sort on two keys

Re: sort on two keys

Mohamed Bana-6 wrote:
*

> 
> Hi All,
> 
> What would be the equivalent of the C# program below?
> 
> var counts = new Dictionary<string, int>();
> 
> var sortedDict =
>   from entry in counts
>   orderby entry.Value descending, entry.Key ascending
>   select entry;
> 
> that is, sort by max no. then alphabetically.
> 
> —Mohamed
> 
> 

I hope I got it right...

val m = Map("one"->1,"once"->1,"two"->2,"twice"->2,"double"->2,"three"->3)
m.toList.sort((x,y) => if (x._2 == y._2) x._1 < y._1 else x._2 > y._2)
//--> res1: List[(java.lang.String, Int)] = List((three,3), (double,2),
(twice,2), (two,2), (once,1), (one,1))

Cheers,
Daniel

--

-- 
View this message in context: http://old.nabble.com/-scala--sort-on-two-keys-tp27522069p27523939.html
Sent from the Scala mailing list archive at Nabble.com.

Very weird error

Re: Very weird error

Re: Very weird error

Adding ARM to Scala's standard library

Probably anybody that has written something that needs to be closed after use 
has written something like

object With
{
   def closeable[C <: java.io.Closeable,R](c: C)
                                          (f: C => R): R =
   {
     try {
       f(c)
     }
     finally {
       try {
        c.close()
       }
       catch {
         // #### Log this, but how?
         case e =>
       }
     }
   }
}

Then it would be used as

With.closeable(new ByteArrayOutputStream(1024)) { os =>
   ...
}

This looks like something that would do well in Scala's standard library.

One question is how to deal with the logger for the standard library.  I use 
slf4j in my projects but not everybody does.  I think if this code is in the 
standard library then it must provide a way to have the exception from #close() 
be logged with the logger of choice.  The With object could become an abstract 
class with an abstract logging method than projects would instantiate their own 
concrete class with their logger of choice.

abstract class With
{
   protected def logCloseException(t: Throwable): Unit
}

object MyWith
   extends With
{
   override protected def logCloseException(t: Throwable): Unit = ...
}

BTW, the reason not to use structural subtyping is performance and it doesn't 
work with Oracle's java.sql.ResultSet subclass:

   def with_closeable[T <: { def close(): Unit }]

   java.lang.IllegalAccessException: Class DatabaseCopy$ can not
   access a member of class oracle.jdbc.driver.OracleResultSetImpl
   with modifiers "public synchronized"
   at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
   at java.lang.reflect.Method.invoke(Method.java:588)

Blair

Re: Adding ARM to Scala's standard library

On Mon, Feb 08, 2010 at 08:06:41AM -0800, Blair Zajac wrote:
> This looks like something that would do well in Scala's standard 
> library.

I thought you were here the last few months.

> BTW, the reason not to use structural subtyping is performance and it 
> doesn't work with Oracle's java.sql.ResultSet subclass:

http://lampsvn.epfl.ch/trac/scala/ticket/2318
"Structural method is dispatched on non-public member when overriding public member"

--

-- 
Paul Phillips      | Atheists dig the best foxholes.
In Theory          | 
Empiricist         | 
slap pi uphill!    |----------* http://www.improving.org/paulp/ *----------

Re: Adding ARM to Scala's standard library

On Feb 8, 2010, at 8:29 AM, Paul Phillips wrote:

> On Mon, Feb 08, 2010 at 08:06:41AM -0800, Blair Zajac wrote:
>> This looks like something that would do well in Scala's standard 
>> library.
> 
> I thought you were here the last few months.

I've got 19,000 unread messages in my Scala mailbox and not enough time to keep up on everything :(

I found Josh's thread mentioning scalax.io, but the source repository at hg.scalaforge.org is down.

Is the most current discussion at
http://groups.google.com/group/scala-incubator/web/arm-questions ?

> 
>> BTW, the reason not to use structural subtyping is performance and it 
>> doesn't work with Oracle's java.sql.ResultSet subclass:
> 
> http://lampsvn.epfl.ch/trac/scala/ticket/2318
> "Structural method is dispatched on non-public member when overriding public member"

Thanks.

Blair

Re: Adding ARM to Scala's standard library

Re: Adding ARM to Scala's standard library

Josh,

Thanks, I'll take a look.

BTW, with my sample "With" object, I later realized that different projects will 
want different behavior when close() throws an exception, some will want to 
silence it and others will want to propagate it if the try block didn't throw an 
exception.  So I would need a With.closeable() and With.closeableQuietly().

Blair

Josh Suereth wrote:
*

> Blair, there's actually a project on github here:
> 
> http://github.com/jsuereth/scala-arm
> 
> I need to get back into it and tweak the thing.  I think my experiment 
> with "leaky monads" is failed, but let me know what you think or if you 
> have any questions.
> 
> 
> - josh
> 
> On Mon, Feb 8, 2010 at 11:41 AM, Blair Zajac <blair <at> orcaware.com 
> <mailto:blair <at> orcaware.com>> wrote:
> 
>     On Feb 8, 2010, at 8:29 AM, Paul Phillips wrote:
> 
>      > On Mon, Feb 08, 2010 at 08:06:41AM -0800, Blair Zajac wrote:
>      >> This looks like something that would do well in Scala's standard
>      >> library.
>      >
>      > I thought you were here the last few months.
> 
>     I've got 19,000 unread messages in my Scala mailbox and not enough
>     time to keep up on everything :(
> 
>     I found Josh's thread mentioning scalax.io <http://scalax.io>, but
>     the source repository at hg.scalaforge.org
>     <http://hg.scalaforge.org> is down.
> 
>     Is the most current discussion at
>     http://groups.google.com/group/scala-incubator/web/arm-questions ?
> 
>      >
>      >> BTW, the reason not to use structural subtyping is performance
>     and it
>      >> doesn't work with Oracle's java.sql.ResultSet subclass:
>      >
>      > http://lampsvn.epfl.ch/trac/scala/ticket/2318
>      > "Structural method is dispatched on non-public member when
>     overriding public member"
> 
>     Thanks.
> 
>     Blair
> 
> 

--

-- 
Blair Zajac, Ph.D.
CTO, OrcaWare Technologies
<blair <at> orcaware.com>
Subversion training, consulting and support
http://www.orcaware.com/svn/

Re: Adding ARM to Scala's standard library