control

package control

Visibility

Public
All

Type Members

class Breaks extends AnyRef

A class that can be instantiated for the break control abstraction.
A class that can be instantiated for the break control abstraction. Example usage:
```
val mybreaks = new Breaks
import mybreaks.{break, breakable}

breakable {
  for (...) {
    if (...) break()
  }
}
```
Calls to break from one instantiation of Breaks will never target breakable objects of some other instantiation.
trait ControlThrowable extends Throwable with NoStackTrace

A marker trait indicating that the Throwable it is mixed into is intended for flow control.
A marker trait indicating that the Throwable it is mixed into is intended for flow control.
Note that Throwable subclasses which extend this trait may extend any other Throwable subclass (eg. RuntimeException) and are not required to extend Throwable directly.
Instances of Throwable subclasses marked in this way should not normally be caught. Where catch-all behaviour is required ControlThrowable should be propagated, for example:
```
import scala.util.control.ControlThrowable

try {
  // Body might throw arbitrarily
} catch {
  case c: ControlThrowable => throw c // propagate
  case t: Exception        => log(t)  // log and suppress
}
```
trait NoStackTrace extends Throwable

A trait for exceptions which, for efficiency reasons, do not fill in the stack trace.
A trait for exceptions which, for efficiency reasons, do not fill in the stack trace. Stack trace suppression can be disabled on a global basis via a system property wrapper in scala.sys.SystemProperties.

Since
2.8

Value Members

object Breaks extends Breaks

An object that can be used for the break control abstraction.
An object that can be used for the break control abstraction. Example usage:
```
import Breaks.{break, breakable}

breakable {
  for (...) {
    if (...) break
  }
}
```
object Exception

Classes representing the components of exception handling.
Classes representing the components of exception handling. Each class is independently composable. Some example usages:
```
import scala.util.control.Exception._
import java.net._

val s = "http://www.scala-lang.org/"
val x1 = catching(classOf[MalformedURLException]) opt new URL(s)
val x2 = catching(classOf[MalformedURLException], classOf[NullPointerException]) either new URL(s)
```
This class differs from scala.util.Try in that it focuses on composing exception handlers rather than composing behavior. All behavior should be composed first and fed to a Catch object using one of the opt or either methods.
object NoStackTrace extends Serializable
object NonFatal

Extractor of non-fatal Throwables.
Extractor of non-fatal Throwables. Will not match fatal errors like VirtualMachineError (for example, OutOfMemoryError and StackOverflowError, subclasses of VirtualMachineError), ThreadDeath, LinkageError, InterruptedException, ControlThrowable.
Note that scala.util.control.ControlThrowable, an internal Throwable, is not matched by NonFatal (and would therefore be thrown).
For example, all harmless Throwables can be caught by:
```
try {
  // dangerous stuff
} catch {
  case NonFatal(e) => log.error(e, "Something not that bad.")
 // or
  case e if NonFatal(e) => log.error(e, "Something not that bad.")
}
```
object TailCalls

Methods exported by this object implement tail calls via trampolining.
Methods exported by this object implement tail calls via trampolining. Tail calling methods have to return their result using done or call the next method using tailcall. Both return a TailRec object. The result of evaluating a tailcalling function can be retrieved from a Tailrec value using method result. Implemented as described in "Stackless Scala with Free Monads" http://blog.higher-order.com/assets/trampolines.pdf
Here's a usage example:
```
import scala.util.control.TailCalls._

def isEven(xs: List[Int]): TailRec[Boolean] =
  if (xs.isEmpty) done(true) else tailcall(isOdd(xs.tail))

def isOdd(xs: List[Int]): TailRec[Boolean] =
 if (xs.isEmpty) done(false) else tailcall(isEven(xs.tail))

isEven((1 to 100000).toList).result

def fib(n: Int): TailRec[Int] =
  if (n < 2) done(n) else for {
    x <- tailcall(fib(n - 1))
    y <- tailcall(fib(n - 2))
  } yield (x + y)

fib(40).result
```

Ungrouped