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  • How you would you describe the Observer pattern in beginner language?

    - by Sheldon
    Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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  • How to define a varying length of the string in XSD pattern?

    - by infant programmer
    The input XML tag must be validated for a pattern which is like this: type : positive int / decimal, minimum length is 0, max length is 12(before decimal point), fraction digits are optional if exist then precision must be 2. This means both positive integer and Decimal numbers(2 digit precision) are allowed. so the acceptable values can be like, null, 0, 0.00, 1234567890, 123456789012, 123456789012.12, invalid values are: 0.000, 1234567890123(13 digits - invalid), The pattern I have designed is: <xs:pattern value="|([0-9]){12}|([0-9]){12}[.][0-9][0-9]"/> The problem with this pattern is, it doesn't allow the number with string-length less than 12, it says "1234567890" is an invalid value, where as it must be allowed!

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  • Service Layer Pattern - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demonstrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • Is this physical collection class that contains only static methods an Anti-Pattern?

    - by Tj Kellie
    I'm trying to figure out if I should continue on with a current pattern in an application I'm working in, or refactor this into something else. I have a set of collection classes off a generic base of List. These classes have public constructors but contain only static methods that return collections. They look like this: public class UserObjCollection : BaseCollection<UserObj> { public static UserObjCollection GetAllUserObj() { UserObjCollection obj = new UserObjCollection(); obj.MapObjects(new UserObjDataService().GetAllUserObj()); return obj; } } Is this a Pattern or Anti-Pattern and what are the merits of this over a straight factory pattern?

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  • Understanding Service Compensation part of Industrial SOA series

    - by JuergenKress
    Some of the most important SOA design patterns that we have successfully applied in projects will be described in this article. These include the Compensation pattern and the UI mediator pattern, the Common Data Format pattern and the Data Access pattern. All of these patterns are included in Thomas Erl's book, "SOA Design Patterns", and are presented here in detail, together with our practical experiences. We begin our "best of" SOA pattern collection with the Compensation pattern. Compensation is required in error situations in an SOA, as multiple atomic service operations cannot generally be linked with classic transactions this would violate the principle of loose coupling. An error situation of this sort will occur, particularly if service operations are combined into processes or new services during orchestration or by applying the Composite pattern, and the transaction bracket has to be expanded as a result. We need mechanisms to undo the effects of individual services (the status changes in the overall system) and to ensure that a consistent system state is maintained at all times, so as to preserve system integrity. For the Compensation pattern, we would like to address the following questions: Why is compensation important in relation to SOA? How is the topic of compensation linked with the topic of transactions? What are the challenges with regard to compensation... Read the full article in the Service Technology Magazine or at OTN. Share your comments and feedback on the Industrial SOA series by using the hashtag #industrialsoa. Missed an article of the Industrial SOA series visit the overview at OTN. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Facebook Wiki Mix Forum Technorati Tags: Industrial SOA,SOA,SOA Service Compensation,Community,Oracle SOA,Oracle BPM,OPN,Jürgen Kress

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  • How to compile a C++ source code written for Linux/Unix on Windows Vista (code given)

    - by HTMZ
    I have a c++ source code that was written in linux/unix environment by some other author. It gives me errors when i compile it in windows vista environment. I am using Bloodshed Dev C++ v 4.9. please help. #include <iostream.h> #include <map> #include <vector> #include <string> #include <string.h> #include <strstream> #include <unistd.h> #include <stdlib.h> using namespace std; template <class T> class PrefixSpan { private: vector < vector <T> > transaction; vector < pair <T, unsigned int> > pattern; unsigned int minsup; unsigned int minpat; unsigned int maxpat; bool all; bool where; string delimiter; bool verbose; ostream *os; void report (vector <pair <unsigned int, int> > &projected) { if (minpat > pattern.size()) return; // print where & pattern if (where) { *os << "<pattern>" << endl; // what: if (all) { *os << "<freq>" << pattern[pattern.size()-1].second << "</freq>" << endl; *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first; } else { *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << "</what>" << endl; // where *os << "<where>"; for (unsigned int i = 0; i < projected.size(); i++) *os << (i ? " " : "") << projected[i].first; *os << "</where>" << endl; *os << "</pattern>" << endl; } else { // print found pattern only if (all) { *os << pattern[pattern.size()-1].second; for (unsigned int i = 0; i < pattern.size(); i++) *os << " " << pattern[i].first; } else { for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << endl; } } void project (vector <pair <unsigned int, int> > &projected) { if (all) report(projected); map <T, vector <pair <unsigned int, int> > > counter; for (unsigned int i = 0; i < projected.size(); i++) { int pos = projected[i].second; unsigned int id = projected[i].first; unsigned int size = transaction[id].size(); map <T, int> tmp; for (unsigned int j = pos + 1; j < size; j++) { T item = transaction[id][j]; if (tmp.find (item) == tmp.end()) tmp[item] = j ; } for (map <T, int>::iterator k = tmp.begin(); k != tmp.end(); ++k) counter[k->first].push_back (make_pair <unsigned int, int> (id, k->second)); } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end (); ) { if (l->second.size() < minsup) { map <T, vector <pair <unsigned int, int> > >::iterator tmp = l; tmp = l; ++tmp; counter.erase (l); l = tmp; } else { ++l; } } if (! all && counter.size () == 0) { report (projected); return; } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end(); ++l) { if (pattern.size () < maxpat) { pattern.push_back (make_pair <T, unsigned int> (l->first, l->second.size())); project (l->second); pattern.erase (pattern.end()); } } } public: PrefixSpan (unsigned int _minsup = 1, unsigned int _minpat = 1, unsigned int _maxpat = 0xffffffff, bool _all = false, bool _where = false, string _delimiter = "/", bool _verbose = false): minsup(_minsup), minpat (_minpat), maxpat (_maxpat), all(_all), where(_where), delimiter (_delimiter), verbose (_verbose) {}; ~PrefixSpan () {}; istream& read (istream &is) { string line; vector <T> tmp; T item; while (getline (is, line)) { tmp.clear (); istrstream istrs ((char *)line.c_str()); while (istrs >> item) tmp.push_back (item); transaction.push_back (tmp); } return is; } ostream& run (ostream &_os) { os = &_os; if (verbose) *os << transaction.size() << endl; vector <pair <unsigned int, int> > root; for (unsigned int i = 0; i < transaction.size(); i++) root.push_back (make_pair (i, -1)); project (root); return *os; } void clear () { transaction.clear (); pattern.clear (); } }; int main (int argc, char **argv) { extern char *optarg; unsigned int minsup = 1; unsigned int minpat = 1; unsigned int maxpat = 0xffffffff; bool all = false; bool where = false; string delimiter = "/"; bool verbose = false; string type = "string"; int opt; while ((opt = getopt(argc, argv, "awvt:M:m:L:d:")) != -1) { switch(opt) { case 'a': all = true; break; case 'w': where = true; break; case 'v': verbose = true; break; case 'm': minsup = atoi (optarg); break; case 'M': minpat = atoi (optarg); break; case 'L': maxpat = atoi (optarg); break; case 't': type = string (optarg); break; case 'd': delimiter = string (optarg); break; default: cout << "Usage: " << argv[0] << " [-m minsup] [-M minpat] [-L maxpat] [-a] [-w] [-v] [-t type] [-d delimiter] < data .." << endl; return -1; } } if (type == "int") { PrefixSpan<unsigned int> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); }else if (type == "short") { PrefixSpan<unsigned short> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "char") { PrefixSpan<unsigned char> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "string") { PrefixSpan<string> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else { cerr << "Unknown Item Type: " << type << " : choose from [string|int|short|char]" << endl; return -1; } return 0; }

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  • Azure &ndash; Part 5 &ndash; Repository Pattern for Table Service

    - by Shaun
    In my last post I created a very simple WCF service with the user registration functionality. I created an entity for the user data and a DataContext class which provides some methods for operating the entities such as add, delete, etc. And in the service method I utilized it to add a new entity into the table service. But I didn’t have any validation before registering which is not acceptable in a real project. So in this post I would firstly add some validation before perform the data creation code and show how to use the LINQ for the table service.   LINQ to Table Service Since the table service utilizes ADO.NET Data Service to expose the data and the managed library of ADO.NET Data Service supports LINQ we can use it to deal with the data of the table service. Let me explain with my current example: I would like to ensure that when register a new user the email address should be unique. So I need to check the account entities in the table service before add. If you remembered, in my last post I mentioned that there’s a method in the TableServiceContext class – CreateQuery, which will create a IQueryable instance from a given type of entity. So here I would create a method under my AccountDataContext class to return the IQueryable<Account> which named Load. 1: public class AccountDataContext : TableServiceContext 2: { 3: private CloudStorageAccount _storageAccount; 4:  5: public AccountDataContext(CloudStorageAccount storageAccount) 6: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 7: { 8: _storageAccount = storageAccount; 9:  10: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 11: _storageAccount.Credentials); 12: tableStorage.CreateTableIfNotExist("Account"); 13: } 14:  15: public void Add(Account accountToAdd) 16: { 17: AddObject("Account", accountToAdd); 18: SaveChanges(); 19: } 20:  21: public IQueryable<Account> Load() 22: { 23: return CreateQuery<Account>("Account"); 24: } 25: } The method returns the IQueryable<Account> so that I can perform the LINQ operation on it. And back to my service class, I will use it to implement my validation. 1: public bool Register(string email, string password) 2: { 3: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 4: var accountToAdd = new Account(email, password) { DateCreated = DateTime.Now }; 5: var accountContext = new AccountDataContext(storageAccount); 6:  7: // validation 8: var accountNumber = accountContext.Load() 9: .Where(a => a.Email == accountToAdd.Email) 10: .Count(); 11: if (accountNumber > 0) 12: { 13: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 14: } 15:  16: // create entity 17: try 18: { 19: accountContext.Add(accountToAdd); 20: return true; 21: } 22: catch (Exception ex) 23: { 24: Trace.TraceInformation(ex.ToString()); 25: } 26: return false; 27: } I used the Load method to retrieve the IQueryable<Account> and use Where method to find the accounts those email address are the same as the one is being registered. If it has I through an exception back to the client side. Let’s run it and test from my simple client application. Oops! Looks like we encountered an unexpected exception. It said the “Count” is not support by the ADO.NET Data Service LINQ managed library. That is because the table storage managed library (aka. TableServiceContext) is based on the ADO.NET Data Service and it supports very limit LINQ operation. Although I didn’t find a full list or documentation about which LINQ methods it supports I could even refer a page on msdn here. It gives us a roughly summary of which query operation the ADO.NET Data Service managed library supports and which doesn't. As you see the Count method is not in the supported list. Not only the query operation, there inner lambda expression in the Where method are limited when using the ADO.NET Data Service managed library as well. For example if you added (a => !a.DateDeleted.HasValue) in the Where method to exclude those deleted account it will raised an exception said "Invalid Input". Based on my experience you should always use the simple comparison (such as ==, >, <=, etc.) on the simple members (such as string, integer, etc.) and do not use any shortcut methods (such as string.Compare, string.IsNullOrEmpty etc.). 1: // validation 2: var accountNumber = accountContext.Load() 3: .Where(a => a.Email == accountToAdd.Email) 4: .ToList() 5: .Count; 6: if (accountNumber > 0) 7: { 8: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 9: } We changed the a bit and try again. Since I had created an account with my mail address so this time it gave me an exception said that the email had been used, which is correct.   Repository Pattern for Table Service The AccountDataContext takes the responsibility to save and load the account entity but only for that specific entity. Is that possible to have a dynamic or generic DataContext class which can operate any kinds of entity in my system? Of course yes. Although there's no typical database in table service we can threat the entities as the records, similar with the data entities if we used OR Mapping. As we can use some patterns for ORM architecture here we should be able to adopt the one of them - Repository Pattern in this example. We know that the base class - TableServiceContext provide 4 methods for operating the table entities which are CreateQuery, AddObject, UpdateObject and DeleteObject. And we can create a relationship between the enmity class, the table container name and entity set name. So it's really simple to have a generic base class for any kinds of entities. Let's rename the AccountDataContext to DynamicDataContext and make the type of Account as a type parameter if it. 1: public class DynamicDataContext<T> : TableServiceContext where T : TableServiceEntity 2: { 3: private CloudStorageAccount _storageAccount; 4: private string _entitySetName; 5:  6: public DynamicDataContext(CloudStorageAccount storageAccount) 7: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 8: { 9: _storageAccount = storageAccount; 10: _entitySetName = typeof(T).Name; 11:  12: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 13: _storageAccount.Credentials); 14: tableStorage.CreateTableIfNotExist(_entitySetName); 15: } 16:  17: public void Add(T entityToAdd) 18: { 19: AddObject(_entitySetName, entityToAdd); 20: SaveChanges(); 21: } 22:  23: public void Update(T entityToUpdate) 24: { 25: UpdateObject(entityToUpdate); 26: SaveChanges(); 27: } 28:  29: public void Delete(T entityToDelete) 30: { 31: DeleteObject(entityToDelete); 32: SaveChanges(); 33: } 34:  35: public IQueryable<T> Load() 36: { 37: return CreateQuery<T>(_entitySetName); 38: } 39: } I saved the name of the entity type when constructed for performance matter. The table name, entity set name would be the same as the name of the entity class. The Load method returned a generic IQueryable instance which supports the lazy load feature. Then in my service class I changed the AccountDataContext to DynamicDataContext and that's all. 1: var accountContext = new DynamicDataContext<Account>(storageAccount); Run it again and register another account. The DynamicDataContext now can be used for any entities. For example, I would like the account has a list of notes which contains 3 custom properties: Account Email, Title and Content. We create the note entity class. 1: public class Note : TableServiceEntity 2: { 3: public string AccountEmail { get; set; } 4: public string Title { get; set; } 5: public string Content { get; set; } 6: public DateTime DateCreated { get; set; } 7: public DateTime? DateDeleted { get; set; } 8:  9: public Note() 10: : base() 11: { 12: } 13:  14: public Note(string email) 15: : base(email, string.Format("{0}_{1}", email, Guid.NewGuid().ToString())) 16: { 17: AccountEmail = email; 18: } 19: } And no need to tweak the DynamicDataContext we can directly go to the service class to implement the logic. Notice here I utilized two DynamicDataContext instances with the different type parameters: Note and Account. 1: public class NoteService : INoteService 2: { 3: public void Create(string email, string title, string content) 4: { 5: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 6: var accountContext = new DynamicDataContext<Account>(storageAccount); 7: var noteContext = new DynamicDataContext<Note>(storageAccount); 8:  9: // validate - email must be existed 10: var accounts = accountContext.Load() 11: .Where(a => a.Email == email) 12: .ToList() 13: .Count; 14: if (accounts <= 0) 15: throw new ApplicationException(string.Format("The account {0} does not exsit in the system please register and try again.", email)); 16:  17: // save the note 18: var noteToAdd = new Note(email) { Title = title, Content = content, DateCreated = DateTime.Now }; 19: noteContext.Add(noteToAdd); 20: } 21: } And updated our client application to test the service. I didn't implement any list service to show all notes but we can have a look on the local SQL database if we ran it at local development fabric.   Summary In this post I explained a bit about the limited LINQ support for the table service. And then I demonstrated about how to use the repository pattern in the table service data access layer and make the DataContext dynamically. The DynamicDataContext I created in this post is just a prototype. In fact we should create the relevant interface to make it testable and for better structure we'd better separate the DataContext classes for each individual kind of entity. So it should have IDataContextBase<T>, DataContextBase<T> and for each entity we would have class AccountDataContext<Account> : IDataContextBase<Account>, DataContextBase<Account> { … } class NoteDataContext<Note> : IDataContextBase<Note>, DataContextBase<Note> { … }   Besides the structured data saving and loading, another common scenario would be saving and loading some binary data such as images, files. In my next post I will show how to use the Blob Service to store the bindery data - make the account be able to upload their logo in my example.   Hope this helps, Shaun   All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Why is this exception thrown when trying to match this regex in Java?

    - by Scott Ferguson
    I'm trying to match a specific string out of a an HTML document and have this regex pattern to grab it: Pattern somePattern = Pattern.compile("var json = ({\"r\":\"^d1\".*});"); However when I try to hit that code at runtime, I get this error: FATAL EXCEPTION: Timer-0 java.util.regex.PatternSyntaxException: Syntax error U_REGEX_RULE_SYNTAX near index 13: var json = ({"r":"^d1".*}); ^ at com.ibm.icu4jni.regex.NativeRegEx.open(Native Method) at java.util.regex.Pattern.compileImpl(Pattern.java:383) at java.util.regex.Pattern.<init>(Pattern.java:341) at java.util.regex.Pattern.compile(Pattern.java:317) Can anybody tell me what I'm doing wrong?

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  • Auto not being recognised by the compiler, what would be the best replacement?

    - by user1719605
    So I have wrote a program that uses auto however the compiler doesn't seem to recognize it, probably it is an earlier compiler. I was wondering for my code, with are suitable variables to fix my code so that I do not need to use the auto keyword? I'm thinking a pointer to a string? or a string iterator, though I am not sure. #include <cstdlib> #include <string> #include <iostream> #include <unistd.h> #include <algorithm> using namespace std; int main(int argc, char* argv[]) { enum MODE { WHOLE, PREFIX, SUFFIX, ANYWHERE, EMBEDDED } mode = WHOLE; bool reverse_match = false; int c; while ((c = getopt(argc, argv, ":wpsaev")) != -1) { switch (c) { case 'w': // pattern matches whole word mode = WHOLE; break; case 'p': // pattern matches prefix mode = PREFIX; break; case 'a': // pattern matches anywhere mode = ANYWHERE; break; case 's': // pattern matches suffix mode = SUFFIX; break; case 'e': // pattern matches anywhere mode = EMBEDDED; break; case 'v': // reverse sense of match reverse_match = true; break; } } argc -= optind; argv += optind; string pattern = argv[0]; string word; int matches = 0; while (cin >> word) { switch (mode) { case WHOLE: if (reverse_match) { if (pattern != word) { matches += 1; cout << word << endl; } } else if (pattern == word) { matches += 1; cout << word << endl; } break; case PREFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.begin(), pattern.end(), word.begin()); if (reverse_match) { if (res.first != word.end()) { matches += 1; cout << word << endl; } } else if (res.first == word.end()) { matches += 1; cout << word << endl; } } break; case ANYWHERE: if (reverse_match) { if (!word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } } else if (word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } break; case SUFFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.rbegin(), pattern.rend(), word.rbegin()); if (reverse_match) { if (res.first != word.rend()) { matches = +1; cout << word << endl; } } else if (res.first == word.rend()) { matches = +1; cout << word << endl; } } break; case EMBEDDED: if (reverse_match) { if (!pattern.find(word) != string::npos) { matches += 1; cout << word << endl;} } else if (pattern.find(word) != string::npos) { matches += 1; cout << word << endl; } break; } } return (matches == 0) ? 1 : 0; } Thanks in advance!

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  • Expert F# &ndash; Pattern Matching with Adam and Eve

    - by MarkPearl
    So I am loving my Expert F# book. I wish I had more time with it, but the little time I get I really enjoy. However today I was completely stumped by what the book was trying to get across with regards to pattern matching. On Page 38 – Chapter 3, it briefly describes F# option values. On this page it gives the code snippet along the code lines below and then goes on to speak briefly about pattern matching... open System type 'a option = | None | Some of 'a let people = [ ("Adam", None); ("Eve", None); ("Cain", Some("Adam", "Eve")); ("Abel", Some("Adam", "Eve")) ] let showParents(name, parents) = match parents with | Some(dad, mum) -> printfn "%s has father %s, mother %s" name dad mum | None -> printfn "%s has no parents!" name Console.WriteLine(showParents("Adam", None))   Originally when I read this code I think I misunderstood the purpose of the example code. I for some reason thought that the showParents function would magically be parsing the people array and looking for a match of name and then showing the parents. But obviously it cannot do this since there is no reference to the people array in the showParents method. After rereading the page I realized that I had just combined the two segments of code together, possibly incorrectly, and that a better example would have been to have a code snippet like the following. let showParents(name, parents) = match parents with | Some(dad, mum) -> printfn "%s has father %s, mother %s" name dad mum | None -> printfn "%s has no parents!" name Console.WriteLine(showParents("Adam", None)) Console.WriteLine(showParents("Cain", Some("Adam", "Eve"))) Console.ReadLine()   However, what if I wanted to have a function that was passed a list of people and a name would then show the parents of the name if there were any, and if not would show that they had no parents… so that doesnt seem to difficult does it… lets look at my very unoptimized noob F# code to try and achieve this… open System let people = [ ("Adam", None); ("Eve", None); ("Cain", Some("Adam", "Eve")); ("Abel", Some("Adam", "Eve")) ] // // returns the name of the person // let showName(person : string * (string * string) option) = let name = fst(person) name // // Returns a string with the parents details or not // let showParents(itemData : string * (string * string) option) = let name = fst(itemData) let parents = snd(itemData) match parents with | Some(dad, mum) -> "Father " + dad + " and Mother " + mum | None -> "Has no parents!" // // Prints the details // let showDetails(person : string * (string * string) option) = Console.WriteLine(showName(person)) Console.WriteLine(showParents(person)) // // Check if the name matches the first portion of person // if so, return true, else return false // let nameMatch(name : string , person : string * (string * string) option) = match name with | x when x = fst(person) -> true | _ -> false // // Searches an array of people and looks for a match of names // let findPerson(name : string, people : (string * (string * string) option) list) = let o = Seq.tryFind(fun x -> nameMatch(name, x)) people if Option.isSome o then o else Option.None // // Try and find a person, if found show their details // else show no match // let FoundPerson = findPerson("Cain", people) match FoundPerson with | None -> Console.WriteLine("Not found") | Some(x) -> showDetails(x) Console.ReadLine() So, my code isn’t the cleanest but it did teach me a bit more F#. The area that I learnt about was the option keyword. The challenge being, if a match of the name isn’t found – and if a name is found but the person doesn’t have parents it should react accordingly. I’m pretty sure I can optimize this code quite a bit more and I think I may come back to it sometime in the future and relook at it, but for now at least I was able to achieve what I wanted.. and my brain has gone just that wee little bit more functional.

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  • Nginx rewrites - When does one use the break flag (pattern target break)?

    - by anonymous-one
    The nginx wiki states: break - completes processing of current rewrite directives and non-rewrite processing continues within the current location block only. Is this to say that: If the rewrite pattern matches, process the rewrite (rewrite to target) but do not process any of the other rules in the location block, and process all other (cache, proxy, etc) directives in the location block? I am talking about the break flag as per: PATTERN TARGET FLAG Not the "break;" directive. Thanks.

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  • Ruby gem installation error after OSX Yosemite and Xcode 6 installation

    - by Andres Trevino
    I tried installing a gem like I did before installing Yosemite, but now I'm getting an error: /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:159:in `synchronize': ERROR: Failed to build gem native extension. (Gem::Ext::BuildError) ERROR: Failed to build gem native extension. deadlock; recursive locking This is the command I wrote: sudo gem install mysql2 This is the message it appears in the terminal: Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/autotest-fsevent-0.2.9 for inspection. Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-14/2.0.0/autotest-fsevent-0.2.9/gem_make.out Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/autotest-fsevent-0.2.9 for inspection. Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-14/2.0.0/autotest-fsevent-0.2.9/gem_make.out from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:159:in build_extension' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:198:inblock in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:195:in each' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:195:inbuild_extensions' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:1436:in block in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/user_interaction.rb:45:inuse_ui' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:1434:in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/stub_specification.rb:60:inbuild_extensions' from /Library/Ruby/Site/2.0.0/rubygems/basic_specification.rb:56:in contains_requirable_file?' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:925:inblock in find_inactive_by_path' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:in each' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:infind' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:in find_inactive_by_path' from /Library/Ruby/Site/2.0.0/rubygems.rb:185:intry_activate' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:132:in rescue in require' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:144:inrequire' from /Library/Ruby/Site/2.0.0/rubygems.rb:601:in load_yaml' from /Library/Ruby/Site/2.0.0/rubygems/config_file.rb:328:inload_file' from /Library/Ruby/Site/2.0.0/rubygems/config_file.rb:197:in initialize' from /Library/Ruby/Site/2.0.0/rubygems.rb:289:innew' from /Library/Ruby/Site/2.0.0/rubygems.rb:289:in configuration' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:63:inrun' from /Library/Ruby/Site/2.0.0/rubygems/ext/ext_conf_builder.rb:38:in block in build' from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/tempfile.rb:324:inopen' from /Library/Ruby/Site/2.0.0/rubygems/ext/ext_conf_builder.rb:17:in build' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:161:inblock (2 levels) in build_extension' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:160:in chdir' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:160:inblock in build_extension' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:159:in synchronize' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:159:inbuild_extension' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:198:in block in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:195:ineach' from /Library/Ruby/Site/2.0.0/rubygems/ext/builder.rb:195:in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:1436:inblock in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/user_interaction.rb:45:in use_ui' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:1434:inbuild_extensions' from /Library/Ruby/Site/2.0.0/rubygems/stub_specification.rb:60:in build_extensions' from /Library/Ruby/Site/2.0.0/rubygems/basic_specification.rb:56:incontains_requirable_file?' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:925:in block in find_inactive_by_path' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:ineach' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:in find' from /Library/Ruby/Site/2.0.0/rubygems/specification.rb:924:infind_inactive_by_path' from /Library/Ruby/Site/2.0.0/rubygems.rb:185:in try_activate' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:132:inrescue in require' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:144:in require' from /Library/Ruby/Site/2.0.0/rubygems.rb:601:inload_yaml' from /Library/Ruby/Site/2.0.0/rubygems/config_file.rb:328:in load_file' from /Library/Ruby/Site/2.0.0/rubygems/config_file.rb:197:ininitialize' from /Library/Ruby/Site/2.0.0/rubygems/gem_runner.rb:74:in new' from /Library/Ruby/Site/2.0.0/rubygems/gem_runner.rb:74:indo_configuration' from /Library/Ruby/Site/2.0.0/rubygems/gem_runner.rb:39:in run' from /usr/bin/gem:21:in' I am using OSX 10.10 and Xcode 6 Beta. Do any of you guys have any idea as to what to do about this? Thanks in advance

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  • Essential AIML responses?

    - by user335932
    What do you think are important pattern/temples to program. Like in a chatbot what does EVERY chatbot need a response for? Im just starting out making the aiml file and need some help... Heres the file now. <aiml> <category> <pattern>Hey</pattern> <template>Whats up?</template> <category> <category> <pattern>WHAT ARE YOU?</pattern> <template>I am a chatbot.</template> <category> <category> <pattern>DO YOU LIKE*</pattern> <template>Yes, I love <star/></template> <category> <category> <pattern>WHAT IS*</pattern> <template><star/>? is that what humans call what I did to your mom last night?</template> <category> <category> <pattern>WHEN WERE YOUR BORN*</pattern> <template>I was created in 2010.</template> <category>

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  • I need to remove Java Script tags using regular expressions and JRegex

    - by piotr
    I need to remove all the Java Script tags and the content in between and style tags from the HTML code of web pages.So far I've come up with this expression : "(<[ \r\n\t]script([ \r\n\t]|){1,}([ \r\n\t]|.)?)|(<[ \r\n\t]noscript([ \r\n\t]|){1,}([ \r\n\t]|.)?)|(<[ \r\n\t]style([ \r\n\t]|){1,}([ \r\n\t]|.)?)" I use JRegex library to work with regular expressions. When I test it in any regex tester it works just fine, but once I run my program - it all crashes down with this error report: Exception in thread "Thread-0" java.lang.StackOverflowError at java.util.regex.Pattern$BranchConn.match(Unknown Source) at java.util.regex.Pattern$BmpCharProperty.match(Unknown Source) at java.util.regex.Pattern$Branch.match(Unknown Source) at java.util.regex.Pattern$GroupHead.match(Unknown Source) at java.util.regex.Pattern$LazyLoop.match(Unknown Source) at java.util.regex.Pattern$GroupTail.match(Unknown Source) at java.util.regex.Pattern$BranchConn.match(Unknown Source) at java.util.regex.Pattern$CharProperty.match(Unknown Source) at java.util.regex.Pattern$Branch.match(Unknown Source) at java.util.regex.Pattern$GroupHead.match(Unknown Source) at java.util.regex.Pattern$LazyLoop.match(Unknown Source) .................................. And it keeps on going forever. If anyone can give me an advice on this one - I'll be very grateful.

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  • C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

    - by James Michael Hare
    So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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  • Can I do filename pattern matching in a bash script?

    - by Bob Bowden
    Can I do filename pattern matching in a bash script? "test" is a directory with the following files ... bob@bob-laptop:~/test$ ls exclude exclude1 exclude2 include1 include2 from the command line, if I want to exclude some of the files, I can do ... bob@bob-laptop:~/test$ echo !(exclude*) include1 include2 but, if I put that command in a script (named exclude) ... bob@bob-laptop:~/test$ cat exclude echo !(exclude*) when I execute it, I get an error ... bob@bob-laptop:~/test$ ./exclude ./exclude: line 1: syntax error near unexpected token (' ./exclude: line 1:echo !(exclude*)' I've tried every (I think) variation of escaping some, all or none of the special characters and I still get an error. What am I missing here? If I can't do this, would someone please be so kind as to explain why?

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  • ubuntu 11.10 foreman error

    - by user1060759
    Like this post I am also trying to complete this heroku tutorial I have installed and used everything (node.js, npm, express) successfully until I got to Foreman. I installed Foreman by first installing Ruby: alex@ubuntu:~$ sudo apt-get install ruby1.9.1 then installing Foreman. I am a newbie to Unix so I "sudo" perhaps unnecessarily here, but I got confirmation in the terminal that it had installed but also some errors: alex@ubuntu:~/NodeHelloWorld$ sudo gem install foreman Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" Successfully installed term-ansicolor-1.0.7 Successfully installed foreman-0.26.1 Then when I try to start foreman I get similar: alex@ubuntu:~/NodeHelloWorld$ foreman start Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:926:in `report_activate_error': Could not find RubyGem foreman (>= 0) (Gem::LoadError) from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:244:in `activate_dep' from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:236:in `activate' from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:1307:in `gem' from /usr/local/bin/foreman:18 Can anyone help me? I am a newbie to Unix after finally dumping windows as I found I could not get foreman-windows to work for me either I have found this post from someone with apparently the same issue. Does this mean my version of ruby could be wrong? I am running 1.9.1, though again new to ruby as well; alex@ubuntu:~/NodeHelloWorld$ ruby1.9.1 -v ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux] Thanks

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  • When modeling a virtual circuit board, what is the best design pattern to check for cycles?

    - by Wallace Brown
    To make it simple assume you have only AND and OR gates. Each has two inputs and one output. The output of two inputs can be used as an input for the next gate For example: A AND B - E C AND D - F E OR F - G Assuming an arbitrary number of gates, we want to check if the circuit ever connects back into itself at an earlier state? For example: E AND F - A This should be illegal since it creates an endless cycle. What design pattern would best be able to check for these cycles?

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  • Is is common to use the command pattern for property get/sets?

    - by k rey
    Suppose I have a controller class with a bunch of properties. Each time a property is changed, I would like to update the model. Now also suppose that I use the command pattern to perform model updates. Is it common to use command classes within property get and sets of the controller class or is there a better way? Here is an example of what I am currently using: class MyController { private int _myInt; public int MyInt { get { return _myInt; } set { MyCommand cmd = new MyCommand(); cmd.Argument = _myInt; cmd.Execute(); // Command object updates the model } } }

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  • Is loose coupling w/o use cases an anti-pattern?

    - by dsimcha
    Loose coupling is, to some developers, the holy grail of well-engineered software. It's certainly a good thing when it makes code more flexible in the face of changes that are likely to occur in the foreseeable future, or avoids code duplication. On the other hand, efforts to loosely couple components increase the amount of indirection in a program, thus increasing its complexity, often making it more difficult to understand and often making it less efficient. Do you consider a focus on loose coupling without any use cases for the loose coupling (such as avoiding code duplication or planning for changes that are likely to occur in the foreseeable future) to be an anti-pattern? Can loose coupling fall under the umbrella of YAGNI?

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  • would a composite design pattern be useful for group membership?

    - by changokun
    I'm trying to think about the best way to handle group memberships on a website. People sign up and select checkboxes in a list of interests. Every week we send out interest-themed emails to those members that indicated that interest. however i store the information in the database, while i am working with the lists and generating lists of email addresses or manipulating group memberships, the composite design pattern looked interesting. it would be easy to populate the group, then do some aggregating functions that say... generate the list of email addresses based on the interests. but i'm not sure i'm seeing any other advantages. i do need something scalable, and flexible. thoughts?

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  • What design pattern do you use to support graceful fallback on old platforms?

    - by JoJo
    Let's say I need to add a drop shadow behind a box. Some old platforms do not support drop shadows, so I have to fake it by putting an image behind the box. Here's the pseudo code of how I'm currently handling this fallback: if (dropShadowsAreSupported) { box.addDropShadow("black"); } else { box.putImageBehindIt("gaussianBlur.png"); } Is this the right way to handle it? It seems too amateur to me. Is there a better design pattern?

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