IO

Hi Ken,

Ken Faulkner wrote:
> Will we ever get to the state (as in Python) where something like:
>
> import scala.io.binaryfiles
>
> var fd = binaryfiles.open("foo.img", "w")
> fd.write( myBinaryData )
> fd.close()
>
>
> or
>
> var fd = binaryfiles.open("foo.img")
> var data = fd.read()
> fd.close()
>
Firstly, that's screaming for a closure! If such a more scalaish
library was written I'd assume the use would look something like:

var data =
BinaryFiles.using("foo.img") { fd =>
fd.read()
}

or even:

var data =
for (fd <- BinaryFiles.using("foo.img")) {
fd.read()
}

The library code for "using" would make sure the file got closed even if
an exception was thrown during the execution of the block, similar to
RAII in C++.

Some stuff to this end is in scalax (http://scalax.scalaforge.org/).
Not sure about binary files, but for example this allows you to write
something much more scalaish to read lines from a text file:

val lines : List[String] = testFile.lines.toList

or indeed:

val words =
for (line <- testFile.lines.toList; word <-
line.split("\\s+").toList) yield {
word
}

I don't believe anything like this is in the scala standard library, but
it's been a while since I used it for file IO.

Thanks,

Matt

2009/4/5 Ken Faulkner :
> Hi
> Does anyone know if its planned that Scala will always simply depend on the
> various Java IO libs that exist out there, or if something "Scala-ish" will
> eventually be incorporated into the language/standard library?

I don't think there are formal plans for a decently complete scala.io,
but it's definitely be discussed. I'm pretty certain that there will
be one at some point, but I don't know when.

Yes, yes! Lack of handy IO utilities — is a big drawback of the
standard scala library (compared to python's one for example).

There are classes in the scalax library:

http://scalax.scalaforge.org/api/

That allow something like this:

InputStreamResource.url("http://server/file.txt")
.reader("ch1251").lines.map(_.toInt).foreach { ... }

or

for (r <- ReaderResource.file("/etc/passwd")) {
// r is a Reader
}

Hope, these or similar implementations will be added to the scala
standard library one day. IO utilities are really needed for everyday
programming.

S.

On Sun, Apr 5, 2009 at 15:32, Ken Faulkner wrote:
> Hi
> Does anyone know if its planned that Scala will always simply depend on the
> various Java IO libs that exist out there, or if something "Scala-ish" will
> eventually be incorporated into the language/standard library?
> I'm only in the process of learning it, and I have to admit up front to NOT
> being a Java fan. Scala the language I think definitely looks like something
> I want to use more and more but having all these "please go and use standard
> Java lib" is a bit jarring. For example, something as simple as
> reading/writing some binary file screams (to me at least) as something ugly
> and non-Scala looking when FileOutputStreams combined with
> ObjectOutputStreams from Java.io are imported and used about the place.
> Considering I'm fairly hostile to Java maybe I'm in a minority (my
> background is C/C++, Java and more recently Python).
> Will we ever get to the state (as in Python) where something like:
> import scala.io.binaryfiles
> var fd = binaryfiles.open("foo.img", "w")
> fd.write( myBinaryData )
> fd.close()
>
> or
> var fd = binaryfiles.open("foo.img")
> var data = fd.read()
> fd.close()
>
> Or am I just not advanced enough in my Scala learning yet?
> Ken
>
>
>

Hi
Does anyone know if its planned that Scala will always simply depend on the various Java IO libs that exist out there, or if something "Scala-ish" will eventually be incorporated into the language/standard library?
I'm only in the process of learning it, and I have to admit up front to NOT being a Java fan. Scala the language I think definitely looks like something I want to use more and more but having all these "please go and use standard Java lib" is a bit jarring. For example, something as simple as reading/writing some binary file screams (to me at least) as something ugly and non-Scala looking when FileOutputStreams combined with ObjectOutputStreams from Java.io are imported and used about the place. Considering I'm fairly hostile to Java maybe I'm in a minority (my background is C/C++, Java and more recently Python).
Will we ever get to the state (as in Python) where something like:
import scala.io.binaryfiles
var fd = binaryfiles.open("foo.img", "w") fd.write( myBinaryData )fd.close()

or
var fd = binaryfiles.open("foo.img")var data = fd.read()fd.close()

Or am I just not advanced enough in my Scala learning yet?
Ken

On Sunday April 5 2009, Ricky Clarkson wrote:
> Until something is standardised on, you can easily write something
> yourself that wraps the Java libs. Probably most of us have a small
> set of IO utilities. How does Python manage to ensure the file is
> closed if writing fails somehow?

Now you've done it.

(This came up a couple of weeks ago, if you'll recall. As I recall it
described, they have shut-down hooks that iterate over all the open
file handles and flush and close them.)

Randall Schulz

On Sunday April 5 2009, Ricky Clarkson wrote:
> Until something is standardised on, you can easily write something
> yourself that wraps the Java libs.  Probably most of us have a small
> set of IO utilities.  How does Python manage to ensure the file is
> closed if writing fails somehow?

Now you've done it.

(This came up a couple of weeks ago, if you'll recall. As I recall it
described, they have shut-down hooks that iterate over all the open
file handles and flush and close them.)


Randall Schulz

On Sunday April 5 2009, Ricky Clarkson wrote:
> So how does that work for a long-running application rather than one
> that terminates before all resources are consumed?

I don't know. Perhaps Mr. Russ Paielli will inform us.

RRS

Yes, yes! Lack of handy IO utilities — is a big drawback of the
standard scala library (compared to python's one for example).

There are classes in the scalax library:

http://scalax.scalaforge.org/api/

That allow something like this:

InputStreamResource.url("http://server/file.txt")
 .reader("ch1251").lines.map(_.toInt).foreach { ... }

or

for (r <- ReaderResource.file("/etc/passwd")) {
 // r is a Reader
}

Hope, these or similar implementations will be added to the scala
standard library one day. IO utilities are really needed for everyday
programming.


S.

On Sun, Apr 5, 2009 at 15:32, Ken Faulkner <ken.faulkner@gmail.com> wrote:
> Hi
> Does anyone know if its planned that Scala will always simply depend on the
> various Java IO libs that exist out there, or if something "Scala-ish" will
> eventually be incorporated into the language/standard library?
> I'm only in the process of learning it, and I have to admit up front to NOT
> being a Java fan. Scala the language I think definitely looks like something
> I want to use more and more but having all these "please go and use standard
> Java lib" is a bit jarring. For example, something as simple as
> reading/writing some binary file screams (to me at least) as something ugly
> and non-Scala looking when FileOutputStreams combined with
> ObjectOutputStreams from Java.io are imported and used about the place.
> Considering I'm fairly hostile to Java maybe I'm in a minority (my
> background is C/C++, Java and more recently Python).
> Will we ever get to the state (as in Python) where something like:
> import scala.io.binaryfiles
> var fd = binaryfiles.open("foo.img", "w")
> fd.write( myBinaryData )
> fd.close()
>
> or
> var fd = binaryfiles.open("foo.img")
> var data = fd.read()
> fd.close()
>
> Or am I just not advanced enough in my Scala learning yet?
> Ken
>
>
>

Until something is standardised on, you can easily write something yourself that wraps the Java libs.  Probably most of us have a small set of IO utilities.  How does Python manage to ensure the file is closed if writing fails somehow?

2009/4/5 Ken Faulkner <ken.faulkner@gmail.com>

Hi
Does anyone know if its planned that Scala will always simply depend on the various Java IO libs that exist out there, or if something "Scala-ish" will eventually be incorporated into the language/standard library?
I'm only in the process of learning it, and I have to admit up front to NOT being a Java fan. Scala the language I think definitely looks like something I want to use more and more but having all these "please go and use standard Java lib" is a bit jarring. For example, something as simple as reading/writing some binary file screams (to me at least) as something ugly and non-Scala looking when FileOutputStreams combined with ObjectOutputStreams from Java.io are imported and used about the place. Considering I'm fairly hostile to Java maybe I'm in a minority (my background is C/C++, Java and more recently Python).
Will we ever get to the state (as in Python) where something like:
import scala.io.binaryfiles
var fd = binaryfiles.open("foo.img", "w") fd.write( myBinaryData )fd.close()

or
var fd = binaryfiles.open("foo.img")var data = fd.read()fd.close()

Or am I just not advanced enough in my Scala learning yet?
Ken