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On the empty string, .tail and .init now throw (instead of returning the empty string) #10851

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Merged
som-snytt merged 1 commit into from
Nov 25, 2024
Merged

On the empty string, .tail and .init now throw (instead of returning the empty string) #10851

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14 changes: 8 additions & 6 deletions src/library/scala/collection/StringOps.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1201,14 +1201,16 @@ final class StringOps(private val s: String) extends AnyVal {
def withFilter(p: Char => Boolean): StringOps.WithFilter = new StringOps.WithFilter(p, s)

/** The rest of the string without its first char.
* @note $unicodeunaware
*/
def tail: String = slice(1, s.length)
* @throws UnsupportedOperationException if the string is empty.
* @note $unicodeunaware
*/
def tail: String = if(s.isEmpty) throw new UnsupportedOperationException("tail of empty String") else slice(1, s.length)

/** The initial part of the string without its last char.
* @note $unicodeunaware
*/
def init: String = slice(0, s.length-1)
* @throws UnsupportedOperationException if the string is empty.
* @note $unicodeunaware
*/
def init: String = if(s.isEmpty) throw new UnsupportedOperationException("init of empty String") else slice(0, s.length-1)

/** A string containing the first `n` chars of this string.
* @note $unicodeunaware
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14 changes: 14 additions & 0 deletions test/junit/scala/collection/StringOpsTest.scala
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Expand Up @@ -102,4 +102,18 @@ class StringOpsTest {
assertEquals("de", "abcdef".collect { case c @ ('b' | 'c') => (c+2).toChar })
assertEquals(Seq('d'.toInt, 'e'.toInt), "abcdef".collect { case c @ ('b' | 'c') => (c+2).toInt })
}

@Test def init(): Unit = {
assertEquals("ab", "abc".init)
assertEquals("a", "ab".init)
assertEquals("", "a".init)
assertThrows[UnsupportedOperationException]("".init)
}

@Test def tail(): Unit = {
assertEquals("bc", "abc".tail)
assertEquals("b", "ab".tail)
assertEquals("", "a".tail)
assertThrows[UnsupportedOperationException]("".tail)
}
}