anything like LINQ?

[Raoul Duke]

(i'm searching but haven't found a concise answer of yes yet :-)

Quaere comes close
http://www.theserverside.com/news/thread.tss?thread_id=46887
but doesn't have closures etc?

would this can this should this work better in with Scala? or is there
another similar alternative?

thanks.

[Arrgh]

For projection at least Scala is in reasonable shape already;  
declarative insertion, deletion and updates are a different matter  
that might want some thought.

LINQ:

     string [] cities = { ?Auckland?, ?Oslo?, ?Sydney?,
            ?Seattle?, ?Paris?, ?Los Angeles? };

     IEnumerable places = from city in cities
            where city.Length > 5
                  orderby city descending
            select city;

scala> val cities = List("Auckland", "Oslo", "Sydney", "Seattle",  
"Paris", "Los Angeles")

scala> val places = scala.util.Sorting.stableSort(for (c <- cities if  
c.length > 5) yield c)
places: List[java.lang.String] = List(Auckland, Los Angeles, Seattle, Sydney)

It would be... interesting... to think about adding sorting to for  
comprehensions. :)

[Henry Ware-2]

Hi Raoul,

The things on the Quaere page are easy in Scala with sequence comprehensions:

val num= List(5, 4, 1, 3, 9, 8, 6, 7, 2, 0);

val low=for (i <- num if i < 5 ) yield i;
//or
val low2= num.filter(_ < 5);

def productNames(products: Seq[{def getProductName:String}])=for (p <- products ) yield p.getProductName;

val words=List("aPPLE", "BlUeBeRrY", "cHeRry");

val upDown=for (w <- words) yield new { val lower=w.toLowerCase ; val upper=w.toUpperCase };

println(upDown.head.lower);

//Seq doesn't have as sort because Seq's might be infinite. 
upDown.toList.sort (_.upper.length<_.lower.length).map(_.lower)

// joins are easy too:
val uppersWithLength= for (w<-upDown; i<- num if w.lower.length>i) yield (i,w.upper);

SFAIK, there is no automatic translations of sequence comprehensions to jdbc/sql calls.

-Henry

On Jan 4, 2008 9:01 PM, Raoul Duke <raould@...> wrote:

(i'm searching but haven't found a concise answer of yes yet :-)

Quaere comes close
http://www.theserverside.com/news/thread.tss?thread_id=46887
but doesn't have closures etc?

would this can this should this work better in with Scala? or is there
another similar alternative?

thanks.

[Jorge Ortiz-3]

SFAIK, there is no automatic translations of sequence comprehensions to jdbc/sql calls.

 
My understanding is that this would require support for expression trees, which C# 3.0 has and Scala does not.

--j

[David MacIver]

On Jan 5, 2008 11:31 PM, Jorge Eugenio Ortiz Hinojosa
<jorge.ortiz@...> wrote:
>
>
> > SFAIK, there is no automatic translations of sequence comprehensions to
> jdbc/sql calls.
>
> My understanding is that this would require support for expression trees,
> which C# 3.0 has and Scala does not.

Actually, it does. It's just utterly undocumented and kinda clunky. I
think it's something which got half finished and then sidelined until
decisions about reflection, metaprogramming, etc. were finalised.

scala> import scala.reflect._;
import scala.reflect._

scala> val addition : Code[(Int, Int) => Int] = _+_
addition: scala.reflect.Code[(Int, Int) => Int] = scala.reflect.Code@1a15597

scala> Print(addition);
res0: String = (x$1, x$2) => x$1.$plus(x$2)

scala> println(addition.tree);
Function(List(LocalValue(NoSymbol,x$1,PrefixedType(ThisType(Class(scala)),Class(scala.Int))),
LocalValue(NoSymbol,x$2,PrefixedType(ThisType(Class(scala)),Class(scala.Int)))),Apply(Select(Ident(LocalValue(NoSymbol,x$1,PrefixedType(ThisType(Class(scala)),Class(scala.Int)))),Method(scala.Int.$plus,MethodType(List(PrefixedType(ThisType(Class(scala)),Class(scala.Int))),PrefixedType(ThisType(Class(scala)),Class(scala.Int))))),List(Ident(LocalValue(NoSymbol,x$2,PrefixedType(ThisType(Class(scala)),Class(scala.Int)))))))

I don't think I'd recommend using this in its present state. :-)
Anyone more knowledgeable than me want to comment on it?

[Jorge Ortiz-3]

Hot!

I'd love to see Expression Trees officially making it into Scala.

On 1/5/08, David MacIver <david.maciver@...> wrote:

On Jan 5, 2008 11:31 PM, Jorge Eugenio Ortiz Hinojosa
<jorge.ortiz@...> wrote:
>
>
> > SFAIK, there is no automatic translations of sequence comprehensions to
> jdbc/sql calls.
>
> My understanding is that this would require support for expression trees,
> which C# 3.0 has and Scala does not.

Actually, it does. It's just utterly undocumented and kinda clunky. I
think it's something which got half finished and then sidelined until
decisions about reflection, metaprogramming, etc. were finalised.

scala> import scala.reflect._;
import scala.reflect._

scala> val addition : Code[(Int, Int) => Int] = _+_
addition: scala.reflect.Code[(Int, Int) => Int] = scala.reflect.Code@1a15597

scala> Print(addition);
res0: String = (x$1, x$2) => x$1.$plus(x$2)

scala> println(addition.tree);
Function(List(LocalValue(NoSymbol,x$1,PrefixedType(ThisType(Class(scala)),Class(scala.Int))),
LocalValue(NoSymbol,x$2,PrefixedType(ThisType(Class(scala)),Class( scala.Int)))),Apply(Select(Ident(LocalValue(NoSymbol,x$1,PrefixedType(ThisType(Class(scala)),Class(scala.Int)))),Method(scala.Int.$plus,MethodType(List(PrefixedType(ThisType(Class(scala)),Class(scala.Int))),PrefixedType(ThisType(Class(scala)),Class( scala.Int))))),List(Ident(LocalValue(NoSymbol,x$2,PrefixedType(ThisType(Class(scala)),Class(scala.Int)))))))

I don't think I'd recommend using this in its present state. :-)
Anyone more knowledgeable than me want to comment on it?

[Martin Odersky]

On Jan 6, 2008 1:54 AM, Jorge Eugenio Ortiz Hinojosa
<jorge.ortiz@...> wrote:
> Hot!
>
> I'd love to see Expression Trees officially making it into Scala.
>
There's actually a move to do this, but the current approach was
completely experimental and turned out to be a dead end. That's why it
never got documented. But the new annotations can already refer to
AST's, and we plan to generalize this.

Cheers

 -- Martin