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• My architecture has a problem with views that required information from different objects. How can I solve this?

  - by Oscar

  I am building an architecture like this: These are my SW layers ______________ | | | Views | |______________| ______________ | | |Business Logic| |______________| ______________ | | | Repository | |______________| My views are going to generate my HTML to be sent to the user Business logic is where all the business logics are Repository is a layer to access the DB My idea is that the repository uses entities (that are basically the representation of the tables, in order to perform DB queries. The layers communicate between themselves using Business Objects, that are objects that represent the real-world-object itself. They can contain business rules and methods. The views build/use DTOs, they are basically objects that have the information required to be shown on the screen. They expect also this kind of object on actions and, before calling the business logic, they create BO. First question: what is your overall feeling about this architecture? I've used similar architecture for some projects and I always got this problem: If my view has this list to show : Student1, age, course, Date Enrolled, Already paid? It has information from different BO. How do you think one should build the structure? These were the alternatives I could think of: The view layer could call the methods to get the student, then the course it studies, then the payment information. This would cause a lot of DB accesses and my view would have the knowledge about how to act to generate this information. This just seems wrong for me. I could have an "adapter object", that has the required information (a class that would have a properties Student, Course and Payment). But I would required one adapter object for each similar case, this may get very bad for big projects. I still don't like them. Would you have ideas? How would you change the architecture to avoid this kind of problems? @Rory: I read the CQRS and I don't think this suits my needs. As taken from a link references in your link Before describing the details of CQRS we need to understand the two main driving forces behind it: collaboration and staleness That means: many different actors using the same object (collaboration) and once data has been shown to a user, that same data may have been changed by another actor – it is stale (staleness). My problem is that I want to show to the user information from different BO, so I would need to receive them from the service layer. How can my service layer assemble and deliver this information? Edit to @AndrewM: Yes, you understood it correctly, the original idea was to have the view layer to build the BOs, but you have a very nice point about the creation of the BO inside the business layers. Assuming I follow your advice and move the creation logic inside the business layer, my business layer interface would contain the DTOs, for instance public void foo(MyDTO object) But as far as I understand, the DTO is tightly coupled to each view, so it would not be reusable by a second view. In order to use it, the second view would need to build a specific DTO from a specific view or I would have to duplicate the code in the business layer. Is this correct or am I missing something?

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• Use a custom value object or a Guid as an entity identifier in a distributed system?

  - by Kazark

  tl;dr I've been told that in domain-driven design, an identifier for an entity could be a custom value object, i.e. something other than Guid, string, int, etc. Can this really be advisable in a distributed system? Long version I will invent an situation analogous to the one I am currently facing. Say I have a distributed system in which a central concept is an egg. The system allows you to order eggs and see spending reports and inventory-centric data such as quantity on hand, usage, valuation and what have you. There area variety of services backing these behaviors. And say there is also another app which allows you to compose recipes that link to a particular egg type. Now egg type is broken down by the species—ostrich, goose, duck, chicken, quail. This is fine and dandy because it means that users don't end up with ostrich eggs when they wanted quail eggs and whatnot. However, we've been getting complaints because jumbo chicken eggs are not even close to equivalent to small ones. The price is different, and they really aren't substitutable in recipes. And here we thought we were doing users a favor by not overwhelming them with too many options. Currently each of the services (say, OrderSubmitter, EggTypeDefiner, SpendingReportsGenerator, InventoryTracker, RecipeCreator, RecipeTracker, or whatever) are identifying egg types with an industry-standard integer representation the species (let's call it speciesCode). We realize we've goofed up because this change could effect every service. There are two basic proposed solutions: Use a predefined identifier type like Guid as the eggTypeID throughout all the services, but make EggTypeDefiner the only service that knows that this maps to a speciesCode and eggSizeCode (and potentially to an isOrganic flag in the future, or whatever). Use an EggTypeID value object which is a combination of speciesCode and eggSizeCode in every service. I've proposed the first solution because I'm hoping it better encapsulates the definition of what an egg type is in the EggTypeDefiner and will be more resilient to changes, say if some people now want to differentiate eggs by whether or not they are "organic". The second solution is being suggested by some people who understand DDD better than I do in the hopes that less enrichment and lookup will be necessary that way, with the justification that in DDD using a value object as an ID is fine. Also, they are saying that EggTypeDefiner is not a domain and EggType is not an entity and as such should not have a Guid for an ID. However, I'm not sure the second solution is viable. This "value object" is going to have to be serialized into JSON and URLs for GET requests and used with a variety of technologies (C#, JavaScript...) which breaks encapsulation and thus removes any behavior of the identifier value object (is either of the fields optional? etc.) Is this a case where we want to avoid something that would normally be fine in DDD because we are trying to do DDD in a distributed fashion? Summary Can it be a good idea to use a custom value object as an identifier in a distributed system (solution #2)?

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• Serializing object with no namespaces using DataContractSerializer

  - by Yurik

  How do I remove XML namespaces from an object's XML representation serialized using DataContractSerializer? That object needs to be serialized to a very simple output XML. Latest & greatest - using .Net 4 beta 2 The object will never need to be deserialized. XML should not have any xmlns:... namespace refs Any subtypes of Exception and ISubObject need to be supported. It will be very difficult to change the original object. Object: [Serializable] class MyObj { string str; Exception ex; ISubObject subobj; } Need to serialize into: <xml> <str>...</str> <ex i:nil="true" /> <subobj i:type="Abc"> <AbcProp1>...</AbcProp1> <AbcProp2>...</AbcProp2> </subobj> </xml> I used this code: private static string ObjectToXmlString(object obj) { if (obj == null) throw new ArgumentNullException("obj"); var serializer = new DataContractSerializer( obj.GetType(), null, Int32.MaxValue, false, false, null, new AllowAllContractResolver()); var sb = new StringBuilder(); using (var xw = XmlWriter.Create(sb, new XmlWriterSettings { OmitXmlDeclaration = true, NamespaceHandling = NamespaceHandling.OmitDuplicates, Indent = true })) { serializer.WriteObject(xw, obj); xw.Flush(); return sb.ToString(); } } From this article I adopted a DataContractResolver so that no subtypes have to be declared: public class AllowAllContractResolver : DataContractResolver { public override bool TryResolveType(Type dataContractType, Type declaredType, DataContractResolver knownTypeResolver, out XmlDictionaryString typeName, out XmlDictionaryString typeNamespace) { if (!knownTypeResolver.TryResolveType(dataContractType, declaredType, null, out typeName, out typeNamespace)) { var dictionary = new XmlDictionary(); typeName = dictionary.Add(dataContractType.FullName); typeNamespace = dictionary.Add(dataContractType.Assembly.FullName); } return true; } public override Type ResolveName(string typeName, string typeNamespace, Type declaredType, DataContractResolver knownTypeResolver) { return knownTypeResolver.ResolveName(typeName, typeNamespace, declaredType, null) ?? Type.GetType(typeName + ", " + typeNamespace); } }

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• Hopcroft–Karp algorithm in Python

  - by Simon

  I am trying to implement the Hopcroft Karp algorithm in Python using networkx as graph representation. Currently I am as far as this: #Algorithms for bipartite graphs import networkx as nx import collections class HopcroftKarp(object): INFINITY = -1 def __init__(self, G): self.G = G def match(self): self.N1, self.N2 = self.partition() self.pair = {} self.dist = {} self.q = collections.deque() #init for v in self.G: self.pair[v] = None self.dist[v] = HopcroftKarp.INFINITY matching = 0 while self.bfs(): for v in self.N1: if self.pair[v] and self.dfs(v): matching = matching + 1 return matching def dfs(self, v): if v != None: for u in self.G.neighbors_iter(v): if self.dist[ self.pair[u] ] == self.dist[v] + 1 and self.dfs(self.pair[u]): self.pair[u] = v self.pair[v] = u return True self.dist[v] = HopcroftKarp.INFINITY return False return True def bfs(self): for v in self.N1: if self.pair[v] == None: self.dist[v] = 0 self.q.append(v) else: self.dist[v] = HopcroftKarp.INFINITY self.dist[None] = HopcroftKarp.INFINITY while len(self.q) > 0: v = self.q.pop() if v != None: for u in self.G.neighbors_iter(v): if self.dist[ self.pair[u] ] == HopcroftKarp.INFINITY: self.dist[ self.pair[u] ] = self.dist[v] + 1 self.q.append(self.pair[u]) return self.dist[None] != HopcroftKarp.INFINITY def partition(self): return nx.bipartite_sets(self.G) The algorithm is taken from http://en.wikipedia.org/wiki/Hopcroft%E2%80%93Karp_algorithm However it does not work. I use the following test code G = nx.Graph([ (1,"a"), (1,"c"), (2,"a"), (2,"b"), (3,"a"), (3,"c"), (4,"d"), (4,"e"),(4,"f"),(4,"g"), (5,"b"), (5,"c"), (6,"c"), (6,"d") ]) matching = HopcroftKarp(G).match() print matching Unfortunately this does not work, I end up in an endless loop :(. Can someone spot the error, I am out of ideas and I must admit that I have not yet fully understand the algorithm, so it is mostly an implementation of the pseudo code on wikipedia

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• Cocoa equivalent of the Carbon method getPtrSize

  - by Michael Minerva

  I need to translate the a carbon method into cocoa into and I am having trouble finding any documentation about what the carbon method getPtrSize really does. From the code I am translating it seems that it returns the byte representation of an image but that doesn't really match up with the name. Could someone give me a good explanation of this method or link me to some documentation that describes it. The code I am translating is in a common lisp implementation called MCL that has a bridge to carbon (I am translating into CCL which is a common lisp implementation with a Cocoa bridge). Here is the MCL code (#_before a method call means that it is a carbon method): (defmethod COPY-CONTENT-INTO ((Source inflatable-icon) (Destination inflatable-icon)) ;; check for size compatibility to avoid disaster (unless (and (= (rows Source) (rows Destination)) (= (columns Source) (columns Destination)) (= (#_getPtrSize (image Source)) (#_getPtrSize (image Destination)))) (error "cannot copy content of source into destination inflatable icon: incompatible sizes")) ;; given that they are the same size only copy content (setf (is-upright Destination) (is-upright Source)) (setf (height Destination) (height Source)) (setf (dz Destination) (dz Source)) (setf (surfaces Destination) (surfaces Source)) (setf (distance Destination) (distance Source)) ;; arrays (noise-map Source) ;; accessor makes array if needed (noise-map Destination) ;; ;; accessor makes array if needed (dotimes (Row (rows Source)) (dotimes (Column (columns Source)) (setf (aref (noise-map Destination) Row Column) (aref (noise-map Source) Row Column)) (setf (aref (altitudes Destination) Row Column) (aref (altitudes Source) Row Column)))) (setf (connectors Destination) (mapcar #'copy-instance (connectors Source))) (setf (visible-alpha-threshold Destination) (visible-alpha-threshold Source)) ;; copy Image: slow byte copy (dotimes (I (#_getPtrSize (image Source))) (%put-byte (image Destination) (%get-byte (image Source) i) i)) ;; flat texture optimization: do not copy texture-id -> destination should get its own texture id from OpenGL (setf (is-flat Destination) (is-flat Source)) ;; do not compile flat textures: the display list overhead slows things down by about 2x (setf (auto-compile Destination) (not (is-flat Source))) ;; to make change visible we have to reset the compiled flag (setf (is-compiled Destination) nil))

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• How can I internationalize strings representing C# enum values?

  - by Duke

  I've seen many questions and answers about mapping strings to enums and vice-versa, but how can I map a series of localized strings to enums? Should I just create an extension method like this that returns the proper string from a resource file? Is there a way to localize attributes (like "Description") that are used in solutions like this? Which is the preferred solution - extension method or attributes. It seems to me that this isn't the intended purpose of attributes. In fact, now that I think about it, if I were to use an extension method an attribute seems like something I'd use to specify a key in a resource file for the localized string I want to use in place of the enum value. EDIT - example: Given the following enum, public enum TransactionTypes { Cheque = 1, BankTransfer = 2, CreditCard = 3 } I would like a way to map each type to a localized string. I started off with an extension method for the enum that uses a switch statement and strongly typed references to the resource file. However, an extension method for every enum doesn't seem like a great solution. I've started following this to create a custom attribute for each enumerated value. The attribute has a base name and key for the resource file containing localized strings. In the above enum, for example, I have this: ... [EnumResourceAttribute("FinancialTransaction", "Cheque")] Cheque = 1, ... Where "FinanacialTransaction" is the resx file and "Cheque" is the string key. I'm trying to create a utility method to which I could pass any value from any enumeration and have it return the localized string representation of that value, assuming the custom attribute is specified. I just can't figure out how to dynamically access a resource file and a key within it.

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• How to program a neural network for chess?

  - by marco92w

  Hello! I want to program a chess engine which learns to make good moves and win against other players. I've already coded a representation of the chess board and a function which outputs all possible moves. So I only need an evaluation function which says how good a given situation of the board is. Therefore, I would like to use an artificial neural network which should then evaluate a given position. The output should be a numerical value. The higher the value is, the better is the position for the white player. My approach is to build a network of 385 neurons: There are six unique chess pieces and 64 fields on the board. So for every field we take 6 neurons (1 for every piece). If there is a white piece, the input value is 1. If there is a black piece, the value is -1. And if there is no piece of that sort on that field, the value is 0. In addition to that there should be 1 neuron for the player to move. If it is White's turn, the input value is 1 and if it's Black's turn, the value is -1. I think that configuration of the neural network is quite good. But the main part is missing: How can I implement this neural network into a coding language (e.g. Delphi)? I think the weights for each neuron should be the same in the beginning. Depending on the result of a match, the weights should then be adjusted. But how? I think I should let 2 computer players (both using my engine) play against each other. If White wins, Black gets the feedback that its weights aren't good. So it would be great if you could help me implementing the neural network into a coding language (best would be Delphi, otherwise pseudo-code). Thanks in advance!

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• Swig typecast to derived class?

  - by Zack

  I notice that Swig provides a whole host of functions to allow for typecasting objects to their parent classes. However, in C++ one can produce a function like the following: A * getAnObject() { if(someBoolean) return (A *) new B; else return (A *) new C; } Where "A" is the parent of classes "B" and "C". One can then typecast the pointer returned into being a "B" type or "C" type at one's convenience like: B * some_var = (B *) getAnObject(); Is there some way I can typecast an object I've received from a generic-pointer-producing function at run-time in the scripting language using the wrappers? (In my case, Lua?) I have a function that could produce one of about a hundred possible classes, and I'd like to avoid writing an enormous switch structure that I'd have to maintain in C++. At the point where I receive the generic pointer, I also have a string representation of the data type I'd like to cast it to. Any thoughts? Thanks! -- EDIT -- I notice that SWIG offers to generate copy constructors for all of my classes. If I had it generate those, could I do something like the following?: var = myModule.getAnObject(); -- Function that returns an object type-cast down to a pointer of the parent class, as in the function getAnObject() above. var = myModule.ClassThatExtendsBaseClass(var); -- A copy constructor that SWIG theoretically creates for me and have var then be an instance of the inheriting class that knows it's an instance of the inheriting class?

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• How do I copy a python function to a remote machine and then execute it?

  - by Hugh

  I'm trying to create a construct in Python 3 that will allow me to easily execute a function on a remote machine. Assuming I've already got a python tcp server that will run the functions it receives, running on the remote server, I'm currently looking at using a decorator like @execute_on(address, port) This would create the necessary context required to execute the function it is decorating and then send the function and context to the tcp server on the remote machine, which then executes it. Firstly, is this somewhat sane? And if not could you recommend a better approach? I've done some googling but haven't found anything that meets these needs. I've got a quick and dirty implementation for the tcp server and client so fairly sure that'll work. I can get a string representation the function (e.g. func) being passed to the decorator by import inspect string = inspect.getsource(func) which can then be sent to the server where it can be executed. The problem is, how do I get all of the context information that the function requires to execute? For example, if func is defined as follows, import MyModule def func(): result = MyModule.my_func() MyModule will need to be available to func either in the global context or funcs local context on the remote server. In this case that's relatively trivial but it can get so much more complicated depending on when and how import statements are used. Is there an easy and elegant way to do this in Python? The best I've come up with at the moment is using the ast library to pull out all import statements, using the inspect module to get string representations of those modules and then reconstructing the entire context on the remote server. Not particularly elegant and I can see lots of room for error. Thanks for your time

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• Linux Device Driver - what's wrong with my device_read()?

  - by Rob

  My device /dev/my_inc is meant to take a positive integer N represented as an ascii string, and store it. Any read from /dev/my_inc will produce the ascii string representation of N + 1. The problem is that when I cat /dev/my_inc, I only get the first byte of myinc_value output to my shell, even though I have bytes_read == 2 at the end of my loop. /* Read from the device *********************/ static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t *offset) { char c; int bytes_read = 0; int value = myinc_value + 1; printk(KERN_INFO "my_inc device_read() called with value %d and msg %s.\n", value, msg); /* No bytes read if pointer to 0 */ if (*msg_ptr == 0) return 0; /* Put the incremented value in msg */ snprintf(msg, MAX_LENGTH, "%d", value); /* Put bytes from msg into user space buffer */ while (length && *msg_ptr) { c = *(msg_ptr++); printk(KERN_INFO "%s device_read() read %c.", DEV_NAME, c); if(put_user(c, buffer++)) return -EFAULT; length--; bytes_read++; } printk("my_inc device_read() returning %d.\n", bytes_read); /* Return bytes copied */ return bytes_read; }

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• Text mining on large database (data mining)

  - by yox

  Hello, I have a large database of resumes (CV), and a certain table skills grouping all users skills. inside that table there's a field skill_text that describes the skill in full text. I'm looking for an algorithm/software/method to extract significant terms/phrases from that table in order to build a new table with standarized skills.. Here are some examples skills extracted from the DB : Sectoral and competitive analysis Business Development (incl. in international settings) Specific structure and road design software - Microstation, Macao, AutoCAD (basic knowledge) Creative work (Photoshop, In-Design, Illustrator) checking and reporting back on campaign progress organising and attending events and exhibitions Development : Aptana Studio, PHP, HTML, CSS, JavaScript, SQL, AJAX Discipline: One to one marketing, E-marketing (SEO & SEA, display, emailing, affiliate program) Mix marketing, Viral Marketing, Social network marketing. The output shoud be something like : Sectoral and competitive analysis Business Development Specific structure and road design software - Macao AutoCAD Photoshop In-Design Illustrator organising events Development Aptana Studio PHP HTML CSS JavaScript SQL AJAX Mix marketing Viral Marketing Social network marketing emailing SEO One to one marketing As you see only skills remains no other representation text. I know this is possible using text mining technics but how to do it ? the database is realy large.. it's a good thing because we can calculate text frequency and decide if it's a real skill or just meaningless text... The big problem is .. how to determin that "blablabla" is a skill ? thanks

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• Scheme Depth-first search of a graph function

  - by John Retallack

  This is a homework question,I'm trying to do a Depth-first search function in Scheme,Here's the code I've written so far: (define explore (?(node visited) (let* ([neighbors (force (cdr node))] [next (nextNode visited neighbors)] [is-visited (member? node visited)]) (cond ;if I have no unvisited neighbours print current node and go up one level [(equal? next #f) (begin (display (car node)) (display " "))] ;if current node is not visited and I have unvisited neighbors ;print current node,mark as visited and visit it's neighbors [(and (equal? is-visited #f) (not (equal? next #f))) (begin (display (car node)) (display " ") (explore next (cons node visited)))]) ;go and visit the next neighbor (if (not (equal? (nextNode (cons next visited) neighbors) #f )) (explore (nextNode (cons next visited) neighbors) (cons node visited)))))) 'node' is the current node 'visited' is a list in witch I keep track of the nodes I visited 'nextNode' is a function that returns the first unvisited neighbor if any or #f otherwise 'member?' test's if a node is in the visited list The Graph representation is using adjacent made using references to nodes with letrec so that's why I use force in 'neighbors': Eg: (letrec ([node1 (list "NY" (delay (list node2 node3)))],where node2 and node3 are defined as node1 The problem witch I'm dealing with is that my visited lists looses track of some of the nodes I visited when I come out of recursion,How can I fix this ?

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• Shift-reduce: when to stop reducing?

  - by Joey Adams

  I'm trying to learn about shift-reduce parsing. Suppose we have the following grammar, using recursive rules that enforce order of operations, inspired by the ANSI C Yacc grammar: S: A; P : NUMBER | '(' S ')' ; M : P | M '*' P | M '/' P ; A : M | A '+' M | A '-' M ; And we want to parse 1+2 using shift-reduce parsing. First, the 1 is shifted as a NUMBER. My question is, is it then reduced to P, then M, then A, then finally S? How does it know where to stop? Suppose it does reduce all the way to S, then shifts '+'. We'd now have a stack containing: S '+' If we shift '2', the reductions might be: S '+' NUMBER S '+' P S '+' M S '+' A S '+' S Now, on either side of the last line, S could be P, M, A, or NUMBER, and it would still be valid in the sense that any combination would be a correct representation of the text. How does the parser "know" to make it A '+' M So that it can reduce the whole expression to A, then S? In other words, how does it know to stop reducing before shifting the next token? Is this a key difficulty in LR parser generation?

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• Why are floating point values so prolific?

  - by Kibbee

  So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster with floating point numbers, however, I can think of only a few cases that they actually the right data type would be using. If you sat back and think about every time you used a floating point value, how many times did you say, well, some error would be ok, as long as the result was a few microseconds faster. It really makes me think because Jeff was talking about NP completeness, and how heuristics give an answer that is kind of right. And well, computers shouldn't do that. They should give you the answer that is correct. Yet we see floating point values used in many applications where they are completely not valid. What really bugs me, isn't that floating point exists, but that in many languages, there isn't even a viable alternative, non-floating point, decimal value. A lot of programmers when doing financial applications have to fall back to storing the number of cents in an integer field. Which brings with it all kinds of other problems. Why do floats continue to be so prolific, even though they can't represent the real answer, and we expect computers to be accurate? [EDIT] Just to clarify, I was talking about Base 2 floating points, and not base 10 floating points. .Net offers the Decimal data type, which is a base 10 floating point value which offers a much better representation of the numbers we deal with on a daily basis in most computer programs. I find it hard to believe that even modern languages like Java don't support base 10 floating point values, unless you want to move into the realm of things like BigDecimal, which isn't really the right answer either in a lot of situations.

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• Java complex validation in Dropwizard?

  - by miku

  I'd like to accept JSON on an REST endpoint and convert it to the correct type for immediate validation. The endpoint looks like this: @POST public Response createCar(@Valid Car car) { // persist to DB // ... } But there are many subclasses of Car, e.g. Van, SelfDrivingCar, RaceCar, etc. How could I accept the different JSON representations on the endpoint, while keeping the validation code in the Resource as concise as something like @Valid Car car? Again: I send in JSON like (here, it's the representation of a subclass of Car, namely SelfDrivingCar): { "id" : "t1", // every Car has an Id "kind" : "selfdriving", // every Car has a type-hint "max_speed" : "200 mph", // some attribute "ai_provider" : "fastcarsai ltd." // this is SelfDrivingCar-specific } and I'd like the validation machinery look into the kind attribute, create an instance of the appropriate subclass, here e.g. SelfDrivingCar and perform validation. I know I could create different endpoints for all kind of cars, but thats does not seem DRY. And I know that I could use a real Validator instead of the annotation and do it by hand, so I'm just asking if there's some elegant shortcut for this problem.

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• Why does division yield a vastly different result than multiplication by a fraction in floating points.

  - by Avram

  I understand why floating point numbers can't be compared, and know about the mantissa and exponent binary representation, but I'm no expert and today I came across something I don't get: Namely lets say you have something like: float denominator, numerator, resultone, resulttwo; resultone = numerator / denominator; float buff = 1 / denominator; resulttwo = numerator * buff; To my knowledge different flops can yield different results and this is not unusual. But in some edge cases these two results seem to be vastly different. To be more specific in my GLSL code calculating the Beckmann facet slope distribution for the Cook-Torrance lighitng model: float a = 1 / (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); float b = clampedCosHalfNormal * clampedCosHalfNormal - 1.0; float c = facetSlopeRMS * facetSlopeRMS * clampedCosHalfNormal * clampedCosHalfNormal; facetSlopeDistribution = a * exp(b/c); yields very very different results to float a = (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); facetDlopeDistribution = exp(b/c) / a; Why does it? The second form of the expression is problematic. If I say try to add the second form of the expression to a color I get blacks, even though the expression should always evaluate to a positive number. Am I getting an infinity? A NaN? if so why?

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• finding "line-breaks" in textarea that is word-wrapping ARABIC text

  - by Irfan jamal

  I have a string of text that I display in a textarea (right-to-left orientation). The user can resize the textarea dynamically (I use jquery for this) and the text will wrap as necessary. When the user hits submit, I will take that text and create an image using PHP, BUT before submitting I would like to know where the "line-breaks" or rather "word-wraps" occur. Everywhere I have looked so far only shows me how to process line-breaks on the php side. I want to make it clear that there ARE NO LINE-BREAKS. What I have is one LONG string that will be word-wrapped in different ways based on the width of the textarea set by the user. I can't use "columns" or any other standard width representation because I have a very complex arabic font that is actually composed of glyphs (characters) of numerous different widths. If anyone knows of a way of accessing where the word wraps occur (either in a textarea or a div if need-be), I'd really like to know. My only other solution is to actually store (in my DB) the width of every single character (somewhat tedious since there are over 200 characters in 600 different fonts, for a total of...some huge number). My hopes aren't high, but I thought I would ask. Thanks i. jamal

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• Trying to parse OpenCV YAML ouput with yaml-cpp

  - by Kenn Sebesta

  I've got a series of OpenCv generated YAML files and would like to parse them with yaml-cpp I'm doing okay on simple stuff, but the matrix representation is proving difficult. # Center of table tableCenter: !!opencv-matrix rows: 1 cols: 2 dt: f data: [ 240, 240] This should map into the vector 240 240 with type float. My code looks like: #include "yaml.h" #include <fstream> #include <string> struct Matrix { int x; }; void operator >> (const YAML::Node& node, Matrix& matrix) { unsigned rows; node["rows"] >> rows; } int main() { std::ifstream fin("monsters.yaml"); YAML::Parser parser(fin); YAML::Node doc; Matrix m; doc["tableCenter"] >> m; return 0; } But I get terminate called after throwing an instance of 'YAML::BadDereference' what(): yaml-cpp: error at line 0, column 0: bad dereference Abort trap I searched around for some documentation for yaml-cpp, but there doesn't seem to be any, aside from a short introductory example on parsing and emitting. Unfortunately, neither of these two help in this particular circumstance. As I understand, the !! indicate that this is a user-defined type, but I don't see with yaml-cpp how to parse that.

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• Simple Android Binary Text Clock

  - by Hristo

  Hello, I want to create a simple android binary clock but my application crashes. I use 6 textview fields: 3 for the decimal and 3 for the binary representation of the current time (HH:mm:ss). Here's the code: import java.text.SimpleDateFormat; import java.util.Calendar; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class Binary extends Activity implements Runnable { Thread runner; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); if (runner == null) { //start the song runner = new Thread(this); runner.start(); } } @Override public void run() { TextView hours_dec = (TextView) findViewById(R.id.hours_dec); TextView mins_dec = (TextView) findViewById(R.id.mins_dec); TextView secs_dec = (TextView) findViewById(R.id.secs_dec); TextView hours_bin = (TextView) findViewById(R.id.hours_bin); TextView mins_bin = (TextView) findViewById(R.id.mins_bin); TextView secs_bin = (TextView) findViewById(R.id.secs_bin); SimpleDateFormat hours_sdf = new SimpleDateFormat("HH"); SimpleDateFormat mins_sdf = new SimpleDateFormat("mm"); SimpleDateFormat secs_sdf = new SimpleDateFormat("ss"); Calendar cal = Calendar.getInstance(); while (runner != null) { WaitAMoment(); cal.getTime(); hours_dec.setText(hours_sdf.format(cal.getTime())); mins_dec.setText(mins_sdf.format(cal.getTime())); secs_dec.setText(secs_sdf.format(cal.getTime())); hours_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) hours_dec.getText())))); mins_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) mins_dec.getText())))); secs_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) secs_dec.getText())))); } } protected void WaitAMoment() { try { Thread.sleep(100); } catch (InterruptedException e) { }; } }`

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• Trend analysis using iterative value increments

  - by Dave Jarvis

  We have configured iReport to generate the following graph: The real data points are in blue, the trend line is green. The problems include: Too many data points for the trend line Trend line does not follow a Bezier curve (spline) The source of the problem is with the incrementer class. The incrementer is provided with the data points iteratively. There does not appear to be a way to get the set of data. The code that calculates the trend line looks as follows: import java.math.BigDecimal; import net.sf.jasperreports.engine.fill.*; /** * Used by an iReport variable to increment its average. */ public class MovingAverageIncrementer implements JRIncrementer { private BigDecimal average; private int incr = 0; /** * Instantiated by the MovingAverageIncrementerFactory class. */ public MovingAverageIncrementer() { } /** * Returns the newly incremented value, which is calculated by averaging * the previous value from the previous call to this method. * * @param jrFillVariable Unused. * @param object New data point to average. * @param abstractValueProvider Unused. * @return The newly incremented value. */ public Object increment( JRFillVariable jrFillVariable, Object object, AbstractValueProvider abstractValueProvider ) { BigDecimal value = new BigDecimal( ( ( Number )object ).doubleValue() ); // Average every 10 data points // if( incr % 10 == 0 ) { setAverage( ( value.add( getAverage() ).doubleValue() / 2.0 ) ); } incr++; return getAverage(); } /** * Changes the value that is the moving average. * @param average The new moving average value. */ private void setAverage( BigDecimal average ) { this.average = average; } /** * Returns the current moving average average. * @return Value used for plotting on a report. */ protected BigDecimal getAverage() { if( this.average == null ) { this.average = new BigDecimal( 0 ); } return this.average; } /** Helper method. */ private void setAverage( double d ) { setAverage( new BigDecimal( d ) ); } } How would you create a smoother and more accurate representation of the trend line?

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• Migrating data from Plone to Liferay, or how could I retrieve information from Plone's Data.fs

  - by brandizzi

  Hello, all. I need to migrate data from a Plone-based portal to Liferay. Has anyone some idea on how to do it? Anyway, I am trying to retrieve data from Data.fs and store it in a representation easier to work, such as JSON. To do it, I need to know which objects I should get from Plone's Data.fs. I already got the Products.CMFPlone.Portal.PloneSite instance from the Data.fs, but I cannot get anything from it. I would like to get the PloneSite instance and do something like this: >>> import ZODB >>> from ZODB import FileStorage, DB >>> path = r"C:\Arquivos de programas\Plone\var\filestorage\Data.fs" >>> storage = FileStorage.FileStorage(path) >>> db = DB(storage) >>> conn = db.open() >>> root = conn.root() >>> app = root['Application'] >>> plone_site = app.getChildNodes()[13] # 13 would be index of PloneSite object >>> a = plone_site.get_articles() >>> for article in a: ... print "Title:", a.title ... print "Content:", a.content Title: <some title> Conent: <some content> Title: <some title> Conent: <some content> Of course, it did not need to be so straightforward. I just want some information about the structure of PloneSite and how to recover its data. Has anyone some idea? Thank you in advance!

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• Reinterpret a CGImageRef using PyObjC in Python

  - by Michael Rondinelli

  Hi, I'm doing something that's a little complicated to sum up in the title, so please bear with me. I'm writing a Python module that provides an interface to my C++ library, which provides some specialized image manipulation functionality. It would be most convenient to be able to access image buffers as CGImageRefs from Python, so they could be manipulated further using Quartz (using PyObjC, which works well). So I have a C++ function that provides a CGImageRef representation from my own image buffers, like this: CGImageRef CreateCGImageRefForImageBuffer(shared_ptr<ImageBuffer> buffer); I'm using Boost::Python to create my Python bridge. What is the easiest way for me to export this function so that I can use the CGImageRef from Python? Problems: The CGImageRef type can't be exported directly because it is a pointer to an undefined struct. So I could make a wrapper function that wraps it in a PyCObject or something to get it to send the pointer to Python. But then how do I "cast" this object to a CGImageRef from Python? Is there a better way to go about this?

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• Code Golf: Connect 4

  - by Matthieu M.

  If you don't know the Connect 4 game, follow the link :) I used to play it a lot when I was a child. At least until my little sister got bored with me winning... Anyway I was reading the Code Golf: Tic Tac Toe the other day and I thought that solving the Tic Tac Toe problem was simpler than solving the Connect 4... and wondered how much this would reflect on the number of characters a solution would yield. I thus propose a similar challenge: Find the winner The grid is given under the form of a string meant to passed as a parameter to a function. The goal of the code golf is to write the body of the function, the parameter will be b, of string type The image in the wikipedia article leads to the following representation: "....... ..RY... ..YYYR. ..RRYY. ..RYRY. .YRRRYR" (6 rows of 7 elements) but is obviously incomplete (Yellow has not won yet) There is a winner in the grid passed, no need to do error checking Remember that it might not be exactly 4 The expected output is the letter representing the winner (either R or Y) I expect perl mongers to produce the most unreadable script (along with Ook and whitespace, of course), but I am most interested in reading innovative solutions. I must admit the magic square solution for Tic Tac Toe was my personal fav and I wonder if there is a way to build a similar one with this. Well, happy Easter weekend :) Now I just have a few days to come up with a solution of my own!

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• What is the best way to send structs containing enum values via sockets in C.

  - by Axel

  I've lots of different structs containing enum members that I have to transmit via TCP/IP. While the communication endpoints are on different operating systems (Windows XP and Linux) meaning different compilers (gcc 4.x.x and MSVC 2008) both program parts share the same header files with type declarations. For performance reasons, the structures should be transmitted directly (see code sample below) without expensively serializing or streaming the members inside. So the question is how to ensure that both compilers use the same internal memory representation for the enumeration members (i.e. both use 32-bit unsigned integers). Or if there is a better way to solve this problem... //type and enum declaration typedef enum { A = 1, B = 2, C = 3 } eParameter; typedef enum { READY = 400, RUNNING = 401, BLOCKED = 402 FINISHED = 403 } eState; #pragma pack(push,1) typedef struct { eParameter mParameter; eState mState; int32_t miSomeValue; uint8_t miAnotherValue; ... } tStateMessage; #pragma pack(pop) //... send via socket tStateMessage msg; send(iSocketFD,(void*)(&msg),sizeof(tStateMessage)); //... receive message on the other side tStateMessage msg_received; recv(iSocketFD,(void*)(&msg_received),sizeof(tStateMessage)); Additionally... Since both endpoints are little endian maschines, endianess is not a problem here. And the pack #pragma solves alignment issues satisfactorily. Thx for your answers, Axel

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• SQL select descendants of a row

  - by Joey Adams

  Suppose a tree structure is implemented in SQL like this: CREATE TABLE nodes ( id INTEGER PRIMARY KEY, parent INTEGER -- references nodes(id) ); Although cycles can be created in this representation, let's assume we never let that happen. The table will only store a collection of roots (records where parent is null) and their descendants. The goal is to, given an id of a node on the table, find all nodes that are descendants of it. A is a descendant of B if either A's parent is B or A's parent is a descendant of B. Note the recursive definition. Here is some sample data: INSERT INTO nodes VALUES (1, NULL); INSERT INTO nodes VALUES (2, 1); INSERT INTO nodes VALUES (3, 2); INSERT INTO nodes VALUES (4, 3); INSERT INTO nodes VALUES (5, 3); INSERT INTO nodes VALUES (6, 2); which represents: 1 `-- 2 |-- 3 | |-- 4 | `-- 5 | `-- 6 We can select the (immediate) children of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1; We can select the children and grandchildren of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1 UNION ALL SELECT b.* FROM nodes AS a, nodes AS b WHERE a.parent=1 AND b.parent=a.id; We can select the children, grandchildren, and great grandchildren of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1 UNION ALL SELECT b.* FROM nodes AS a, nodes AS b WHERE a.parent=1 AND b.parent=a.id UNION ALL SELECT c.* FROM nodes AS a, nodes AS b, nodes AS c WHERE a.parent=1 AND b.parent=a.id AND c.parent=b.id; How can a query be constructed that gets all descendants of node 1 rather than those at a finite depth? It seems like I would need to create a recursive query or something. I'd like to know if such a query would be possible using SQLite. However, if this type of query requires features not available in SQLite, I'm curious to know if it can be done in other SQL databases.

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