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Postings from February 2002
On Wed, Feb 27, 2002 at 10:32:24AM -0600, Garrett Goebel wrote:
>
> Why does C<when>'s EXPR pay attention to the topicalizer regardless of
> associated variable?
>
> Why introduce the special case? Especially when consistency and
> simplification seem to be a strong undercurrent in Perl6? I'm curious what
> the reasoning behind the special case is. I don't see what it gives us...
> beside one more thing to remember. What would be a use case that illustrates
> the need for the special case? And is the special case the common one?
>
> $_ = 'foo';
> given 'bar' -> $f {
> if /foo/ {print}; # true, prints 'foo'
> when /bar/ {print}; # true, prints 'foo'
> when /bar/ -> $g {print}; # true, prints what? 'foo'
> }
Why? Because it's oh-so dwim. Think about it, if you've just typed a
given $x { ...
or
given $x -> $y { ...
you know for a fact that you're going to want every C<when> to
compare against the $_ or $y. Why force people to type:
when $y =~ /a/ {...}
when $y =~ /b/ {...}
...
when you already know what they mean? And yes, it's the common case. How
many times do you think you'll have a switch statement and want the case
to compare against some value external to the switch?
$_ = 'foo';
given 'bar' -> $y {
when /a/ {...}
}
It's counterintuitive for this to translate to "When that foo value
matches /a/ then take an action." If you'd meant that, it would make
alot more sense to do:
given 'foo' {
when /a/ {...}
}
Allison