Allen's lambda syntax proposal

P T Withington ptw at pobox.com
Mon Dec 1 08:47:32 PST 2008


On 2008-12-01, at 11:30EST, Mark S. Miller wrote:

> On Mon, Dec 1, 2008 at 7:31 AM, P T Withington <ptw at pobox.com> wrote:
>
>> On 2008-11-30, at 01:30EST, Brendan Eich wrote:
>>
>> // Instead of lambda (a, b, c) { ... }, why not:
>>> { |a, b, c| ... } ?
>>>
>>
>> I would rather have a more literate syntax, lest we degenerate to  
>> where
>> practically any comic book blasphemy is a valid program.
>>
>> (BTW, I'm pretty sure I have that same Byte issue, in a similar  
>> box, with a
>> similar musty smell, _and_ "the blue book".  Back then, worrying  
>> that 'line
>> noise' or the death throes of your modem hanging up would write  
>> code for you
>> was a legitimate concern.  Today, it is just my old eyes that might  
>> gloss
>> over `{||` and wonder why the `var`s in that block are not visible  
>> in the
>> enclosing function...)
>>
>
> Since it's a lambda, the 'var's will be visible in the enclosing  
> function.

Eh?  So:

function () {
   var foo = 42;
   {|| var foo = 3; }
   return foo;
}

and:

function () {
   var foo = 42;
   { var foo = 3; }
   return foo;
}

Give the same answer?

> The point of having a very compact syntax for lambda is too make it  
> pleasant
> to write control abstractions, as one does casually in Smalltalk.  
> With the
> verbose "lambda" spelling, people will avoid those, or invent macro  
> systems
> (as Scheme programmers do) mostly so they can avoid seeing all those  
> extra
> "lambda" letters in the code.
>
> Think of lambdas as blocks plus a bit more, rather than function  
> minus a
> bit. Viewed this way, their block-like syntax is a virtue.

I agree with the goal of compactness.  I just don't like it to be too  
compact.  Call me a curmudgeon.  I don't like that `not` is spelt `!`  
or that it is so easy to make a one-letter misspelling of `eql` and  
end up with `setq` either.


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