HaloO,
Dave Whipp wrote:
TSa wrote:
class Length
{
has Num $.mm is rw = 0;
method inch
{
yield $inch = $.mm * 25.4;
self.mm = $inch / 25.4;
}
}
Would you regard that as elegant?
That looks functionally incorrect to my eyes: if the caller resumes at
the time of the "yield" statement, and immediately assigns a new value
to the "mm" attribute, then there is a race between the two updates to
"mm".
Why two assignments? $.mm is assigned only after resumption. From the
outside the ResumeProxy is used as '$obj.inch = 17' for assignment that
resumes the accessor and as 'say $obj.inch' as rvalue access that
garbage collects the invocation. The idea is that yield is a pseudo-
declarator. That is the above means
method inch
{
my $inch = $.mm * 25.4;
yield $inch;
self.mm = $inch / 25.4;
}
and might need a 'is rw' trait for better documentation.
Or did you mean
my $obj = Length.new;
$obj.inch = 17;
$obj.mm = 100;
where I think the sequence of events is
1) the invocation of .inch
2) the yield of a ResumeProxy
3) the call of infix:<=> with 17
4) the resumption of the .inch invocation from 1
5) the return of that assignment
6) now the sequence is complete and the next
assignment just overwrites the one from 1-5
Regards, TSa.
--
"The unavoidable price of reliability is simplicity" -- C.A.R. Hoare
"Simplicity does not precede complexity, but follows it." -- A.J. Perlis
1 + 2 + 3 + 4 + ... = -1/12 -- Srinivasa Ramanujan
