[PEAK] "Coherence" - a Trellis-like language w/error handling

[Sergey Schetinin]

On Sat, Apr 25, 2009 at 12:31, Sergey Schetinin <maluke at gmail.com> wrote:
>    @end.filter_assign
>    def end_assign(self, end):
>        self.start += end - self.end
>        return end

I wonder what got into me implementing it like that, obviously it
should be "self.start = end - self.length".

In fact I already have a monkeypatch that allowed me to immediately
write and test this:

class Task1(Component):
    attrs(name='task1', start=1, length=2)
    @compute
    def end(self):
        return self.start + self.length

    @end.writer
    def end_write(self, end):
        self.start = end - self.length

It works well for the trivial cases but writer is implemented rather
naively so this wouldn't work:

t1 = Task()
@trellis.atomically
def change():
    t1.end = 20
    t1.length = 10

it results in (t1.start, t1.end) == (18,28)

However if writer is implemented as a Cell that is scheduled on
assignment it would handle that no problem.