Hi, Paul,
Several other folks have given good, comprehensive explanations. I
might add a simple trick; read
any [...]
as if it were a synonym for
first_established_value_in [...]
where "established" means something other than none or false. It's
saying "try these in this order, and quit as soon as you find one"
(in a loose sort of way).
REBOL allows you to make puns in logic-oriented expressions; none is
considered to be false, and everything else (other than false and its
synonyms no and off) is considered to be true. As a consequence,
foo: any [ gorp bletch quux flarp "default"]
can be used as short-hand for the imperative code
either found? gorp and gorp [ foo: gorp ][
either found? bletch and bletch [ foo: bletch ][
either found? quux and quux [ foo: quux ][
either found? flarp and flarp [ foo: flarp ][
foo: "default"
] ] ] ]
For example, if I have a Great Big Hairy Database of contact and
address data (and some suitable function definitions ;-), I could
write
your-address: any [
your-home-address
your-work-address
your-parents-address
general-delivery-to-your-home-town
"no address on file"
]
-jn-
