Subject: Re: conditionaly setting characteristics From: Chris Maden <crism@xxxxxxx> Date: Tue, 24 Feb 1998 13:34:12 -0500 |
[Richard Light] > This can give rise to some strange logic - I don't think that you > can test for (attribute-string) returning #t as you do, since it > only returns #f or a string. I thought someone else would comment on this, but... Clause 8.2.2 of DSSSL says: "All values count as true in [a conditional test] except for #f." This leads to overloaded, but natural appearing, syntax like (if foo foo "") where foo is the result of (attribute-string ...) or some other something-or-#f procedure. This is a dangerous habit to get into, though, because nodal procedures often return an empty nodelist, not #f, if the target isn't found, necessitating (if (node-list-empty? foo) some-default foo) -Chris -- <!NOTATION SGML.Geek PUBLIC "-//Anonymous//NOTATION SGML Geek//EN"> <!ENTITY crism PUBLIC "-//O'Reilly//NONSGML Christopher R. Maden//EN" "<URL>http://www.oreilly.com/people/staff/crism/ <TEL>+1.617.499.7487 <USMAIL>90 Sherman Street, Cambridge, MA 02140 USA" NDATA SGML.Geek> DSSSList info and archive: http://www.mulberrytech.com/dsssl/dssslist
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