File System Traversal

On Tue, Feb 7, 2012 at 22:39, Eric Kolotyluk wrote:
> I got some nice code a while ago from Joshua Suereth which included
>
>    // We create a 'collection' that can iterate over files.
>    object files extends Traversable[File] {
>       override def foreach[U](f: File => U): Unit = {
>          // Note we could remove recursion here with some work.  You should
> make this recurse in whatever order you
>          // desire for optimum early-exit in your algorithm.
>          def iter(file: File) : Unit =
>            if(file.isDirectory) file.listFiles foreach iter
>            else f(file)
>          iter(new File(sourceName))
>       }
>    }
>
> I was just wondering if there is already something in the Scala libraries
> that does this as it seems like a really common thing to do - traverse a set
> of files and directories.
>
> Scala often seems to have nice little utilities for basic things like this,
> but I am not always sure of the best way to find them. For example, it would
> be nice to just do something like
>
>   val scalaFiles = File("src").traversable.view.filter(_.getName endsWith
> ".scala")
>
> But Scala does not seem to have its own file system API, nor can I find
> anything suitable in Scalaz.
>
> I guess there is the basic question of trade-offs: how much stuff should
> people just know how to do in Scala because it is easy to express (like
> Josh's code) and how much should be found in the libraries because it is a
> common and simple operation.

I haven't looked at it in a long while, but check
http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/overview.

In particular, on Files API, there's stuff like this:

http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/file/descendant_processing
http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/file/descendants_using_path_sets

Note that traversable are single dimension structures, while file
systems are trees at best, and disjunctive cyclical graphs at worst.

On Wed, Feb 8, 2012 at 00:02, Daniel Sobral wrote:
> On Tue, Feb 7, 2012 at 22:39, Eric Kolotyluk wrote:
>> I got some nice code a while ago from Joshua Suereth which included
>>
>>    // We create a 'collection' that can iterate over files.
>>    object files extends Traversable[File] {
>>       override def foreach[U](f: File => U): Unit = {
>>          // Note we could remove recursion here with some work.  You should
>> make this recurse in whatever order you
>>          // desire for optimum early-exit in your algorithm.
>>          def iter(file: File) : Unit =
>>            if(file.isDirectory) file.listFiles foreach iter
>>            else f(file)
>>          iter(new File(sourceName))
>>       }
>>    }
>>
>> I was just wondering if there is already something in the Scala libraries
>> that does this as it seems like a really common thing to do - traverse a set
>> of files and directories.
>>
>> Scala often seems to have nice little utilities for basic things like this,
>> but I am not always sure of the best way to find them. For example, it would
>> be nice to just do something like
>>
>>   val scalaFiles = File("src").traversable.view.filter(_.getName endsWith
>> ".scala")
>>
>> But Scala does not seem to have its own file system API, nor can I find
>> anything suitable in Scalaz.
>>
>> I guess there is the basic question of trade-offs: how much stuff should
>> people just know how to do in Scala because it is easy to express (like
>> Josh's code) and how much should be found in the libraries because it is a
>> common and simple operation.
>
> I haven't looked at it in a long while, but check
> http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/overview.
>
>
> --
> Daniel C. Sobral
>
> I travel to the future all the time.

On 2012-02-07 6:06 PM, Daniel Sobral wrote:
> In particular, on Files API, there's stuff like this:
>
> http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/file/descendant_processing
> http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/file/descendants_using_path_sets
>
> Note that traversable are single dimension structures, while file
> systems are trees at best, and disjunctive cyclical graphs at worst.

In this case what I really want is a single dimension structure because
I am just filtering files, and I don't really care about any other
structure. However, I really don't want to get in a loop or visit the
same file twice, so thanks for pointing that out.

>
> On Wed, Feb 8, 2012 at 00:02, Daniel Sobral wrote:
>> On Tue, Feb 7, 2012 at 22:39, Eric Kolotyluk wrote:
>>> I got some nice code a while ago from Joshua Suereth which included
>>>
>>> // We create a 'collection' that can iterate over files.
>>> object files extends Traversable[File] {
>>> override def foreach[U](f: File => U): Unit = {
>>> // Note we could remove recursion here with some work. You should
>>> make this recurse in whatever order you
>>> // desire for optimum early-exit in your algorithm.
>>> def iter(file: File) : Unit =
>>> if(file.isDirectory) file.listFiles foreach iter
>>> else f(file)
>>> iter(new File(sourceName))
>>> }
>>> }
>>>
>>> I was just wondering if there is already something in the Scala libraries
>>> that does this as it seems like a really common thing to do - traverse a set
>>> of files and directories.
>>>
>>> Scala often seems to have nice little utilities for basic things like this,
>>> but I am not always sure of the best way to find them. For example, it would
>>> be nice to just do something like
>>>
>>> val scalaFiles = File("src").traversable.view.filter(_.getName endsWith
>>> ".scala")
>>>
>>> But Scala does not seem to have its own file system API, nor can I find
>>> anything suitable in Scalaz.
>>>
>>> I guess there is the basic question of trade-offs: how much stuff should
>>> people just know how to do in Scala because it is easy to express (like
>>> Josh's code) and how much should be found in the libraries because it is a
>>> common and simple operation.
>> I haven't looked at it in a long while, but check
>> http://jesseeichar.github.com/scala-io-doc/0.3.0/index.html#!/overview.
>>
>>
>> --
>> Daniel C. Sobral
>>
>> I travel to the future all the time.
>
>