Reuse 'do' keyword instead of hash sign (#)

[Sam Pullara]

A long time ago I proposed that we actually use new, but that doesn't make that much sense now. Mine was more syntactic sugar for SAMs rather than lambdas:

new (x) { x + 1 }

list.filter( new (t) { t.length > 3}).map(new (t) { t.barCount}).max()

The nice thing about it is that it looked a lot like an anonymous inner class creation with a lot of type inference.

Sam

On Jun 20, 2011, at 9:51 AM, Dan Smith wrote:

> Generally speaking, you're right -- keywords are for statements.  But there is one exception: 'new'; arguably, lambda expressions and class instance creations fall into a similar class of expressions.
> 
> (As a slight digression, I think the 'if' vs. '?' parallel is useful to consider:
> 
> if (cond) statement1; else statement2;
> cond ? expr1 : expr2
> 
> Some points:
> - The statement form uses keywords; the expression form uses obscure operator characters.
> - Programmers seem to be comfortable understanding which to use in which contexts.
> - The expression form is _not_ enclosed in delimiters, and requires some "lookahead" to mentally process.
> 
> Further generalizations depend on how you feel about '?:'.  Perhaps it's a good example to model lambda expressions after.  Or perhaps it's a poorly-designed feature that scares too many beginners away, and we shouldn't use it as a model.)
> 
> —Dan
> 
> On Jun 20, 2011, at 12:11 AM, Stephen Colebourne wrote:
> 
>> No from me too.
>> (Keywords introduce statements in Java, not expressions.)
>> Stephen
>> 
>> 2011/6/18 Marcin Wiśnicki <mwisnicki at gmail.com>:
>>> This is a repost from 2010/8 since apparently now syntax is up for
>>> discussion but wasn't back then.
>>> Also I didn't like any proposal from "Syntax poll" thread ;(
>>> 
>>> You can call it "do" syntax ;)
>>> I didn't have the time to think it thoroughly or follow recent java7/8
>>> developments but here it goes:
>>> 
>>> Would it be possible to change the clumsy '#' operator to 'do' keyword ?
>>> I.e.:
>>> 
>>> do()(5)
>>> do(){return 5;}
>>> do(int x, int y) { if (x>y) return x; else return y; }
>>> button.onClick(do(Event e) { println("button clicked"); });
>>> 
>>> "strawman" syntax example:
>>> 
>>> list.filter( #(Foo t)(t.length() > 3) )
>>>     .map( #(Foo t)(t.barCount) )
>>>     .max();
>>> 
>>> becomes:
>>> 
>>> list.filter( do(Foo t)(t.length() > 3) )
>>>     .map( do(Foo t)(t.barCount) )
>>>     .max();
>>> 
>>> I find it more readable; using special characters feels a bit
>>> like perl (noisy), especially when combining multiple lambdas.
>>> It even makes sense if you parse it as english.
>>> 
>>> Don't know what to do with anonymous function type but it could remain as '#'.
>>> 
>>> Pros:
>>> - more readable
>>> - makes sense
>>> - like '#' needs only 1-lookahead to disambiguate from do-while '(' vs '{' [1]
>>> - did I mention it's more readable ?
>>> 
>>> Cons:
>>> - none (that I could think of)
>>> 
>>> [1] Automatic Resource Management from Coins wanted to use 'do' but I
>>> see they have switched to 'try' so no problem there.
>>> 
>>> PS. Please CC me when responding, thanks.
>>> 
>>> 
>> 
> 
>