Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: Joshua Cranmer <Pidgeot18@verizon.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: new Java lambda syntax
Date: Sun, 11 Sep 2011 17:07:56 -0500
Organization: A noiseless patient Spider
Lines: 36
Message-ID: <j4jbgt$i60$1@dont-email.me>
References: <j4b80q$u30$1@dont-email.me> <alpine.DEB.2.00.1109101445260.18967@urchin.earth.li> <llbsj8-b59.ln1@news.simpsonst.f2s.com> <alpine.DEB.2.00.1109111255530.13018@urchin.earth.li> <9j3vj8-aqe.ln1@news.simpsonst.f2s.com> <j4item$o69$1@news.albasani.net> <tsdvj8-vbg.ln1@news.simpsonst.f2s.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Sun, 11 Sep 2011 22:08:30 +0000 (UTC)
Injection-Info: mx04.eternal-september.org; posting-host="WpcHJSul77m+zlbR9GVqkA"; logging-data="18624"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+RekEB27pRLJrHvyVDqEI8+/XVoa4i5d8="
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:6.0.2) Gecko/20110902 Thunderbird/6.0.2
In-Reply-To: <tsdvj8-vbg.ln1@news.simpsonst.f2s.com>
Cancel-Lock: sha1:G/0jftyZayz897FRuial42KRWMg=
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:7830

On 9/11/2011 2:14 PM, Steven Simpson wrote:
> On 11/09/11 19:08, BGB wrote:
>> I would have also liked to see lexical variable capture.
>> FFS, I added this (along with closures) to a C compiler before, can't
>> be too hard
>
> At this stage, I don't think the issue is how, but whether/when to
> permit it.

There are other issues like does it capture the value or does it use the 
same variable. e.g., what would this produce:

List<Runnable> runners = new LinkedList<Runnable>();
for (int i = 0; i < 10; i++) {
   runners.add(() => { System.out.println("Value of i is " + i); });
}
for (Runnable r : runners) {
   r.run();
}

Should you see 0..9 or 10 repeated 10 times?

> For invocations, having to type obj.run() instead of obj() is hardly
> onerous. Plus, invocations will be much rarer than lambda declarations.
> Also note that the invocation site is unaware of whether the object is a
> lambda.

Also, note the (slight) benefits of explicitly saying what you are 
doing. You might choose, reasonably, to call the callback parameter for 
an asyncForEach function `block', at which point the functional call 
specification becomes block(value), which can be visually ambiguous as 
to what it's doing. block.call(value) is clearer, on the other hand.

-- 
Beware of bugs in the above code; I have only proved it correct, not 
tried it. -- Donald E. Knuth