# Collection functions?

**URL:** <https://discuss.kotlinlang.org/t/collection-functions/726>\
**Category:** Uncategorized\
**Created:** [October 17, 2013, 12:29am UTC](https://discuss.kotlinlang.org/t/collection-functions/726 "2013-10-17T00:29:16Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![HamsterofDeath](https://avatars.discourse-cdn.com/v4/letter/h/7feea3/32.png) [@HamsterofDeath](https://discuss.kotlinlang.org/u/HamsterofDeath)\
**Post date:** [October 17, 2013, 12:29am UTC](https://discuss.kotlinlang.org/t/collection-functions/726/1 "2013-10-17T00:29:16Z")

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i found some standard functions (select, map, fold), but not much more is this going to be improved? i am asking because i started to solve some euler problems ([http://projecteuler.net/](http://projecteuler.net/)) with kotlin (to take a look at kotlin), and i stumble upon everything that is missing compared to scala, haskell or clojure my first two missing features: strings are not treated as lists of characters, meaning there is no support for all the nice collection methods no "permutations" or "combinations" iterator

also i noticed that everything seems to be based on javas standard arraylist - didn’t you want to implement your own collections at some point?

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**Author:** ![abreslav](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.kotlinlang.org/abreslav/32/8279_2.png) [@abreslav](https://discuss.kotlinlang.org/u/abreslav)\
**Post date:** [October 17, 2013, 8:39am UTC](https://discuss.kotlinlang.org/t/collection-functions/726/2 "2013-10-17T08:39:04Z")

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Yes, this is going to be improved, and contributions are welcome.

About our own collections: we will implement them if there’s any real need, will reuse existing implementations where possible.

BTW, you may be interested to have a look here: [https://github.com/kotlin-projects/kotlin-euler](https://github.com/kotlin-projects/kotlin-euler)

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**Author:** ![HamsterofDeath](https://avatars.discourse-cdn.com/v4/letter/h/7feea3/32.png) [@HamsterofDeath](https://discuss.kotlinlang.org/u/HamsterofDeath)\
**Post date:** [October 17, 2013, 8:58am UTC](https://discuss.kotlinlang.org/t/collection-functions/726/3 "2013-10-17T08:58:35Z")

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nice^^

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**Author:** ![OliverPlow](https://avatars.discourse-cdn.com/v4/letter/o/d07c76/32.png) [@OliverPlow](https://discuss.kotlinlang.org/u/OliverPlow)\
**Post date:** [October 17, 2013, 10:39am UTC](https://discuss.kotlinlang.org/t/collection-functions/726/4 "2013-10-17T10:39:26Z")

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> strings are not treated as lists of characters, meaning there is no support for all the nice collection methods no "permutations" or "combinations" iterator

Strings not being treated as lists of characters got fixed in [KT-1859](http://youtrack.jetbrains.com/issue/KT-1859) The methods I suggested to be added back then to class String where all accepted (of course, they were inspired by the String iterators in Smalltalk ...): [https://github.com/JetBrains/kotlin/pull/158](https://github.com/JetBrains/kotlin/pull/158) So I guess people will be happy to deal with your pull request for permutations and combinations :-)