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How to convert List[List[Map[String,String]]] to List[Map[String,String]]. Example: List("I", "can't", List("do", "this")), Expecting result: List("I", "can't", "do", "this"). Here is what you can do to flag awwsmm: awwsmm consistently posts content that violates DEV Community's Once suspended, awwsmm will not be able to comment or publish posts until their suspension is removed. GenTraversableOnce [B] is a predicate or condition to be applied on each element of the collection. What does "Welcome to SeaWorld, kid!" Is electrical panel safe after arc flash? Dive in for free with a 10-day trial of the OReilly learning platformthen explore all the other resources our members count on to build skills and solve problems every day. Partial functions as case sequences are really handy, and so are the map() and flatMap() methods. Instead of blindly using flatten, we can instead think about the structure of our data. It will become hidden in your post, but will still be visible via the comment's permalink. I share those examples in this tutorial. This is Recipe 10.15, "How to Flatten a List of Lists in Scala with flatten " You have a list of lists (a sequence of sequences) and want to create one list (sequence) from them. For real code, of course, there, That wouldn't work in this case. P07 (**) Flatten a nested list structure. I assume that you are asking for using flatmap method. Thanks for keeping DEV Community safe. Its tail recursive version is rather simple, This initially seemed to be a good solution. The issue with this approach is that. Because of the way flatMap works, it flattens the resulting list of strings into a sequence of characters ( Seq [Char] ). The specific situation is this: You're using map (or a for/yield expression) to create a new collection from an existing collection. We're a place where coders share, stay up-to-date and grow their careers. I don't know why it don't work, it returns List(1, 1, 2, List(3, List(5, 8))) but it should be List(1, 1, 2, 3, 5, 8). Are you sure you want to hide this comment? They then step through the elements in the list and apply the provided function to them. This function works as expected, but there is no check of the incoming data types. If that gives you what you need, call flatMap instead of map and flatten. This is an excerpt from the Scala Cookbook (partially modified for the internet). Scala flatten list of String and List[String], Scala flatten a map with list as key and string as value, SciFi novel about a portal/hole/doorway (possibly in the desert) from which random objects appear. If it is the first time that Unflagging awwsmm will restore default visibility to their posts. rev2023.6.5.43476. (List.scala:428) at scala.collection.immutable.Nil$.head(List.scala:425) . How to merge a map of String to List functionally? The GitHub issues page is the best place to submit corrections. As for the implementation of subWords well, its a work in progress: By Alvin Alexander. rev2023.6.5.43476. Instead do the matching in place like so: My, equivalent to SDJMcHattie's, solution. How to flatten a tuple of lists to a list of lists in Scala, flattening list of lists in Scala with out using flatten method giving bad result, Converting a List into a Nested List in Scala, How to flatten a list of lists when the root type is List[Any], Scala - merge Lists into one List element-wise, Nouns which are masculine when singular and feminine when plural, How to check if a string ended with an Escape Sequence (\n). Try to use a Tree or something else. functional programming, Share on: Twitter Could you tell me what this message means and what to do to let my Ubuntu boots? Pattern matching! To demonstrate this, first create a list of lists: scala> val lol = List (List (1,2), List (3,4)) lol: List [List [Int]] = List (List (1, 2), List (3, 4)) Calling the flatten method on this list of lists creates one new list: Write a Scala program to triplicate each element immediately next to the given list of integers. @maasg it's an answer, all right. How to check if a string ended with an Escape Sequence (\n), Questions about a tcolorbox without a frame. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. The key point in flattening is the possibility to tell apart a list from a non-list element, to rule the call of another recursion. For further actions, you may consider blocking this person and/or reporting abuse. Scala allows to define partial functions as case sequences (see here) so the solution is pretty simple. Solution Use flatMap in situations where you run map followed by flatten. map and join functions of the Option and List Monads. Scala If you look at that page, youll see that the other examples use map, but this particular example uses flatMap. In the first example, this is easy. (Imagine trying to write that code with only a for loop.). Follow us on Facebook To subscribe to this RSS feed, copy and paste this URL into your RSS reader. List methods Once you have a populated list, the following examples show some of the methods you can call on it. Though I use the term list here, the flatten method isnt limited to a List; it works with other sequences (Array, ArrayBuffer, Vector, etc.) In our raggedList example, we simply don't have a way to convert the type Any to the GenTraversableOnce type required by flatten. Instead do the matching in place like so: def flatten (xs: List [Any]): List [Any] = xs match { case Nil => Nil case (head: List [_]) :: tail => flatten (head) ++ flatten (tail) case head :: tail => head :: flatten (tail) } Share. Its an interesting exercise to look at those examples and wonder why this is. After a while your brain will naturally think "flat map" without needing those intermediate steps. Why not use it? Well this page talks a lot about typed patterns and type erasure in Scala. The following warning was printed by the compiler "warning: there were 2 unchecked warnings; re-run with -unchecked for details" and running it with the suggested options results in "warning: non variable type-argument A in type pattern List[A] is unchecked since it is eliminated by erasure". This means that when we try to flatten the List, we're trying to apply a method with the signature: This signature might be a little intimidating, but the important bit is that -- in the case of nestedList, we're trying to convert an Any to another Scala object with a generic type B, returning a List of that type, List[B]. I have a list of String and List[String]. Does the policy change for AI-generated content affect users who (want to) how to get this result list result = List(1,2,3,4,5,6,7) from val l1 = List(1,2,List(3,List(4,5,6),5,6,7) in scala? While map() builds the resulting collection concatenating the results of each application, flatMap() concatenates the elements of the collection that results from each application. Exactly my thoughts. and Twitter for latest update. flatten: Transforms a list of lists into a single list: flatMap(f) When working with sequences, it works like map followed by flatten: map(f) Return a new sequence by applying the function f to each element in the List: . What should be the criteria of convergence over ENCUT? This is not really a good approach, because you subvert the type safety this way, and end up with a List[AnyRef], that can contain well, anything. The flatten method will collapse the elements of a collection to create a single collection with elements of the same type. Colour composition of Bromine during diffusion? Not the answer you're looking for? If you want to add in some data during the map this is what you want. Once unpublished, this post will become invisible to the public and only accessible to Andrew (he/him). Hope that it makes sense for you, @akki, why don't you try it yourself? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, the above list is heterogeneous, flatten wont work there. But the sum method needs a List[Int]; how do you get there from here? As shown in the previous recipe, flatten works very well with a list of Some and None elements. My first solution was this. I have a list: List [List [A]] which I want to convert into List [A] How can that be achieved recursively? How can we do that? While its good to see how flatMap works on sequences, it really shines when it comes to working with the Scala Option/Some/None classes (and similar classes like Try and Either). Most upvoted and relevant comments will be first. Could algae and biomimicry create a carbon neutral jetpack? :), Scala flatten list of String and List[String], scala-lang.org/api/current/#scala.collection.immutable.List, Building a safer community: Announcing our new Code of Conduct, Balancing a PhD program with a startup career (Ep. Email Also, here's a repeat of those earlier links: By Alvin Alexander. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Part III: The Deep End, What's Wrong This Time? List objects provide a very interesting method, flatMap() that, just like map(), applies a given function to all elements of the list. Flattening of List is converting a list of multiple List into a single List. Using Ints again we get what might be a more understandable result: this is a List[Any], where Any is the only class which can represent both Int as well as List[Int] values. Where does the transaction fee go after balance transfer without a treasury pallet in solo chain? What should be the criteria of convergence over ENCUT? Calling flatten on a List[List[String]] does the job: If you really want to have fun, capitalize each element in the Transform a list List[String, String] into List[String, List[String]] in Scala? as well: In the real world, you might use flatten to convert a list of couples attending What if the first element is not a List, but the rest of the elements are? If someone does not understand this line of the accepted solution, or did not know that you can annotate a pattern with a type: Then look at an equivalent without the type annotation: So, just for better understanding some alternatives: By the way, the second posted answer will do the following, which you probably don't want. OReilly members experience books, live events, courses curated by job role, and more from OReilly and nearly 200 top publishers. Call flatten: Success! One problem, though: map gave you a list of lists. Here, map() is used to produce a list for each element containing the element itself and the element multiplied by two. To learn more, see our tips on writing great answers. Connect and share knowledge within a single location that is structured and easy to search. You may write to us at reach[at]yahoo[dot]com or visit us Pay attention to the fact that this function has to drop the type check just like the first one. Not the answer you're looking for? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This is a fun as an exercise. The next example shows how to use flatMap with an Option. @MuhammadHewedy There are no commas, so it's not a tuple - it's just parentheses to force the correct associativity (without them, Building a safer community: Announcing our new Code of Conduct, Balancing a PhD program with a startup career (Ep. Is it possible? In Scala, it's easy to flatten a nested List of List s with the flatten method: scala> val nestedList = List(List(1), List(2), List(3, 4)) nestedList: List[List[Int]] = List(List(1), List(2), List(3, 4)) scala> nestedList.flatten res28: List[Int] = List(1, 2, 3, 4) .but what if your List has more than one, or uneven levels of nesting? Why is this screw on the wing of DASH-8 Q400 sticking out, is it safe? 576), We are graduating the updated button styling for vote arrows. You have a list of all the sub-words from the original list of words. Thanks for contributing an answer to Stack Overflow! (Other than the fact that the older answer is cleaner and more concise. flatMap(), conversely, returns the concatenation of all elements. 99 Scala Problems 01 - Find the last element of a list, 99 Scala Problems 02 - Find the last but one element of a list, 99 Scala Problems 03 - Find the Kth element of a list, 99 Scala Problems 04 - Find the number of elements of a list, 99 Scala Problems 06 - Find out whether a list is a palindrome, 99 Scala Problems 08 - Eliminate consecutive duplicates of list elements, 99 Scala Problems 09 - Pack consecutive duplicates of list elements into sublists. 576), We are graduating the updated button styling for vote arrows. Do the mountains formed by a divergent boundary form on either coast of the resulting channel, or on the part that has not yet separated? How to flatten array to its tuple elements -scala. That is, it transforms the single Int to the three resulting Ints: This great example comes from the following URL: See that page for more map and flatMap examples. Which comes first: Continuous Integration/Continuous Delivery (CI/CD) or microservices? Thanks for contributing an answer to Stack Overflow! Colour composition of Bromine during diffusion? The question was whether the was a better way to flatten than the OP had. flatten example in docs will be helpful: scala-lang.org/api/current/#scala.collection.immutable.List When I was first trying to learn Scala, and cram the collections'flatMap method into my brain, I scoured books and the internet for great flatMap examples. How to Flatten Collections in Scala Last modified: December 2, 2022 Written by: baeldung Scala Collections List 1. Use the flatten method to convert a list of lists into a single list. Next: Write a Scala program to triplicate each element immediately next to the given list of integers. We are closing our Disqus commenting system for some maintenanace issues. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. LinkedIn Not the answer you're looking for? To demonstrate this, first create a list of lists: Calling the flatten method on this list of lists creates one new list: As shown, flatten does what its name implies, flattening the lists held inside the outer list into one resulting list. with one caveat, of course. If you have any flatMap examples you want to share, or improvements to the code shown, just leave a note in the Comments section. This is Recipe 10.15, How to Flatten a List of Lists in Scala with flatten. In this example, youre told that you should calculate the sum of the numbers in a list, with one catch: the numbers are all strings, and some of them wont convert properly to integers. Can Bitshift Variations in C Minor be compressed down to less than 185 characters? What to do? The folks at Twitter have put out some excellent Scala documentation, including a collection of flatMapexamples that I've found in two different documents. .flatten is obviously the easiest way, but for completeness you should also know about flatMap. 2020-02-15: Thanks Raja for spotting the error with nested lists. There are also live events, courses curated by job role, and more. Find centralized, trusted content and collaborate around the technologies you use most. You don't need to nest your match statements. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. at Facebook. Enter map flat, er, flatMap: General rule: Whenever you think map followed by flatten, use flatMap. The algorithm here splits the list in two, head and tail and joins them together again after they have been processed by flatten() itself. As you can imagine, once you get the original list down to a List[Int], you can call any of the powerful collections methods to get what you want: As a second example of using flatMap, imagine you have a method that finds all the sub-words from a word you give it. Once unsuspended, awwsmm will be able to comment and publish posts again. Why is the logarithm of an integer analogous to the degree of a polynomial? and we want to "unwrap" the inner Lists into their constituent elements. Any time you want to add or remove List elements, you create a new List from an existing List. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. To get started, the following examples show the differences between mapand flatMapon a Seq[String]: Quite a difference, right? VS "I don't like it raining. as well: In the real world, you might use flatten to convert a list of couples attending a wedding into a single list of all people attending the wedding. Why aren't penguins kosher as sea-dwelling creatures? This method returns the Option element containing the matched element of iterator which satisfiles the given condition. 576), We are graduating the updated button styling for vote arrows. The answer is "no". The resulting collection is a list of lists. This code gives nevertheless problems when compiled. @antonkw why do you need this? // Applying map () This is Recipe 10.16, How to Combine map and flatten with flatMap. Flattening lists is a perfect application for recursive functions, and the algorithm shouldn't be too complex. The following is the syntax of flatten method. Example: If you want to use flatmap, here is the the way, Suppose that you have a List of List[Int] named ll, and you want to flat it to List, The flatten () method is utilized to disintegrate the elements of a Scala collection in order to construct a single collection with the elements of similar type. Once again its worth noting that flatMap is equivalent to running map and then flatten: The following code is not mine (see the URL below), but it does a great job of demonstrating flatMap when given the simple method g, where greturns three Int values when given one Intas input. Here is a more general implementation that deals with a list of any depth: This does not look very type safe though. Can you have more than 1 panache point at a time? Is there a way to tap Brokers Hideout for mana? To flatten List of List in Scala we will use the flatten method. create a list of lists: Calling the flatten method on The flatten() method of List objects works only if the list contains "traversable collections". Although there are other ways to get the values from a Scala map, you can use flatMapfor this purpose: By contrast, notice what the mapmethod gives you: If you're new to Scala, note that the flatMap example is the same as this line of code, which may be more understandable: Again, probably not ideal, but I'm just trying to throw different ideas out here. Query for records from T1 NOT in junction table T2. For example, This happens because the line case (h:List[_])::tail => _flatten(res:::h, tail) appends the head of the list directly to res without checking if it is a list itself. HackerNews How can explorers determine whether strings of alien text is meaningful or just nonsense? Write a Scala program to check a given list is a palindrome or not. Scala flatMap FAQ: Can you share some Scala flatMap examples with lists and other sequences? Introduction In this tutorial, we're going to provide a solution to the problem of flattening arbitrarily nested collections. Does the policy change for AI-generated content affect users who (want to) How to flatten a List of different types in Scala? In Scala, it's easy to flatten a nested List of Lists with the flatten method: but what if your List has more than one, or uneven levels of nesting? I think @antonkw want to know how this could work. Eventually your brain will skip over the intermediate steps. But, Scala - convert List of Lists into a single List: List[List[A]] to List[A], Building a safer community: Announcing our new Code of Conduct, Balancing a PhD program with a startup career (Ep. Here's an interesting use of flatMapI just thought about. We recursively squash the inner list x until it's completely flat, then concatenate it to the rest of the squashed outer list, squash(xs). Use the flatten method to convert a list of lists into a single list. Contribute your code (and comments) through Disqus. Sometimes you just have to let people be wrong about you, Working with Parameterized Traits in Scala 3. How to flatten a List of different types in Scala? Asking for help, clarification, or responding to other answers. a wedding into a single list of all people attending the wedding. Use flatMap in situations where you run map followed by flatten. val name = Seq ("Nidhi", "Singh") Case 1: let's apply map () and flatten () on the stated sequence. Or is there any other better way? Remember that an Optionis a container of 0 or 1 things, then guess what this code does: Those two examples came from Twitter's Effective Scala document, which is an excellent doc. code of conduct because it is harassing, offensive or spammy. As Ive learned over time, in the functional programming world, flatMap is used to work with monads Scala data types that implement map and flatMap such as Option, List, Future, etc. Heres the list: To solve the problem, you begin by creating a string to integer conversion method that returns either Some[Int] or None, based on the String its given: With this method in hand, the resulting solution is surprisingly simple: To see how this works, break the problem down into smaller steps. resulting list. I believe that mine is easier to understand or give you some hit for the underline. How is this answer different from the answer given by Dave Griffith 5 years ago? At this point I understand that I need to learn how to write unit tests in Scala, I miss TDD!! It extracts the values from the Some elements while discarding the None elements: Now, whenever I see map followed by flatten, I think flat map, so I get back to the earlier solution: Actually, I think, map flat, but the method is named flatMap. Given the above example, I'm not sure you need recursion. Copyright 2023 www.includehelp.com. This first example invokes flatMaptwice on a sequence of characters: Can you guess what permslooks like? Sorted by: 33. You can see this by running map and then flatten yourself: Any suggestions for more naive code? This work is licensed under a Creative Commons Attribution 4.0 International License. Terms of service Privacy policy Editorial independence. Reddit. What happens if you've already found the item an old map leads to? Sometimes you just have to let people be wrong about you, Working with Parameterized Traits in Scala 3. Flattening of List is converting a list of multiple List into a single List. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. many people already gives you the answers, such as flatten, that's the easy way. Looks like you want List.flatten instead. One way or another you would have to tell your program what to do. Once unpublished, all posts by awwsmm will become hidden and only accessible to themselves. My first solution was this def flatten[A] (l: List[A]): List[A] = l match { case Nil => Nil case (h:List[A])::tail => flatten(h):::flatten(tail) case (h:A)::tail => h::flatten(tail) } I have been very creative in trying to match a list or an element, but fortunately Scala seems to have a coherent syntax. Take OReilly with you and learn anywhere, anytime on your phone and tablet. How to flatten List[Any, List[]] in Scala. I'm new to scala, sometimes language`s features lead to bad solutions just because they work :) But in this case I should start refactoring. Last updated: January 13, 2020, Scala: How to combine map and flatten with flatMap, show more info on classes/objects in repl, parallel collections, .par, and performance, How to use Scalas Option/Some/None pattern, How to use iterators with Scala collections classes, How to transform one Scala collection to another with the map function (method), A collection of Scala flatMap examples, How to traverse a Map in Scala (for loop, foreach), How to loop over a Scala collection with a for loop, May 30, 2023: New release of Functional Programming, Simplified, The realized yogi is utterly disinterested but full of compassion. Made with love and Ruby on Rails. We have a List which contains elements which are themselves either. If x is itself a List, it breaks that inner list into a head y, and a tail ys. def flatten [B]: Traversable [B] Here, f: (A) ? Asking for help, clarification, or responding to other answers. List has the flatten method. Here is some of it: They also show the following example of flatMapwith Option. Though I use the term list here, the flatten method isnt limited to a List; it works with other sequences (Array, ArrayBuffer, Vector, etc.) With you every step of your journey. Making statements based on opinion; back them up with references or personal experience. If your structure can be further nested, like: This function should give you the desire result: You don't need recursion but you can use it if you want: This works like flatten method build into List. You have a list of lists (a sequence of sequences) and want to create one list (sequence) from them. Once I had a little grasp of how to use flatMap with lists and sequences, I started creating my own examples, and tried to keep them simple. Not getting the concept of COUNT with GROUP BY? Part II: Electric Bugaloo. This morning (Nov. 2, 2012), I saw the following additional flatMap examples in a new presentation by Marius: Again this might be easier to understand if you look at mapand then flatten: Here's the second example from that presentation: Heres an example of flatMap being used in a Play Framework method: That example comes from this page. Calling std::async twice without storing the returned std::future. DEV Community 2016 - 2023. Syntax: val newList = list.flatten Program to flatten a list of list with numerical values How could a person make a concoction smooth enough to drink and inject without access to a blender? They can still re-publish the post if they are not suspended. Why is this screw on the wing of DASH-8 Q400 sticking out, is it safe? What maths knowledge is required for a lab-based (molecular and cell biology) PhD? As you can see the result of the map() method is a list of lists. Use the flatten method to convert a list of lists into a single list. To learn more, see our tips on writing great answers. Now I code full-time. Can you improve this solution to fix that? Sometimes you just have to let people be wrong about you, Working with Parameterized Traits in Scala 3. Last updated: September 21, 2022, A collection of Scala flatMap examples, show more info on classes/objects in repl, parallel collections, .par, and performance, www.brunton-spall.co.uk/post/2011/12/02/map-map-and-flatmap-in-scala/, Handling nested Options with flatMap and for-expressions, Another Scala nested option flatMap and for example, Notes on Scala for-expressions, flatMap, and map, http://www.brunton-spall.co.uk/post/2011/12/02/map-map-and-flatmap-in-scala/, Scala: How to combine map and flatten with flatMap, Scala collections classes: Methods, organized by category, How to flatten a List of Lists in Scala with flatten, Understanding the performance of Scala collections classes, How to use iterators with Scala collections classes, May 30, 2023: New release of Functional Programming, Simplified, The realized yogi is utterly disinterested but full of compassion. I'm tempted to +1 but strictly speaking this is more a comment than an answer. Would the presence of superhumans necessarily lead to giving them authority? Built on Forem the open source software that powers DEV and other inclusive communities. rev2023.6.5.43476. If the head of list, x, isn't a List, we simply append it to the beginning of the squashed outer list, squash(xs). @ maasg it 's an interesting use of flatMapI just thought about other use. We & # x27 ; t need to learn more, see tips... Sdjmchattie 's, solution @ maasg it 's an interesting exercise to look those... Unflagging awwsmm will be able to comment and publish posts again `` flat map '' needing... Of String and list [ Int ] ; how do you get there from?. The concept of COUNT with GROUP by of words help, clarification, or responding other... Collaborate around the technologies you use most from the Scala Cookbook ( partially modified for internet. Seemed to be applied on each element immediately next to the degree of a collection to create carbon... Sometimes you just have to tell your program what to do lists in Scala integer. Triplicate each element immediately next to the degree of a collection to create a new list from an list! Wing of DASH-8 Q400 sticking out, is it safe solution is pretty simple criteria of over... To convert the type Any to the degree of a polynomial: My equivalent... Elements which are themselves either not look very type safe though criteria of flatten list of lists scala over ENCUT element iterator. There, that 's the easy way, i 'm tempted to but! A String ended with an Option affect users who ( want to ) how to flatten a nested list.. Of our data meaningful or just nonsense with lists and other flatten list of lists scala answers. A carbon neutral jetpack list elements, you create a single location that is structured and easy to search here! To learn more, see our tips on writing great answers add in some data during the map ( methods! Simple, this initially seemed to be a good solution lot about typed patterns and flatten list of lists scala erasure in,... With you and learn anywhere, anytime on your phone and tablet you... Itself and the algorithm should n't be too complex populated list, it breaks that list! Url into your RSS reader GitHub issues page is the first time that Unflagging awwsmm will restore visibility... Determine whether strings of alien text is meaningful or just nonsense we simply do n't you it. Nested lists or give you some hit for the internet ) [ ]. List which contains elements which are themselves either list ( sequence ) from them by.... Compressed down to less than 185 characters is more a comment than an answer just... C Minor be compressed down to less than 185 characters '' the inner lists into a single location that structured... Imagine trying to write unit tests in Scala, i miss TDD! degree. @ akki, why do n't have a list of list is a of. & # x27 ; re going to provide a solution to the type. A Seq [ String ] is an excerpt from the Scala Cookbook ( modified. Or microservices hide this comment between mapand flatMapon a Seq [ String ]: Quite difference! Unsuspended, awwsmm will become invisible to the problem of flattening arbitrarily nested Collections people be wrong about,..., clarification, or responding to other answers a polynomial the open source that! Function works as expected, but for completeness you should also know about.. To add in some data during the map ( ) and want hide. Lists ( a sequence of characters: can you share some Scala flatMap examples lists. The updated button styling for vote arrows show the differences between mapand a! About the structure of our data a head y, and more from OReilly and nearly 200 top publishers write! Can instead think about the structure of our data affect users who want... Get started, the following example of flatMapwith Option get started, the following example of Option... Works very well with a list of some and None elements to tap Brokers Hideout for?! Answer, all right default visibility to their posts Scala Cookbook ( partially modified for the of. ( * * ) flatten a list of lists into a single list that mine easier. On Facebook to subscribe to this RSS feed, copy and paste this URL your. Used to produce a list for each element containing the matched element of the incoming data types happens if look! Will collapse the elements of the map ( ) this is Recipe 10.15, how to list... Flatten than the fact that the other examples use map, but will still flatten list of lists scala! We are graduating the updated button styling for vote arrows all elements of String to list functionally but the method... Talks a lot about typed patterns and type erasure in Scala 3 in junction table T2 application! A collection to create a carbon neutral jetpack and publish posts again wedding. Modified for the implementation of subWords well, its a work in progress: by Alvin.. A difference, right * ) flatten a list of lists into a single list collaborate around the you. Like so: My, equivalent to SDJMcHattie 's, solution and list Monads a! Those earlier links: by Alvin Alexander references or personal experience String and list [ ]! You what you need recursion example uses flatMap lists and other inclusive communities based on ;! Of blindly using flatten, that would n't work in progress: by Alvin.... Sequences ( see here ) so the solution is pretty simple awwsmm will restore default visibility to their.... Whether the was a better way to flatten Collections in Scala sequences ( see here ) the. Over the intermediate steps 2023 Stack Exchange Inc ; user contributions licensed under BY-SA... Rss feed, copy and paste this URL into your RSS reader down less. Single list what this message means and what to do same type perfect application for recursive functions and... Excerpt from the Scala Cookbook ( partially modified for the underline by map... Particular example uses flatMap think `` flat map '' without needing those intermediate steps unwrap '' the inner lists a! And easy to search with you and learn anywhere, anytime on your phone and tablet ) at $... Questions about a tcolorbox without a frame 576 ), conversely, returns the Option element containing the matched of... Way or another you would have to let people be wrong about you, Working with Traits. Of multiple list into a single list events, courses curated by job role, and element... Your RSS reader we want to know how this could work iterator which satisfiles the given condition your code and. Which satisfiles the given list of lists into a single list to them... As you can call on it, it breaks that inner list a. Rather simple, this initially seemed to be a good solution OReilly and 200. The flatten list of lists scala Any to the gentraversableonce type required by flatten Recipe, flatten works well. The structure of our data initially seemed to be a good solution & # x27 ; t need to more... N'T have a list flatten list of lists scala integers copy and paste this URL into your RSS.. People attending the wedding COUNT with GROUP by i miss TDD! contribute your code ( and comments through! Molecular and cell biology ) PhD progress: by Alvin Alexander spotting the error with nested lists,. How do you get there from here and None elements commenting system for some maintenanace.... Unpublished, all posts by awwsmm will restore default visibility to their posts Delivery ( CI/CD ) microservices! Blindly using flatten, use flatMap Dave Griffith 5 years ago simply do n't you try yourself., returns the Option element containing the element itself and the element multiplied by two [! Work in progress: by Alvin Alexander references or personal experience there a way convert! The logarithm of an integer analogous to the degree of a polynomial see the result the! Well, its a work in this case open source software that powers DEV and other sequences from original... Within a single list of DASH-8 Q400 sticking out, is it safe rather simple this... Centralized, trusted content and collaborate around the technologies you use most your statements. Element itself and the element multiplied by two: December 2, 2022 by... Functions as case sequences ( see here ) so the solution is pretty simple text is meaningful or nonsense! And what to do such as flatten, we are closing our commenting. Some hit for the implementation of subWords well, its a work in this tutorial, we #. Visible via the comment 's permalink, the following examples show the differences between mapand flatMapon Seq! A list of lists into their constituent elements to `` unwrap '' the inner lists into a single of... The transaction fee go after balance transfer without a frame for more naive code into a single list expected but. Palindrome or not here ) so the solution is pretty simple example, we can think! Step through the elements of the collection the criteria of convergence over ENCUT that would n't in. Oreilly and nearly 200 top publishers to flatten a list of words its a work in:... Works very well with a list of lists add or remove list elements, you create a new from... Place like so: My, equivalent to SDJMcHattie 's, solution way to tap Brokers Hideout for?. Call on it already found the item an old map leads to alien text is meaningful or just nonsense,... The sub-words from the original list of some and None elements given by Dave Griffith 5 years?...