Created
July 16, 2012 02:42
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trouble with jgit & scala.collection.JavaConversions
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| // import scala.collection.JavaConversions._ | |
| scala> val git = new Git(new FileRepositoryBuilder().findGitDir(new java.io.File("/path/to/repos")).readEnvironment().build()) | |
| git: org.eclipse.jgit.api.Git = org.eclipse.jgit.api.Git@18ed36fb | |
| scala> git.log.addPath("foo").call.head | |
| res49: org.eclipse.jgit.revwalk.RevCommit = commit c4554d9f46de49e449242a2aa75d39874dc99498 1342332998 ----sp | |
| scala> git.log.addPath("foo").call.headOption | |
| res50: Option[org.eclipse.jgit.revwalk.RevCommit] = Some(commit d3107ef998b25d70f86f1a5d530c31c02507d59e 1342012813 ----sp) | |
| scala> git.log.addPath("foo").call.toList.head | |
| res51: org.eclipse.jgit.revwalk.RevCommit = commit c4554d9f46de49e449242a2aa75d39874dc99498 1342332998 ----sp | |
| scala> git.log.addPath("foo").call.toList.headOption | |
| res52: Option[org.eclipse.jgit.revwalk.RevCommit] = Some(commit c4554d9f46de49e449242a2aa75d39874dc99498 1342332998 ----sp) | |
| scala> git.log.addPath("foo").call.toList | |
| res53: List[org.eclipse.jgit.revwalk.RevCommit] = List(commit c4554d9f46de49e449242a2aa75d39874dc99498 1342332998 ----sp, commit d3107ef998b25d70f86f1a5d530c31c02507d59e 1342012813 ----sp) | |
| // headOption fetches second element?? |
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https://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/JavaConversions.scala#L401
https://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/JavaConversions.scala#L587
JIterableWrapperがつくられるhttps://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/TraversableLike.scala#L422
isEmptyが呼ばれるhttps://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/IterableLike.scala#L81-82
https://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/IterableLike.scala#L63
isEmptyのために新しいiteratorがつくられる(そのiteratorが先頭の要素保持しちゃう)https://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/TraversableLike.scala#L402-416
head呼ぶhttps://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/IterableLike.scala#L72
headの中で呼ばれるforeachも新しいIterator生成するが、isEmptyのときに生成した Iterator が先頭の要素を保持というか消費してて、二回目にここで生成したiteratorは、2番目の要素が先頭になってる