Re: Re: Strange type error

Thanks all. 

Bonus points for any 

On Friday, 8 May 2015 03:21:25 UTC+2, Andrew Phillips wrote:
>
> Hi Toby
>
> > So, at the time the compiler needs to decide which part of the code 
> constitutes an anonymous function, it cannot 
> > yet take into account, what type is required. It needs to go by syntax 
> only, and that leaves few options besides 
> > limiting it to simple expressions.
>
> Just to add to Oliver's answer: it's not explicitly stated in the spec 
> (6.23) in this way, but what works for me as a guideline is to regard the 
> scope of the anonymous function that the compiler creates as extending to 
> the *innermost enclosing expression* containing the '_' placeholder 
> character.
>
> So _ + _* _ is desugared to (x, y, z) => x + y * z because the innermost 
> enclosing expression is the whole expression. In the case of _ + (_ * _), 
> however, the innermost enclosing expression for the latter two placeholders 
> is (_ * _), so the compiler first expands that to an anonymous function _ + 
> ((y, z) => y * z) and then does that again for the first placeholder.
>
> This also explains why e.g.
>
> List(1, 2).map { i => println("Hi"); i + 1 } and
> List(1, 2).map { println("Hi"); _ + 1 }
>
> behave differently [1]: the innermost enclosing expression for the 
> placeholder in the second statement is _ + 1, so the result is effectively
>
> List(1, 2).map { println("Hi"); i => i + 1 }
>
> Regards
>
> ap
>
> [1] http://scalapuzzlers.com/#pzzlr-001
>

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