2.7.7 -> 2.8.0 changes

Anything creating an Array or calling something that creates an Array now needs a manifest. Just replace [A,B] with [A,B : Manifest], or add (implicit man: Manifest[B]).   By the way, 2.8's Range is strict.

On Tue, Apr 6, 2010 at 2:57 PM, Russel Winder <russel@russel.org.uk> wrote:

Hi,

I found the following somewhere on the Web and it seems to do the right
thing (sort of) under 2.7.7.  However under 2.8.0 I get an error
message.  Is it something trivially simple I am missing?

       class Mapper[A,B] ( data : List[A] , function : A => B ) {
         val pmap = {
           val buffer = new Array[B] ( data.length )
           // Ranges are lazy but we need strict so the .toList
           val mappers = for ( index <- ( 0 until data.length ).toList ) yield
               Futures.future { buffer ( index ) = function ( data ( index ) ) }
           for ( mapper <- mappers ) mapper ( )
           buffer
         }
       }


scalac -optimise Pi_Scala_ParMap.scala
Pi_Scala_ParMap.scala:11: error: cannot find class manifest for element
type B
   val buffer = new Array[B] ( data.length )
                ^
Pi_Scala_ParMap.scala:15: error: mapper of type Nothing does not take
parameters
   for ( mapper <- mappers ) mapper ( )
                                    ^
two errors found


--
Russel.
=============================================================================
Dr Russel Winder      t: +44 20 7585 2200   voip: 3Arussel [dot] winder [at] ekiga [dot] net" rel="nofollow">sip:russel.winder@ekiga.net
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel@russel.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder

--
Daniel C. Sobral

I travel to the future all the time.

On Tue, 06 Apr 2010 15:40:26 -0300, Daniel Sobral wrote:

> [A,B : Manifest]

Interesting - I haven't seen this before . What is is called, and does it
do?

On Wed, Apr 7, 2010 at 6:53 AM, Sam Stainsby
wrote:
> On Tue, 06 Apr 2010 15:40:26 -0300, Daniel Sobral wrote:
>> [A,B : Manifest]
> Interesting - I haven't seen this before . What is is called, and does it
> do?

It's called a context bound. The array SID talks a bit about it.

Best,
Ismael

It's equivalent to my alternate solution:
replace [A,B] with [A,B : Manifest], or add (implicit man: Manifest[B])

On Wed, Apr 7, 2010 at 2:53 AM, Sam Stainsby <sam@sustainablesoftware.com.au> wrote:

On Tue, 06 Apr 2010 15:40:26 -0300, Daniel Sobral wrote:

> [A,B : Manifest]


Interesting - I haven't seen this before . What is is called, and does it
do?

--
Daniel C. Sobral

I travel to the future all the time.

On Wed, 07 Apr 2010 08:33:11 -0300, Daniel Sobral wrote:

> It's equivalent to my alternate solution:
>
> replace [A,B] with [A,B : Manifest], *or add (implicit man:
> Manifest[B])*

Except in the second case you have 'man', which can be accessed within
the class.

The manifest can also be accessed when using context bounds - via implicitly[B] - as defined in Predef

On 7 April 2010 12:47, Sam Stainsby <sam@sustainablesoftware.com.au> wrote:

On Wed, 07 Apr 2010 08:33:11 -0300, Daniel Sobral wrote:

> It's equivalent to my alternate solution:
>
> replace [A,B] with [A,B : Manifest], *or add (implicit man:
> Manifest[B])*

Except in the second case you have 'man', which can be accessed within
the class.

--
Kevin Wright

mail/google talk: kev.lee.wright@googlemail.com
wave: kev.lee.wright@googlewave.com
skype: kev.lee.wright
twitter: @thecoda

(*Make that implicitly[Manifest[B]] )

2010/4/7 Kevin Wright <kev.lee.wright@googlemail.com>

The manifest can also be accessed when using context bounds - via implicitly[B] - as defined in Predef

On 7 April 2010 12:47, Sam Stainsby <sam@sustainablesoftware.com.au> wrote:

On Wed, 07 Apr 2010 08:33:11 -0300, Daniel Sobral wrote:

> It's equivalent to my alternate solution:
>
> replace [A,B] with [A,B : Manifest], *or add (implicit man:
> Manifest[B])*

Except in the second case you have 'man', which can be accessed within
the class.

--
Kevin Wright

mail/google talk: kev.lee.wright@googlemail.com
wave: kev.lee.wright@googlewave.com
skype: kev.lee.wright
twitter: @thecoda

yeah, that too :)

On 7 April 2010 13:20, Dimitris Andreou <jim.andreou@gmail.com> wrote:

(*Make that implicitly[Manifest[B]] )

2010/4/7 Kevin Wright <kev.lee.wright@googlemail.com>

The manifest can also be accessed when using context bounds - via implicitly[B] - as defined in Predef

On 7 April 2010 12:47, Sam Stainsby <sam@sustainablesoftware.com.au> wrote:

On Wed, 07 Apr 2010 08:33:11 -0300, Daniel Sobral wrote:

> It's equivalent to my alternate solution:
>
> replace [A,B] with [A,B : Manifest], *or add (implicit man:
> Manifest[B])*

Except in the second case you have 'man', which can be accessed within
the class.

--
Kevin Wright

mail/google talk: kev.lee.wright@googlemail.com
wave: kev.lee.wright@googlewave.com
skype: kev.lee.wright
twitter: @thecoda

--
Kevin Wright

mail/google talk: kev.lee.wright@googlemail.com
wave: kev.lee.wright@googlewave.com
skype: kev.lee.wright
twitter: @thecoda

>> (*Make that implicitly[Manifest[B]] )

Nice! That should reduce some clutter in my code.