Ted Leung on the air
Ted Leung on the air: Open Source, Java, Python, and ...
Sat, 10 May 2003
macros vs keyword messages
It's great when you actually learn something new, and I seem to do that quite frequently in the weblog world. Here's today's:

Patrick Logan, who I remember from comp.lang.dylan days, had this to say about syntax extension:

While Smalltalk doesn't have syntax macros like Lisp, Smalltalk *does* have simpler block syntax and keyword arguments.

The effect is that new keyword messages can take block closures, which essentially delay evaluation until the method behind the message decides to evaluate them, and the message send looks an awful lot like new syntax, very clean.

Many uses of macros in Lisp, frankly, are simply created to hide the appearance of the lambda keyword. Of course there are more "legitimate" uses of macros, but these are less common.

This use of keyword messages and closures is really interesting. In Chapter 8 of On Lisp, Graham lists 6 reasons to use macros. Delaying or altering evaluation is an aspect of the first 4 reasons. Reason 5 involves using the calling environment, which you very rarely want to do, reason 6 involves using a new lexical environment, which you also rarely want to do, and reason 7 is inlining which is a performance annotation.

I'd be curious to see some examples of this type of Smalltalk code.

[00:12] | [computers/programming/lisp] | # | TB | F | G | 3 Comments | Other blogs commenting on this post
You can subscribe to an RSS feed of the comments for this blog: RSS Feed for comments

Add a comment here:

You can use some HTML tags in the comment text:
To insert a URI, just type it -- no need to write an anchor tag.
Allowable html tags are: <a href>, <em>, <i>, <b>, <blockquote>, <br/>, <p>, <code>, <pre>, <cite>, <sub> and <sup>.

You can also use some Wiki style:
URI => [uri title]
<em> => _emphasized text_
<b> => *bold text*
Ordered list => consecutive lines starting spaces and an asterisk

Name:


E-mail:


URL:


Comment:


Remember my info?


twl JPG

About

Ted Leung FOAF Explorer

I work at the Open Source Applications Foundation (OSAF).
The opinions expressed here are entirely my own, not those of my employer.

Creative Commons License
This work is licensed under a Creative Commons License.

Now available!
Professional XML Development with Apache Tools : Xerces, Xalan, FOP, Cocoon, Axis, Xindice
Technorati Profile
PGP Key Fingerprint
My del.icio.us Bookmarks
My Flickr Photos


Syndicate
RSS 2.0 xml GIF
Comments (RSS 2.0) xml GIF
Atom 0.3 feed
Feedburner'ed RSS feed

< May 2003 >
SuMoTuWeThFrSa
     1 2 3
4 5 6 7 8 910
11121314151617
18192021222324
25262728293031

Archives
2006
2005
2004
2003

Articles
Macintosh Tips and Tricks

Search
Lucene
Blogs nearby
geourl PNG

Categories
/ (1567)
  books/ (33)
  computers/ (62)
    hardware/ (15)
    internet/ (58)
      mail/ (11)
      microcontent/ (58)
      weblogs/ (174)
        pyblosxom/ (36)
      www/ (25)
    open_source/ (145)
      asf/ (53)
      osaf/ (32)
        chandler/ (35)
        cosmo/ (1)
    operating_systems/ (16)
      linux/ (9)
        debian/ (15)
        ubuntu/ (2)
      macosx/ (101)
        tips/ (25)
      windows_xp/ (4)
    programming/ (156)
      clr/ (1)
      dotnet/ (13)
      java/ (71)
        eclipse/ (22)
      lisp/ (34)
      python/ (86)
      smalltalk/ (4)
      xml/ (18)
    research/ (1)
    security/ (4)
    wireless/ (1)
  culture/ (10)
    film/ (8)
    music/ (6)
  education/ (13)
  family/ (17)
  gadgets/ (24)
  misc/ (47)
  people/ (18)
  photography/ (25)
    pictures/ (12)
  places/ (3)
    us/ (0)
      wa/ (2)
        bainbridge_island/ (17)
        seattle/ (13)
  skating/ (6)
  society/ (20)



[Valid RSS]

del.icio.us linkblog

www.flickr.com

Blogroll

java.blogs
Listed on BlogShares

Locations of visitors to this page
Where are visitors to this page?


pyblosxom GIF