Re: conditionaly setting characteristics

[Chris Maden <crism@xxxxxxx>]

[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
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