emacs lisp as text processing language...

Xah Lee xah at xahlee.org
Mon Oct 29 23:33:54 CET 2007


... continued from previous post.

PS I'm cross-posting this post to perl and python groups because i
find that it being a little know fact that emacs lisp's power in the
area of text processing, are far beyond Perl (or Python).

... i worked as a professional perl programer since 1998. I started to
study elisp as a hobby since 2005. (i started to use emacs daily since
1998) It is only today, while i was studying elisp's file and buffer
related functions, that i realized how elisp can be used as a general
text processing language, and in fact is a dedicated language for this
task, with powers quite beyond Perl (or Python, PHP (Ruby, java, c
etc) etc).

This realization surprised me, because it is well-known that Perl is
the de facto language for text processing, and emacs lisp for this is
almost unknown (outside of elisp developers). The surprise was
exasperated by the fact that Emacs Lisp existed before perl by almost
a decade. (Albeit Emacs Lisp is not suitable for writing general
applications.)

My study about lisp as a text processing tool today, remind me of a
article i read in 2000: “Ilya Regularly Expresses”, of a interview
with Dr Ilya Zakharevich (author of cperl-mode.el and a major
contributor to the Perl language). In the article, he mentioned
something about Perl's lack of text processing primitives that are in
emacs, which i did not fully understand at the time. (i don't know
elisp at the time)

The article is at:
http://www.perl.com/lpt/a/2000/09/ilya.html

Here's the relevant excerpt:
«
Let me also mention that classifying the text handling facilities of
Perl as "extremely agile" gives me the willies. Perl's regular
expressions are indeed more convenient than in other languages.
However, the lack of a lot of key text-processing ingredients makes
Perl solutions for many averagely complicated tasks either extremely
slow, or not easier to maintain than solutions in other languages (and
in some cases both).

I wrote a (heuristic-driven) Perlish syntax parser and transformer in
Emacs Lisp, and though Perl as a language is incomparably friendlier
than Lisps, I would not be even able of thinking about rewriting this
tool in Perl: there are just not enough text-handling primitives
hardwired into Perl. I will need to code all these primitives first.
And having these primitives coded in Perl, the solution would turn out
to be (possibly) hundreds times slower than the built-in Emacs
operations.

My current conjecture on why people classify Perl as an agile text-
handler (in addition to obvious traits of false advertisements) is
that most of the problems to handle are more or less trivial ("system
maintenance"-type problems). For such problems Perl indeed shines. But
between having simple solutions for simple problems and having it
possible to solve complicated problems, there is a principle of having
moderately complicated solutions for moderately complicated problems.
There is no reason for Perl to be not capable of satisfying this
requirement, but currently Perl needs improvement in this regard.
»

  Xah
  xah at xahlee.orghttp://xahlee.org/




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