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#stdlib
- a
apatrida
12/29/2015, 4:18 AMI like the
as well, because I tend to turn into amapToSequence
early, then pop back out later.Sequence - a
apatrida
12/29/2015, 4:18 AMalthough popping out is easy withtoList() - j
jw
12/30/2015, 4:27 PMis there anything like
and/ordefaultIfEmpty
that I'm missing?switchIfEmpty - a
apatrida
12/30/2015, 9:01 PMdefine “empty”, do you mean empty for a string? (or another class) - a
apatrida
12/30/2015, 9:02 PMI use these:Copy code
combined with elvis operatorpublic fun String?.nullIfBlank(): String? = if (this.isNullOrBlank()) null else this public fun String?.nullIfEmpty(): String? = if (this.isNullOrEmpty()) null else this - a
apatrida
12/30/2015, 9:04 PMAll string extensions: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html#extension-functions Which has a reverse of this
which turns null into empty string.orEmpty() - j
jw
12/30/2015, 9:06 PMi'm talking about lists - j
jw
12/30/2015, 9:06 PMbut to answer your question, empty is well defined for a string - j
jw
12/30/2015, 9:06 PMCopy codeprivate fun <T> List<T>.defaultIfEmpty(value: T): List<T> { return if (isNotEmpty()) this else listOf(value) } - d
damian
12/30/2015, 9:07 PMand/or a lazy variant to match
?getOrElse()fun <T> List<T>.orIfEmpty(defaultValue: () -> List<T>) = if (isEmpty()) defaultValue() else this - j
jw
12/30/2015, 9:08 PMthat's
, for Rx at leastswitchIfEmpty - d
damian
12/30/2015, 9:08 PMahh, ok - j
jw
12/30/2015, 9:09 PMeasy to define, but seems applicable enough to warrant inclusion for the functional APIs - j
jw
12/30/2015, 9:09 PMi certainly use both quite a bit in Rx - d
damian
12/30/2015, 9:11 PMtrue, though a bit more of a pain to define if you want variants for all the collection/iterable/array/etc types like the other extensions have. all the more reason to include in the stdlib simple smile - j
jw
12/30/2015, 9:12 PMwill file a YouTrack with code then - a
apatrida
12/30/2015, 9:41 PM@jw: edited my note to be clearer, for what were you wanting to check empty. a string? (but now see your answer) - j
jw
12/30/2015, 9:50 PMyeah sorry I was in my own head, should have specified - k
kittinunf
12/31/2015, 7:50 AM+1 for including in stdlib, shouldn’t we generalize it into
. So anything that implementsSequence<T>
gets it too?Sequence - a
apatrida
01/02/2016, 4:10 AM@kittinunf: Sequence is not an ancestor or List nor does it have
semantics easily without asking for the iterator first and then checking hasNext() which is not the same as empty, but more like “done?"isEmpty() - j
jw
01/02/2016, 4:13 AMDisagree on all points - j
jw
01/02/2016, 4:13 AMIt's trivial to implement both as an iterable wrapper. A sequence is just an iterator provider anyway. - j
jw
01/02/2016, 4:14 AMAnd empty is well defined for iterator. - a
apatrida
01/02/2016, 4:24 AMok, so you can write a seperate one for sequence obviously, he was making a comment that there should be one generalized that works for both. - a
apatrida
01/02/2016, 4:26 AMiterator empty is
failing, but to me that isn’t empty, but done. which I guess in the case above you could call the same. but it is a separate implementation. finehasNext() - j
jw
01/02/2016, 4:28 AMdone is the same as empty - j
jw
01/02/2016, 4:28 AMif an iteration is done without producing any elements it is by definition empty - a
apatrida
01/02/2016, 4:30 AMAnd some sequences might be “iterate only once” so asking for the iterator just to ask hasNext() might cause it to be un-useful again. Trying to remember where in Kotlin there is, or was, such Sequences that were traverse once - a
apatrida
01/02/2016, 4:31 AMand regardless, my comment was more simply: you can’t “generalize” it to one method. - j
jw
01/02/2016, 4:31 AMthat's fine. if it returns true you use it