BartC <b...@freeuk.com>:
> Yes, a few scripting languages can do interesting things with switch or
> case statements. Perl for example (where I think it is created out other
> language features, but it looks a regular part of the syntax).
>
> Even Ruby has one. It doesn't do anything 'sexy' with it, but it does
> have this:
>
> case
> when this
> ....
> when that
> ....
> when other
> ...
> end
That's a different topic.
> which is exactly equivalent to if this... elif that... (when the tests
> are ordered), with one difference:
>
> Each test starts with "when", instead of "if" for the first and "elif"
> for subsequent ones. That makes it easier to reorder tests, temporarily
> comment out the first test, copy a test from elsewhere, insert a new
> first test (you get the idea).
That is no different from a chained if/elif.
Scheme has this:
(case (* 2 3)
((2 3 5 7)
'prime)
((1 4 6 8 9)
'composite)
(else
'unknown))
It has something better than C even:
(case (die10)
((1 3 5 7 9)
=> (lambda (n)
n))
(else
=> (lambda (n)
(/ n 2))))
which maps 1, 3, 5, 7 and 9 onto themselves but halves 2, 4, 6, 8 and
10.
As for a chained if/elif, Scheme as "cond:"
(cond
((windy?)
(fly-kite))
((shining? sun)
(go-out))
((raining?)
(play-soccer))
(else
(read-book)))
which also has a "=>" variant:
(cond
((best-selling-book (this-year))
=> (lambda (book)
(read book)))
(else
(play wii pes08)))
Marko
PS What is a "scripting language?"
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