All the responses given by Eliot and Liam respect Clean Code[1] best
practises. Many principles must be respected if you expect your code may
evolve :
* DRY : Don't Repeat Yourself ; sometime in opposition with Single
Responsability principle
* YAGNI : You Ain't Gonna Need It
* SOLID, with only some of them applicable to XSLT :
o S : Single Responsability Principle: There must have no more
than One reason to modifiy this piece of code
o O : Open Close Principle: Open to Extension, Closed to Modification
All of these principles try to avoid use of global variables, even if
it's not clearly written in the details of pirinciples. As Mike says,
Evil is in the detail, but Evil is also in global variables.
HTH,
Christophe
[1] : clean Code, Bob Martin, Pearson Addison-Wesley, 2009
Le 18/06/2021 à 20:28, Eliot Kimber ekimber(_at_)contrext(_dot_)com a écrit :
If I was given a style sheet with a function that used a global
variable I would immediately rewrite the function to take that
variable as a parameter.
Cheers,
E.
--
Eliot Kimber
http://contrext.com
*From: *"Liam R. E. Quin liam(_at_)fromoldbooks(_dot_)org"
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>
*Reply-To: *<xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com>
*Date: *Friday, June 18, 2021 at 12:56 PM
*To: *<xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com>
*Subject: *Re: [xsl] user-defined XSLT functions and stylesheet variables?
On Fri, 2021-06-18 at 17:42 +0000, David Birnbaum djbpitt(_at_)gmail(_dot_)com
<mailto:djbpitt(_at_)gmail(_dot_)com>
wrote:
Dear XSLT-list,
Is there agreement about Best Practice with respect to using
stylesheet
(global) variables inside user-defined functions?
Tommie once gave a talk about best practice considered hamrful... :)
You've identified some of the issues, but for me the most important
ones are this:
(1) locality of reference: can i understand thefunction without having
to look elsewhere?
(2) maintainability: how easy will it be to fix problems in this
function in the future, or for someone else to change it, perhaps to
workslightly differently on edge cases. Assume they are in a hurry.
(3) can i take the function and reuse it in another stylesheet later?
Overall the use of global variables is likely to be an impediment to
each of these.
Liam
--
Liam Quin, https://www.delightfulcomputing.com/
<https://www.delightfulcomputing.com/>
Available for XML/Document/Information Architecture/XSLT/
XSL/XQuery/Web/Text Processing/A11Y training, work & consulting.
Barefoot Web-slave, antique illustrations: http://www.fromoldbooks.org
<http://www.fromoldbooks.org>
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