::= is an operator for newSlot() which creates a setSlot which takes
an argument and sets the value on the slot. While that doesn't make a
lot of sense, consider this:
foo := 42
Creates a single slot, "foo" with the value 42.
Consider:
foo ::= 42
Creates a slot called "foo" with the value 42, and creates a "setFoo"
which takes a single argument, the value to update the "foo" slot with.
The difference between @ and @@ is that @ returns a Future and fires
off a coro into the "background". Consider:
blurgle := @bar
whatever bar is will be run in a coro and a future will be immediately
returned to blurgle. If you access blurgle (lookup that slot) before
bar is done running, the coro will pause and wait for bar to finish
before returning the result.
If you run:
blurgle := @@bar
What will happen is blurgle will be nil immediately, and when you
access blurgle you'll get nil until bar is finished running then
you'll get the value of whatever bar evaluated to.
I hope this is clear.
On 21-Apr-09, at 10:36 AM, HowardP wrote:
>
>
> HI all,
>
> I've read most of the docs on Io, but am still unclear about these
> two items:
>
>
> What's the difference really between
>
> ::=
>
> and
>
> :=
>
> The ' := ' is obvious, ' ::= ' not so.
>
>
> And what's the difference between the coroutine syntax of
>
> @thing
>
> and
>
> @@thing
>
>
> thank you for the assistance,
>
>
> GO IO !
>
>
>
Regards,
Jeremy Tregunna
jeremy.tregunna@...
