boundary (original) (raw)
scala.util.boundary
A boundary that can be exited by break calls. boundary and break represent a unified and superior alternative for the scala.util.control.NonLocalReturns and scala.util.control.Breaks APIs. The main differences are:
- Unified names:
boundaryto establish a scope,breakto leave it.breakcan optionally return a value. - Integration with exceptions.
breaks are logically non-fatal exceptions. TheBreakexception class extendsRuntimeExceptionand is optimized so that stack trace generation is suppressed. - Better performance: breaks to enclosing scopes in the same method can be rewritten to jumps.
Example usage:
import scala.util.boundary, boundary.break
def firstIndex[T](xs: List[T], elem: T): Int =
boundary:
for (x, i) <- xs.zipWithIndex do
if x == elem then break(i)
-1
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User code should call break.apply instead of throwing this exception directly.
User code should call break.apply instead of throwing this exception directly.
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Labels are targets indicating which boundary will be exited by a break.
Labels are targets indicating which boundary will be exited by a break.
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Run body with freshly generated label as implicit argument. Catch any breaks associated with that label and return their results instead of body's result.
Run body with freshly generated label as implicit argument. Catch any breaks associated with that label and return their results instead of body's result.
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Abort current computation and instead return value as the value of the enclosing boundary call that created label.
Abort current computation and instead return value as the value of the enclosing boundary call that created label.
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Abort current computation and instead continue after the boundary call that created label.
Abort current computation and instead continue after the boundary call that created label.
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