Speaking as a "non-programmer", but one who writes quite a bit of XSLT:
At 07:41 AM 12/27/01, Andrew wrote:
1. Is there ever a good time to use a for-each? From reading this list for
a while these seem to be the root of most problems and are very rarely
included in any solutions... are they really necessary? (Ive read in places
they were intended to make the language easier to learn for beginners!)
Yes, there is. Even the most die-hard of us who disparage it will admit
this, I'll warrant. When used properly, it can make stylesheets simpler to
read, write and maintain. It also provides useful workarounds in edge cases
(to momentarily change the context node inside a template, for example).
When used improperly, it soon has the opposite effect. When it is
improperly used it is almost always because the stylesheet designer is
unaware of or still uncomfortable with the available alternatives.
Whether they are "necessary" depends on what you mean by "necessary".
I have never seen it argued that it was "intended" to make the language
easier for beginners, and personally would doubt this. (If you or any
reader can quote this argument directly, with any evidence for it, it might
give somebody something to rain on. :-) I have seen it argued that it does
this -- but personally I think this argument is specious, not too unlike
saying that a cake mix is a good way to start learning to bake. It is not
that you can't learn XSLT that way -- indeed, some proponents of this point
of view certainly know the language and are good teachers, tuned in to how
people learn. But I would argue that experience shows that xsl:for-each is
most dangerous in the hands of a beginner who does not have the advantage
of direct guidance by an experienced practitioner. It might provide an easy
way in if you are so guided -- for about an hour or so. Beyond that, they
better take you to templates or you'll get in trouble. (My $0.02!)
But all this is just generalization: specific cases are strongly affected
by the experience, background, expectations, temperament and style of the
learner as well as the nature of the data, the requirements for the
transformation, and other unknowables such as whether you're ever going to
write a second stylesheet, and what *that* one will have to do.
2. If a variable cannot be changed after it has been assigned, why call it
a variable? Ive read the reasoning behind this, and yes strictly it is a
variable, but a more appropriate name would make sense.
It makes sense if (a) you know the term "variable" from algebra, not Perl
(the extremely naive case), or (b) you are aware that technical
terminologies are by nature somewhat slippery when you try to carry them
across domains (the very sophisticated case) and don't set too much store
by *any* name.
I remember in ninth grade feeling that the BASIC statement "x=x+1" made no
sense, but I was willing to bend my brain to live with it. :-) (I later
learned to make the distinction between assigning a value, and claiming an
equivalence. This distinction is actually quite useful in the study of
human rhetorics -- and maybe in understanding XSLT.)
The above makes XSLT non-intuitive, and therefore harder to learn. Is there
another language where you cannot change the value of a variable?
I'd submit that there are cases where "harder to learn" also means "better
to learn". Paradigm shifts and all that. I'm not arguing that this is one
of those cases. As to your question, that depends on what you mean by
"variable" -- a predefined thing (let's see the definition), or whatever
the language in question calls a "variable"? I believe there are languages
that have something named a "variable" with properties similar to the thing
XSLT calls a variable.
Thanks for your comments, Andrew.
Regards,
Wendell
======================================================================
Wendell Piez mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc. http://www.mulberrytech.com
17 West Jefferson Street Direct Phone: 301/315-9635
Suite 207 Phone: 301/315-9631
Rockville, MD 20850 Fax: 301/315-8285
----------------------------------------------------------------------
Mulberry Technologies: A Consultancy Specializing in SGML and XML
======================================================================
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list