On Wed, Aug 17, 2005 at 01:56:35PM +1000, Adam Kennedy wrote:
: >: If not a special form, should this work?
: >: my $pi is constant;
: >: $pi = 3;
: >That could be made to work by defining constant to mean you can assign
: >to it if it's undefined. But then it gets a little harder to reason
: >about it if $pi can later become undefined. I suppose we could
: >disallow undefine($pi) though.
: Which would basically throw away compile-time optimizations relating to
: constants wouldn't it?
You could still reason about it if you can determine what the initial
value is going to be. But certainly that's not a guarantee, which
is one of the reasons we're now calling this write/bind-once behavior
"readonly" and moving true constants to a separate declarator:
my $pi is readonly;
$pi = 3;
constant $pi = 3;
constant Num pi = 3;
or if you like, even
constant π = 3;