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• Subset a data.frame by list and apply function on each part, by rows

  - by aL3xa

  This may seem as a typical plyr problem, but I have something different in mind. Here's the function that I want to optimize (skip the for loop). # dummy data set.seed(1985) lst <- list(a=1:10, b=11:15, c=16:20) m <- matrix(round(runif(200, 1, 7)), 10) m <- as.data.frame(m) dfsub <- function(dt, lst, fun) { # check whether dt is `data.frame` stopifnot (is.data.frame(dt)) # check if vectors in lst are "whole" / integer # vector elements should be column indexes is.wholenumber <- function(x, tol = .Machine$double.eps^0.5) abs(x - round(x)) < tol # fall if any non-integers in list idx <- rapply(lst, is.wholenumber) stopifnot(idx) # check for list length stopifnot(ncol(dt) == length(idx)) # subset the data subs <- list() for (i in 1:length(lst)) { # apply function on each part, by row subs[[i]] <- apply(dt[ , lst[[i]]], 1, fun) } # preserve names names(subs) <- names(lst) # convert to data.frame subs <- as.data.frame(subs) # guess what =) return(subs) } And now a short demonstration... actually, I'm about to explain what I primarily intended to do. I wanted to subset a data.frame by vectors gathered in list object. Since this is a part of code from a function that accompanies data manipulation in psychological research, you can consider m as a results from personality questionnaire (10 subjects, 20 vars). Vectors in list hold column indexes that define questionnaire subscales (e.g. personality traits). Each subscale is defined by several items (columns in data.frame). If we presuppose that the score on each subscale is nothing more than sum (or some other function) of row values (results on that part of questionnaire for each subject), you could run: > dfsub(m, lst, sum) a b c 1 46 20 24 2 41 24 21 3 41 13 12 4 37 14 18 5 57 18 25 6 27 18 18 7 28 17 20 8 31 18 23 9 38 14 15 10 41 14 22 I took a glance at this function and I must admit that this little loop isn't spoiling the code at all... BUT, if there's an easier/efficient way of doing this, please, let me know!

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• std::list iterator: get next element

  - by sheepsimulator

  I'm trying to build a string using data elements stored in a std::list, where I want commas placed only between the elements (ie, if elements are {A,B,C,D} in list, result string should be "A,B,C,D". This code does not work: typedef std::list< shared_ptr<EventDataItem> > DataItemList; // ... std::string Compose(DataItemList& dilList) { std::stringstream ssDataSegment; for(iterItems = dilList.begin(); iterItems != dilList.end(); iterItems++) { // Lookahead in list to see if next element is end if((iterItems + 1) == dilList.end()) { ssDataSegment << (*iterItems)->ToString(); } else { ssDataSegment << (*iterItems)->ToString() << ","; } } return ssDataSegment.str(); } How do I get at "the-next-item" in a std::list using an iterator? I would expect that it's a linked-list, why can't I get at the next item?

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• std::list : get next element

  - by sheepsimulator

  I'm trying to build a string using data elements stored in a std::list, where I want commas placed only between the elements (ie, if elements are {A,B,C,D} in list, result string should be "A,B,C,D". This code does not work: typedef std::list< shared_ptr<EventDataItem> > DataItemList; // ... std::string Compose(DataItemList& dilList) { std::stringstream ssDataSegment; for(iterItems = dilList.begin(); iterItems = dilList.end(); iterItems++) { // Lookahead in list to see if next element is end if((iterItems + 1) == dilList.end()) { ssDataSegment << (*iterItems)->ToString(); } else { ssDataSegment << (*iterItems)->ToString() << ","; } } return ssDataSegment.str(); } How do I get at "the-next-item" in a std::list using an iterator? I would expect that it's a linked-list, why can't I get at the next item?

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• C# Changing Objects within a List

  - by kwong22

  Hi, I'm having a little problem changing members of an object in a list using a found index. So this is the method I am currently working with: static void addToInventory(ref List<baseItem> myArray, baseItem item, float maxAmount, ref float currentAmount) { if (currentAmount + item.getWeight() <= maxAmount) { Console.WriteLine("item.Quantity = {0}", item.Quantity); if (myArray.Contains(item)) { Console.WriteLine("Item ({0}) already exists", item.Name); int id = myArray.IndexOf(item); myArray[id].Quantity += item.Quantity;//Change occurs in this line, item.Quantity becomes the same as myArray[id].Quantity } else { Console.WriteLine("Adding new item ({0})", item.Name); myArray.Add(item); } currentAmount += item.getWeight(); } else { Console.WriteLine("Inventory full"); } myArray.Sort(); } This method takes several parameters including the inventory/list. I check if the item fits in and if it does, I see if there is another item of the same name in the list, find the index, and add more of the item. However, the quantity of the item added suddenly becomes the same as the quantity of the item in the list. For some reason, this also changes the quantity of the item outside of the list. So therefore, instead of quantities adding up like this: 1, 2, 3, 4, they add up like this: 1, 2, 4, 8. I've just started to learn how to use lists so if there is anything I'm missing, don't hesitate to criticize. Thanks in advance.

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• List modification in Python

  - by user2945143

  We are given an algorithm to modify a list of numbers from 1 to 28. There are 5 steps in the algorithm. We have written functions for each step (all correct). We need to write a function that combines all 5 steps. The algorithm modifies the list to get a value. Each time you get a new value, you use the list created by the algorithm from the previous step. This is what we have gotten so far for the code: get_card_at_top_index(insert_top_to_bottom(triple_cut((move_joker_2( move_joker_1(deck)))))) When we run the code to generate the get_card_at_top_index, the first answer is correct. However, the rest are not. Instead of using from the new list, python uses the value that it generated from the last step. What did we do wrong? UPDATE: The other 5 codes passed the tests, they are correct. Code 1 (List) = list1 Code 2 (list1) = list2 Code 3 (list2) = list3 Code 4 (list3) = list4 Code 5 (list4) = list5 we generate a number from 5. We need to run the algorithm again to generate 25 more numbers. We will use list 5 start from step 1

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• F# insert/remove item from list

  - by Timothy

  How should I go about removing a given element from a list? As an example, say I have list ['A'; 'B'; 'C'; 'D'; 'E'] and want to remove the element at index 2 to produce the list ['A'; 'B'; 'D'; 'E']? I've already written the following code which accomplishes the task, but it seems rather inefficient to traverse the start of the list when I already know the index. let remove lst i = let rec remove lst lst' = match lst with | [] -> lst' | h::t -> if List.length lst = i then lst' @ t else remove t (lst' @ [h]) remove lst [] let myList = ['A'; 'B'; 'C'; 'D'; 'E'] let newList = remove myList 2 Alternatively, how should I insert an element at a given position? My code is similar to the above approach and most likely inefficient as well. let insert lst i x = let rec insert lst lst' = match lst with | [] -> lst' | h::t -> if List.length lst = i then lst' @ [x] @ lst else insert t (lst' @ [h]) insert lst [] let myList = ['A'; 'B'; 'D'; 'E'] let newList = insert myList 2 'C'

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• Bounding volume hierarchy - linked nodes (linear model)

  - by teodron

  The scenario A chain of points: (Pi)i=0,N where Pi is linked to its direct neighbours (Pi-1 and Pi+1). The goal: perform efficient collision detection between any two, non-adjacent links: (PiPi+1) vs. (PjPj+1). The question: it's highly recommended in all works treating this subject of collision detection to use a broad phase and to implement it via a bounding volume hierarchy. For a chain made out of Pi nodes, it can look like this: I imagine the big blue sphere to contain all links, the green half of them, the reds a quarter and so on (the picture is not accurate, but it's there to help understand the question). What I do not understand is: How can such a hierarchy speed up computations between segments collision pairs if one has to update it for a deformable linear object such as a chain/wire/etc. each frame? More clearly, what is the actual principle of collision detection broad phases in this particular case/ how can it work when the actual computation of bounding spheres is in itself a time consuming task and has to be done (since the geometry changes) in each frame update? I think I am missing a key point - if we look at the picture where the chain is in a spiral pose, we see that most spheres are already contained within half of others or do intersect them.. it's odd if this is the way it should work.

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• MVC: How to Implement Linked Views?

  - by cw'

  I'm developing a java application to visualize time series. I need (at least) three linked views, meaning that interaction with one of them updates the others. The views are: A list represents the available and currently selected time series. The selected time series are used as input for subsequent computations. Changing the selection should update the other views. A line chart displays the available and selected time series. Time series should be selectable from here by clicking on them. A bar chart shows aggregated data on time series. When zooming in to a period of time, the line chart should zoom in to the same period (and vice versa). How to implement this nicely, from a software engineering point of view? I.e. I'd like to write reusable and clear, maintainable code. So I thought of the MVC pattern. At first I liked the idea of having the three view components observing my model class and to refresh views upon being notified. But then, it didn't feel right to store view related data in the model. Storing e.g. the time series selection or plot zoom level in the model makes implications about the view which I wouldn't want in a reusable model. On the other hand, having the controllers observe each other results in a lot of dependencies. When adding another view, I'd have to register all other views as observer of the new view and vice versa, passing around many references and introducing dependencies. Maybe another "model" storing only view-related data would be the solution?

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• Convert List of one type to Array of another type using Dozer

  - by aheu

  I'm wondering how to convert a List of one type to an array of another type in Java using Dozer. The two types have all the same property names/types. For example, consider these two classes. public class A{ private String test = null; public String getTest(){ return this.test } public void setTest(String test){ this.test = test; } } public class B{ private String test = null; public String getTest(){ return this.test } public void setTest(String test){ this.test = test; } } I've tried this with no luck. List<A> listOfA = getListofAObjects(); Mapper mapper = DozerBeanMapperSingletonWrapper.getInstance(); B[] bs = mapper.map(listOfA, B[].class); I've also tried using the CollectionUtils class. CollectionUtils.convertListToArray(listOfA, B.class) Neither are working for me, can anyone tell me what I am doing wrong? The mapper.map function works fine if I create two wrapper classes, one containing a List and the other a b[]. See below: public class C{ private List<A> items = null; public List<A> getItems(){ return this.items; } public void setItems(List<A> items){ this.items = items; } } public class D{ private B[] items = null; public B[] getItems(){ return this.items; } public void setItems(B[] items){ this.items = items; } } This works oddly enough... List<A> listOfA = getListofAObjects(); C c = new C(); c.setItems(listOfA); Mapper mapper = DozerBeanMapperSingletonWrapper.getInstance(); D d = mapper.map(listOfA, D.class); B[] bs = d.getItems(); How do I do what I want to do without using the wrapper classes (C & D)? There has got to be an easier way... Thanks!

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• No Matching Function Error for inserting into a list in c++

  - by Josh Curren

  I am getting an error when I try to insert an item into a list (in C++). The error is that there is no matching function for call to the insert(). I also tried push_front() but got the same error. Here is the error message: main.cpp:38: error: no matching function for call to ‘std::list<Salesperson, std::allocator<Salesperson> >::insert(Salesperson&)’ /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/list.tcc:99: note: candidates are: std::_List_iterator<_Tp> std::list<_Tp, _Alloc>::insert(std::_List_iterator<_Tp>, const _Tp&) [with _Tp = Salesperson, _Alloc = std::allocator<Salesperson>] /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_list.h:961: note: void std::list<_Tp, _Alloc>::insert(std::_List_iterator<_Tp>, size_t, const _Tp&) [with _Tp = Salesperson, _Alloc = std::allocator<Salesperson>] Here is the code: #include <stdlib.h> #include <iostream> #include <fstream> #include <string> #include <list> #include "Salesperson.h" #include "Salesperson.cpp" #include "OrderedList.h" #include "OrderedList.cpp" using namespace std; int main(int argc, char** argv) { cout << "\n------------ Asn 8 - Sales Report ------------" << endl; list<Salesperson> s; int id; string fName, lName; int numOfSales; string year; std::ifstream input("Sales.txt"); while( !std::getline(input, year, ',').eof() ) { input >> id; input >> lName; input >> fName; input >> numOfSales; Salesperson sp = Salesperson( id, fName, lName ); s.insert( sp ); //THIS IS LINE 38 ************************** for( int i = 0; i < numOfSales; i++ ) { double sale; input >> sale; sp.sales.insert( sale ); } } cout << endl; return (EXIT_SUCCESS); }

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• C++ linked list based tree structure. Sanely move nodes between lists.

  - by krunk

  The requirements: Each Node in the list must contain a reference to its previous sibling Each Node in the list must contain a reference to its next sibling Each Node may have a list of child nodes Each child Node must have a reference to its parent node Basically what we have is a tree structure of arbitrary depth and length. Something like: -root(NULL) --Node1 ----ChildNode1 ------ChildOfChild --------AnotherChild ----ChildNode2 --Node2 ----ChildNode1 ------ChildOfChild ----ChildNode2 ------ChildOfChild --Node3 ----ChildNode1 ----ChildNode2 Given any individual node, you need to be able to either traverse its siblings. the children, or up the tree to the root node. A Node ends up looking something like this: class Node { Node* previoius; Node* next; Node* child; Node* parent; } I have a container class that stores these and provides STL iterators. It performs your typical linked list accessors. So insertAfter looks like: void insertAfter(Node* after, Node* newNode) { Node* next = after->next; after->next = newNode; newNode->previous = after; next->previous = newNode; newNode->next = next; newNode->parent = after->parent; } That's the setup, now for the question. How would one move a node (and its children etc) to another list without leaving the previous list dangling? For example, if Node* myNode exists in ListOne and I want to append it to listTwo. Using pointers, listOne is left with a hole in its list since the next and previous pointers are changed. One solution is pass by value of the appended Node. So our insertAfter method would become: void insertAfter(Node* after, Node newNode); This seems like an awkward syntax. Another option is doing the copying internally, so you'd have: void insertAfter(Node* after, const Node* newNode) { Node *new_node = new Node(*newNode); Node* next = after->next; after->next = new_node; new_node->previous = after; next->previous = new_node; new_node->next = next; new_node->parent = after->parent; } Finally, you might create a moveNode method for moving and prevent raw insertion or appending of a node that already has been assigned siblings and parents. // default pointer value is 0 in constructor and a operator bool(..) // is defined for the Node bool isInList(const Node* node) const { return (node->previous || node->next || node->parent); } // then in insertAfter and friends if(isInList(newNode) // throw some error and bail I thought I'd toss this out there and see what folks came up with.

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• Hibernate Query for a List of Objects that matches a List of Objects' ids

  - by sal

  Given a classes Foo, Bar which have hibernate mappings to tables Foo, A, B and C public class Foo { Integer aid; Integer bid; Integer cid; ...; } public class Bar { A a; B b; C c; ...; } I build a List fooList of an arbitrary size and I would like to use hibernate to fetch List where the resulting list will look something like this: Bar[1] = [X1,Y2,ZA,...] Bar[2] = [X1,Y2,ZB,...] Bar[3] = [X1,Y2,ZC,...] Bar[4] = [X1,Y3,ZD,...] Bar[5] = [X2,Y4,ZE,...] Bar[6] = [X2,Y4,ZF,...] Bar[7] = [X2,Y5,ZG,...] Bar[8] = ... Where each Xi, Yi and Zi represents a unique object. I know I can iterate fooList and fetch each List and call barList.addAll(...) to build the result list with something like this: List<bar> barList.addAll(s.createQuery("from Bar bar where bar.aid = :aid and ... ") .setEntity("aid", foo.getAid()) .setEntity("bid", foo.getBid()) .setEntity("cid", foo.getCid()) .list(); ); Is there any easier way, ideally one that makes better use of hibernate and make a minimal number of database calls? Am I missing something? Is hibernate not the right tool for this?

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• how to bind a list to a dropdown list in gridview

  - by user3721173

  I have a GridView that it contain a Drop-down list.I have a list that wanna to bind this list to drop-down in gridview. <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"OnSelectedIndexChanged="GridView1_SelectedIndexChanged" OnRowDataBound="GridView1_RowDataBound"> <Columns> <ItemTemplate> <asp:Label ID="Label2" runat="server"></asp:Label> <asp:DropDownList ID="DropDownList3" runat="server" AppendDataBoundItems="True" OnSelectedIndexChanged="DropDownList3_SelectedIndexChanged1" > </asp:DropDownList> </ItemTemplate> </asp:TemplateField> </Columns> and protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) { DropDownList dropdown = (DropDownList)e.Row.FindControl("DropDownList3"); ClassDal obj = new ClassDal(); List<phone> list = obj.GetAll(); dropdown.DataTextField = "phone"; dropdown.DataValueField = "id"; dropdown.DataSource = list.ToList(); dropdown.DataBind(); } and namespace sample_table { public class ClassDal { public List<phone> GetAll() { using (PracticeDBEntities1 context = new PracticeDBEntities1()) { return context.phone.ToList(); } } } } but i received this exception :Object reference not set to an instance of an object on the row: dropdown.DataTextField = "phone";

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• Mailing List Solution

  - by Shoaibi

  I have more than 1M users and i need to send newsletters to. I have tried PHPList but it has failed as it gets stalled every 30K emails. I need a faster and more reliable solution.

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• Procmail Mailing List (With Access Control)

  - by bradlis7

  This seems like it should be fairly easy to do, but I've run into a few problems. I've added a cron job to parse all users whose UID is greater than 5000: * * * * * root /usr/bin/test /etc/passwd -nt ~allusers/.forward \ && /bin/egrep '([5-9]|[0-9]{2})[0-9]{3}' /etc/passwd | /bin/grep -v 65534 \ | /bin/cut -d ':' -f 1 > ~allusers/.forward Then I created a .procmailrc file: VERBOSE=yes LOGFILE=/var/log/procmailrc #Allow only certain users to send :0 * ^From.*[email protected].* {} :0E /dev/null But, the .forward file is processed before it even gets to procmail, evidently. If I moved the .forward file to another filename, can I use it in procmail to send an email to the users in this file?

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• List<> capacity has more items than added.

  - by Pete

  List <string> ali = new List<string>(); ali.Clear(); ali.Add("apple"); ali.Add("orange"); ali.Add("banana"); ali.Add("cherry"); ali.Add("mango"); ali.Add("plum"); ali.Add("jackfruit"); Console.WriteLine("the List has {0} items in it.",ali.Capacity.ToString()); when I run this the Console displays: the List has 8 items in it. I don't understand why its showing a capacity of 8, when I only added 7 items.

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• LIST<> AddRange throwing ArgumentException

  - by Tim

  Hi all, I have a particular method that is occasionally crashing with an ArgumentException: Destination array was not long enough. Check destIndex and length, and the array's lower bounds.: at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable) at System.Collections.Generic.List`1.CopyTo(T[] array, Int32 arrayIndex) at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection) at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection) The code that is causing this crash looks something like this: List<MyType> objects = new List<MyType>(100); objects = FindObjects(someParam); objects.AddRange(FindObjects(someOtherParam); According to MSDN, List<.AddRange() should automatically resize itself as needed: If the new Count (the current Count plus the size of the collection) will be greater than Capacity, the capacity of the List<(Of <(T)) is increased by automatically reallocating the internal array to accommodate the new elements, and the existing elements are copied to the new array before the new elements are added. Can someone think of a circumstance in which AddRange could throw this type of exception?

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• Advanced Python list comprehension

  - by Yuval A

  Given two lists: chars = ['ab', 'bc', 'ca'] words = ['abc', 'bca', 'dac', 'dbc', 'cba'] how can you use list comprehensions to generate a filtered list of words by the following condition: given that each word is of length n and chars is of length n as well, the filtered list should include only words that each i-th character is in the i string in words. In this case, we should get ['abc', 'bca'] as a result. (If this looks familiar to anyone, this was one of the questions in the previous Google code jam)

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• Efficient intersection of two List<String> in Java?

  - by Pentium10

  Question is simple: I have two List List<String> columnsOld = DBUtils.GetColumns(db, TableName); List<String> columnsNew = DBUtils.GetColumns(db, TableName); And I need to get the intersection of these. Is there a quick way to achieve this?

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• Python: Slicing a list into n nearly-equal-length partitions

  - by Drew

  I'm looking for a fast, clean, pythonic way to divide a list into exactly n nearly-equal partitions. partition([1,2,3,4,5],5)->[[1],[2],[3],[4],[5]] partition([1,2,3,4,5],2)->[[1,2],[3,4,5]] (or [[1,2,3],[4,5]]) partition([1,2,3,4,5],3)->[[1,2],[3,4],[5]] (there are other ways to slice this one too) There are several answers in here http://stackoverflow.com/questions/1335392/iteration-over-list-slices that run very close to what I want, except they are focused on the size of the list, and I care about the number of the lists (some of them also pad with None). These are trivially converted, obviously, but I'm looking for a best practice. Similarly, people have pointed out great solutions here http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks-in-python for a very similar problem, but I'm more interested in the number of partitions than the specific size, as long as it's within 1. Again, this is trivially convertible, but I'm looking for a best practice.

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• Equals method of System.Collections.Generic.List<T>...?

  - by Sambo

  I'm creating a class that derives from List... public class MyList : List<MyListItem> {} I've overridden Equals of MyListItem... public override bool Equals(object obj) { MyListItem li = obj as MyListItem; return (ID == li.ID); // ID is a property of MyListItem } I would like to have an Equals method in the MyList object too which will compare each item in the list, calling Equals() on each MyListItem object. It would be nice to simply call... MyList l1 = new MyList() { new MyListItem(1), new MyListItem(2) }; MyList l2 = new MyList() { new MyListItem(1), new MyListItem(2) }; if (l1 == l2) { ... } ...and have the comparisons of the list done by value. What's the best way...?

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• List problem in Reporting Services 2005

  - by Kris

  Hi, I have a problem with a list in srss 2005. The list is grouping too much information and I dont know how to un-group it. I made a picture to show it. But because I'm new, I can only show it with this link: http://img32.imageshack.us/img32/6058/listproblem.gif So the list is also grouping the weeks, but that is not what I would like. Does anyone know how to change this? (in the designer view) Thanks in advance, Kris

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• F# Active Pattern List.filter or equivalent

  - by akaphenom

  I have a records of types type tradeLeg = { id : int ; tradeId : int ; legActivity : LegActivityType ; actedOn : DateTime ; estimates : legComponents ; entryType : ShareOrDollarBased ; confirmedPrice: DollarsPerShare option; actuals : legComponents option ; type trade = { id : int ; securityId : int ; ricCode : string ; tradeActivity : TradeType ; enteredOn : DateTime ; closedOn : DateTime ; tradeLegs : tradeLeg list ; } Obviously the tradeLegs are a type off of a trade. A leg may be settled or unsettled (or unsettled but price confirmed) - thus I have defined the active pattern: let (|LegIsSettled|LegIsConfirmed|LegIsUnsettled|) (l: tradeLeg) = if Helper.exists l.actuals then LegIsSettled elif Helper.exists l.confirmedPrice then LegIsConfirmed else LegIsUnsettled and then to determine if a trade is settled (based on all legs matching LegIsSettled pattern: let (|TradeIsSettled|TradeIsUnsettled|) (t: trade) = if List.exists ( fun l -> match l with | LegIsSettled -> false | _ -> true) t.tradeLegs then TradeIsSettled else TradeIsUnsettled I can see some advantages of this use of active patterns, however i would think there is a more efficient way to see if any item of a list either matches (or doesn't) an actie pattern without having to write a lambda expression specifically for it, and using List.exist. Question is two fold: is there a more concise way to express this? is there a way to abstract the functionality / expression (fun l - match l with | LegIsSettled - false | _ - true) Such that let itemMatchesPattern pattern item = match item with | pattern -> true | _ -> false such I could write (as I am reusing this design-pattern): let curriedItemMatchesPattern = itemMatchesPattern LegIsSettled if List.exists curriedItemMatchesPattern t.tradeLegs then TradeIsSettled else TradeIsUnsettled Thoughts?

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• Write a list class where the only data structure available is a stack

  - by Mike

  Write a list class where the only data structure available is a stack

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• Racket: change dotted pair to list

  - by user2963128

  I have a program that recursively calls a hashtable and prints out data from it. Unfortunately my hashtable seems to be saving data as dotted pairs so when I call the hashtable I get an error saying that there is no data for it because its tryign to search the hashtable for a dotted pair instead of a list. Is there an easy way to make the dotted pair into a regular list? IE im getting '("was" . "beginning") instead of '("was" "beginning") Is there a way to change this without re-writing how my hashtable store stuff? im using the let function to set a variable to this and then calling another function based on this variable (let ((data ( list-ref(hash-ref Ngram-table key) (random (length (hash-ref Ngram-table key)))))) is there a way to make the value stored in data just a list like this '("var1" "var2") instead of a dotted pair? edit: im getting dotted pairs because im using let to set data to the part of the hashtable's key and one of the elements in that hash.

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