I'm quoting this out of thread because it really caught my eye and I
wanted to discuss it further and even if people disagree with the
final conclusion, it's a neat trick and example of one of the finer
points of RB being different from other languages.
On Mar 21, 2007, at 5:02 PM, [EMAIL PROTECTED] wrote:
> P.S. You could do this with a Select Case if you really want to, I
> suppose, but it'd be an odd one:
>
> select case True
> case is radiobutton(0).Value
> ...
> case is radiobutton(1).Value
> ...
> end select
>
> Here, you're switching based on the value of "True" by comparing it to
> several object properties. Backwards and weird, but ought to work.
My immediate gut reaction was that this is code taking advantage of
knowledge as to how the compiler works at present and should not be
relied on to work in future.
Then I thought about it a bit more.
Some people swear by the C idiom of
if (99 == myvariable) { }
instead of the more readable
if (myvariable == 99) {}
to avoid the common bug:
if (myvariable = 99) {}
which assigns 99 to myvariable and returns 99 from the expression, so
it has side effects and is always true.
This is of course not an issue in RB because they use = for equality
tests.
So, it felt like generalisation of a common idiom and maybe makes a
degree of sense from that viewpoint.
However, I think it really should be discouraged as an idiom because
the way it works is counter-intuitive to how it reads.
In the radiobutton case it is safe.
An educated programmer translates a select statement into a "match
first true case". It's just an optimal way of writing if x then else
if y then else if z then...
However, that is when matching from variable in the select statement
to expression in the case statement.
My first reaction to 'select case True' was "that will match all the
true cases, gee that's neat". It's not, of course, it's still just
like a chain of if..else if...
I ended up thinking;
1) this is still an interesting technique
2) you should never use it without a comment because some people will
misinterpret it on first reading
3) it would really be neat to have a Select When <expr> but I can't
think of a real-world example, just a feeling prompted by my initial
misreading.
Andy
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