On the empty string, .tail and .init now throw (instead of returning the empty string)
#10851
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| * @throws NoSuchElementException if the string is empty. | ||
| * @note $unicodeunaware | ||
| */ | ||
| def tail: String = if(s.isEmpty) throw new NoSuchElementException("tail of empty String") else slice(1, s.length) |
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Most collections follow IterableOps in throwing UnsupportedOperation (but NSE for head and last).
A couple deviate and throw NSE. It's fine to leave it as it is here.
Example showing difficulty of enforcing uniformity of behavior:
scala> 0.until(0).tail
java.util.NoSuchElementException: tail on empty Range
at scala.collection.immutable.Range$.scala$collection$immutable$Range$$emptyRangeError(Range.scala:631)
at scala.collection.immutable.Range.tail(Range.scala:144)
... 30 elided
scala> 0.to(0).tail
val res4: scala.collection.immutable.Range = empty Range 0 until 0
example with descriptive message:
scala> collection.immutable.ArraySeq(Array(42)).tail.tail
java.lang.UnsupportedOperationException: tail of empty array
at scala.collection.ArrayOps$.tail$extension(ArrayOps.scala:346)
at scala.collection.immutable.ArraySeq.tail(ArraySeq.scala:242)
... 30 elided
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I meant to add, I'll merge as-is if you don't change it. Merges are paused until 2.13.15 is released, I assume.
| * @throws NoSuchElementException if the string is empty. | ||
| * @note $unicodeunaware | ||
| */ | ||
| def tail: String = if(s.isEmpty) throw new NoSuchElementException("tail of empty String") else slice(1, s.length) |
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I meant to add, I'll merge as-is if you don't change it. Merges are paused until 2.13.15 is released, I assume.
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Nice observation. Exception as shown is I always have a hiccup on String vs string, and favor String FSR. I would probably prefer naming a type, |
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It is rather bewildering trying to figure out what the "right" or "best" exception to throw is here, but I'll go along with the I have taken the liberty of squashing and force-pushing, so we can hit merge as soon as CI likes it. I will release-note this since it wouldn't surprise me if there is code out there inadvertently relying on the old behavior. |
.tail and .init now throw (instead of returning the empty string)
…y-string Throw exception on tail init when empty string
…y-string Throw exception on tail init when empty string
fix scala/bug#13026