Archive for the ‘climacs’ Category

Climacs and Java

Wednesday, May 2nd, 2007


Hot on the heels of the rudiments of a C syntax for Climacs, I’m about to commit a Java(TM) syntax. This one is slightly better, and should lead to improvements in the C syntax, too. (And, eventually, some refactoring of the – many – common elements.) Like the C syntax, this one does not yet try to parse too much Java grammar, but in the absence of a preprocessing stage, I have less excuse. On the other hand, the progressive layering of things like annotations (which look to this non-Java person like an afternoon’s work with a thin macro layer over symbol plists) and generics make the Java grammar distinctly grody. It’s a pity about infix, too…

“Java” is a trademark or registered trademark of Sun Microsystems, Inc. in the United States and other countries. They have an awful lot.

C and Lisp and Climacs and stuff

Thursday, April 26th, 2007


As a diversion from all the things I promised myself I’d be doing after ilc07, I’ve ended up playing with a C language syntax (mode) for Climacs.

When previewing on #lisp, the first question everyone had was “how accurately does this parse C?” Well, the answer is: at the moment, not at all. And I thought that, in the presence of C’s textual preprocessing facility*, that’s the way it would have to be. But looking briefly at emacs’ cc-mode, it looks like it ends up doing the closest thing to a full parse anyway, so I have some way to go…

More seriously, the C syntax uses the same LR parsing infrastructure that the existing Lisp syntax uses, so I’ve begun to abstract that out into its own LR-parsing mixin syntax. (I love mixins.) But it’s early days yet.

(This posted to shame me into actually delivering a patch to McClim reasonably soon rather than waiting for things to bit-rot. Which is the other thing — the wonder that is Drei means that this syntax is available to all text gadgets in McClim. Think of the possibilities…)

* “Many other changes occurred around 1972-3, but the most important was the introduction of the preprocessor. … Its original version was exceedingly simple, and provided only included files and simple string replacements: #include and #define of parameterless macros. Soon thereafter, it was extended … to incorporate macros with arguments and conditional compilation. The preprocessor was originally considered an optional adjunct to the language itself. … This attitude persisted, and explains both the incomplete integration of the syntax of the preprocessor with the rest of the language and the imprecision of its description in early reference manuals.” Ritchie, The Development of the C Language, 1993, in History of Programming Languages-II ed. Thomas J. Bergin, Jr. and Richard G. Gibson, Jr. ACM Press (New York) and Addison-Wesley (Reading, Mass), 1996

Indenting LOOP

Saturday, July 29th, 2006

In working on indenting LOOP forms for Climacs (see the latest update here) I’ve come across a couple of competing ideas on how they should be formatted.

From cl-indent-patches.el (“Original version by rst” with patches by “salem” and “bromley” according to the header) we have the following “validation” (line numbers added by me):

 1 (loop for i from 0 below 2
 2       for j from 0 below 2
 3       when foo
 4         do (fubar)
 5            (bar)
 6            (moo)
 7         and collect cash
 8               into honduras
 9       else do ;; this is the body of the first else
10               ;; the body is ...
11               (indented to the above comment)
12               (ZMACS gets this wrong)
13            and do this
14            and do that
15            and when foo
16                  do the-other
17                  and cry
18       when this-is-a-short-condition do
19         (body code of the when)
20       when here's something I used to botch do (here is a body)
21                                                (rest of body indented same)
22       do
23    (exdented loop body)
24    (I'm not sure I like this but it's compatible)
25       when funny-predicate do ;; Here's a comment
26                               (body filled to comment))

The forms at issue are the DOs at 9-12 (and 25-6; compare with 20-21), 18-19 and 22-24. I would indent these like this:

 9       else do ;; this is the body of the first else
10              ;; the body is ...
11              (indented to the above comment)
12              (ZMACS gets this wrong)

(I see no reason for conforming to a dubious commenting style. But I’m interested to know why not doing so is “wrong”.)

18       when this-is-a-short-condition do
19                                        (body code of the when)

(I see no reason to special-case a “short-condition”, whatever that is.)

22       do
23         (exdented loop body)
24         (I'm not sure I like this but it's compatible)

(Exdenting is just gross – but “compatible” with what?)

Of course, I’m now doubting my own taste, so I’d be interested in what the Planet Lisp community thinks. Answers in the comments for summarising in a later edition…

Climacs Search

Saturday, May 27th, 2006

Climacs Search: Multiple Query Replace From Buffer

Climacs has a bunch of search commands, but it needs more!

What it has at the moment are many of the standard ones:

  • Incremental Search (forward and back) – C-s and C-r
  • String Search (and Reverse String Search)
  • Word Search (and Reverse Word Search)
  • Regex Search Forward and Regex Search Backward
  • How Many (lines after point match some regex)
  • Replace String (unconditionally)
  • Query Replace – M-%

and a few less common:

  • Multiple Query Replace
  • Query Exchange
  • Multiple Query Replace From Buffer

Incremental Search and Query Replace have a fair subset of the GNU emacs functionality in their loops. While in an incremental search you can switch direction, add a newline to the search string (C-j), snarf the next word into the search string (C-w), or the remainder of the line (C-y), or the top of the kill ring (M-y) etc. While in a query replace loop you can replace, skip, exit, replace and exit, or just replace the rest of the matches.

So far so good for the normal stuff. You’ll see that some functionality isn’t there yet. Partially this is just that no-one has gotten around to it (and if your favourite functionality is missing patches are appreciated!). But partially this is because climacs isn’t emacs, and we’re still feeling our way towards what is the best way to use the command-loop, in which a lot of CLIMy magic happens.

As an example of the issues, take the emacsly-traditional way of invoking a string search – C-s immediately followed by the command to exit the search (RET in GNU emacs, Altmode in TWENEX EMACS, etc). The Incremental Search command works by setting up a special command table (a CLIM object imaginatively named isearch-climacs-table) that maps gestures to commands (so that, for instance, C-j is mapped to com-isearch-append-newline). The gesture #\Newline invokes com-isearch-exit. But when the search string is empty, #\Newline should run the command String Search (or Reverse String Search, if we’re isearching backward). String Search prompts the user for a string to search for (!), and one of the beauties of CLIM is that the system handles this automatically. But not here, where we are inside another command (and, indeed, inside another command loop – but that’s another story), so for the moment I have to reach behind the curtain and pull a few levers myself:

(execute-frame-command *application-frame*
                       (funcall
                        *partial-command-parser*
                        (frame-command-table *application-frame*)
                        (frame-standard-input *application-frame*)
                        (if search-forward-p
                            `(com-string-search ,*unsupplied-argument-marker*)
                            `(com-reverse-string-search ,*unsupplied-argument-marker*))
                        0))


Obviously this is uglyrific, but the moral of the story isn’t that CLIM makes normal things hard (although there are some things about command tables that the CLIM 2 spec leaves rather underspecified), but that I don’t yet know the best way to get this (admittedly rather special) behaviour out of the existing command loop. (One possibility: have a pending-commands slot that the command-loop checks, analogous to the remaining-keys slot used by the keyboard macro machinery.)

Another thing I don’t understand is why GNU emacs doesn’t have a command like Multiple Query Replace. This prompts for pairs of strings and then goes through the buffer asking if you want to replace any of the first strings of the pairs with the corresponding second string. Since this happens essentially in parallel, you can replace FOO with BAR, BAR with BAZ, BAZ with QUUX and QUUX with FOO in one invocation, without any messing around with temporary strings or abbrevs (as suggested as workarounds in the GNU emacs documentation). (The command Query Exchange is specialised for the case when you want to swap each FOO with a BAR and vice versa.) If you think entering the search and replacement strings in the minibuffer is prone to mistake, you can put them in a buffer and use Multiple Query Replace From Buffer. An essential refactoring tool, I would have thought.

Well, essential once climacs gets Tag Files (the Zmacs name for a collection of buffers or files, whether named in a TAG file, or all the open buffers, or all the files in a system etc.). Then various searching commands can be run over all the files in a Tag File. Which means the ability to suspend and resume a given search, and to visualise pending operations, becomes important.

And then there are the syntax specific searches that climacs should really have – things that allow you to ask for all lists of length 3 with CL:IF as the first element…

But all that is for another day.

Climacs Help

Sunday, May 14th, 2006

Climacs Help

Climacs has quite a few help commands now. The picture above shows Apropos Command (in the lower panel) and Describe Command (in the upper panel).

The interesting thing is that the upper panel was obtained by clicking on the “Kill Line” heading below. And the magic involved?

(present command
         `(command-name :command-table ,command-table)
         :stream out-stream)

when printing and

(define-presentation-to-command-translator describe-command
    (command-name com-describe-command help-table
                  :gesture :select
                  :documentation "Describe command")
    (object)
    (list object))

to make it clickable.

Which just goes to show some of the cool things you get for free if you use CLIM.

The full list of help commands currently available is:

  • Apropos Command (C-h a)
  • Describe Bindings (C-h b)
  • Describe Key Briefly (C-h c)
  • Describe Command (C-h f)
  • Describe Key (C-h k)
  • Where Is (C-h w)

In fact, all these commands are part of ESA, and should therefore be available to any Emacs Style Application written using that framework.