was such a major put off that I was going around cursing Linux to anyone who would listen to me. The only alternatives that I was left with, was to use some editors that did old Word-Star like CTRL-K based key combinations, which was rather irritating. I also spent half a day looking at the ncurses lib that time, hoping for a way out. All I got was buggy behavior and one buggy lib after the other and numerous dependencies on some .so or the other which I had to go and find on the net .

Finally my entire work on the editor on Linux got scratched and I decided to turn it into a DOS only thing – which I used for much after that as file viewer. The thing was distributed as w.exe to my friends and the default config file used to display multicolor menu and the title “The Zen Masters Workbench”. In w.exe was viewer that could be given C like structures and could read data out of binary files to match the structures. That became the original basis for the implementation of my DDL language.

I don’t know why I typed all that down… anyway here is the little bit of scheme code that implements a for-loop as a macro. I know it is not much, but its good fun.

(require (lib "defmacro.ss"))

(define-macro for

  (lambda (init  cond  step  code)

    (let ((loop (gensym)))

      `(let ,loop ,init

             (if ,cond

                 (begin

                   ,code

                   (,loop ,step)))))))

;see nested for loops

(for ((i 1)) (< i 10) (+ i 1)

     (begin

       (for ((j i)) (< j 10) (+ j 1)

                (begin

                  (display i)

                  (display j)

                  (display " ")))

       (newline)))

Of course, written entirely in xemacs. One reason to use xemacs over Scite is that it gives me this really nice syntax driven indentation. The syntax high-lighting, for what I have seen, is pretty corny though. But on the whole, good enough to write scheme code for now.

If you are starting out on Scheme and already know how to program, I recommend Dorai Sitaram’s “Teach Yourself Scheme in Fixnum Days” as a starter. The SICP is a lovely text as well and full of ideas, but if you don’t have lots or free time on your hands and are not the sort who likes letting an idea go without giving it its due thought, then I wouldn’t recommend SICP. It will be a while before you get down to scheme-ing. Also Prof Kent Dybvig’s book on Scheme is good, but again if you are the impatient sort, the DS book is the better choice.

In a few weeks I should get my copy of the Little Schemer, I intend to be ready for it by then