Still not right. I screwed up the scoping of the "balance" variable.
Another correction coming soon.
On Thu, Jan 17, 2013 at 9:17 AM, Mark S. Miller <erig...@google.com> wrote:
> On Thu, Jan 17, 2013 at 9:13 AM, Andreas Rossberg <rossb...@google.com> wrote:
>> Hm, I'm afraid I don't fully understand that example. There seems to
>> be a missing closing brace for the constructor, and I don't know what
>> the free occurrences of 'balance' are referring to. Also, the second
>> line of the deposit function seems to be missing in the expansion.
>
> You're right. I also forgot a "new". Corrected I think:
>
>
> class Purse {
> constructor(private balance) {}
> getBalance() { return balance; }
> makePurse() { return new Purse(0); }
> deposit(amount, srcPurse) {
> private(srcPurse).balance -= amount;
> balance += amount;
> }
> }
>
> expansion
>
> let Purse = (function() {
> let amp = WeakMap();
> function Purse(balance) {
> amp.set(this, Object.seal({
> get balance() { return balance; },
> set balance(newBalance) { balance = newBalance; }
> }));
> }
> Purse.prototype = {
> getBalance: function() { return balance; },
> makePurse: function() { return new Purse(0); },
> deposit: function(amount, srcPurse) {
> amp.get(srcPurse).balance -= amount;
> balance += amount;
> }
> }
> return Purse;
> })();
>
>
> Please let me know if anything else remains mysterious or looks wrong.
>
> --
> Cheers,
> --MarkM
--
Cheers,
--MarkM
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