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  • What are the real-world applications of huffman coding?

    - by jcyang
    I am told that Huffman coding is used as loseless data compression algorithm but also am told that real data compress software do not employ huffman coding,cause if the keys are not distributed decentralized enough,the compressed file could be even larger than the orignal file. This leave me wondering are there any real-world application of huffman coding? thanks.

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  • How to update NSMutableDictionary. My code doesn't work.

    - by dawatson833
    I've populated an array using. arrSettings = [[NSMutableArray alloc] initWithContentsOfFile:[self settingsPath]]; The file is a plist with the root as an array and then a dictionary with three three keys defined as number. I've also tried setting the keys to string. I display the values in the plist file on a view using. diaper = [[arrSettings objectAtIndex:0] objectForKey:@"Diaper Expenses"]; oil = [[arrSettings objectAtIndex:0] objectForKey:@"Oil Used"]; tree = [[arrSettings objectAtIndex:0] objectForKey:@"Wood Used"]; This code works fine, the values in the dictionary are assigned to the variables and they are displayed. The user can make changes and then press a save button. I use this code to extract the dictionary part of the array so I can update it. The assignment to editDictionary works. I've double checked the key names including case and that is correct. editDictionary = [[NSMutableDictionary alloc] init]; editDictionary = [arrSettings objectAtIndex:0]; NSNumber *myNumber = [NSNumber numberWithFloat:diaperAmount]; [editDictionary setValue:myNumber forKey:@"Diaper Expenses"]; myNumber = [NSNumber numberWithFloat:oilAmount]; [editDictionary setValue:myNumber forKey:@"Oil Used"]; myNumber = [NSNumber numberWithFloat:treeAmount]; [editDictionary setValue:myNumber forKey:@"Wood Used"]; In this example I've used a nsnumber. But I've also tried the xxxAmount field as part of SetValue instead of creating a NSNumber. Neither implementation works. Several strange things happen. Sometimes the first two setvalue statements work, but the last setvalue fails with a EXC_BAD_ACCESS failure. Other times the first setValue fails with the same error. I have no idea why the first two sometimes work. I'm at a loss of what to do next. I've tried several implentations and none of them work. Also, in the debugger how can I display the editDictionary elements. I can see editDictionary, but I don't know how to display the individual elements.

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  • Is it possible to parse a URL into it's composite components?

    - by Paul Alexander
    I'd like to parse an incoming URL into it's component parts for some pre-processing before passing it into the standard MVC routing logic. For example given your standard route {controller}/{action}/{id} and the URL /user/show/10 Is there a way to have the Routing system return a dictionary containing controller, action and id keys with their corresponding values?

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  • Strange Map Reduce Behavior in CouchDB. Rereduce?

    - by Tony
    I have a mapreduce issue with couchdb (both functions shown below): when I run it with grouplevel = 2 (exact) I get accurate output: {"rows":[ {"key":["2011-01-11","staff-1"],"value":{"total":895.72,"count":2,"services":6,"services_ignored":6,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":275.72,"count":1},"Review":{"total":620,"count":1}}}, {"key":["2011-01-11","staff-2"],"value":{"total":8461.689999999999,"count":2,"services":41,"services_ignored":37,"services_liked":4,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":4432.4,"count":1},"Review":{"total":4029.29,"count":1}}}, {"key":["2011-01-11","staff-3"],"value":{"total":2100.72,"count":1,"services":10,"services_ignored":4,"services_liked":3,"services_disliked":3,"services_disliked_avg":2.3333333333333335,"Revise":{"total":2100.72,"count":1}}}, However, changing to grouplevel=1 so the values for all the different staff keys should be all grouped by date no longer gives accurate output (notice the total is currect but all others are wrong): {"rows":[ {"key":["2011-01-11"],"value":{"total":11458.130000000001,"count":2,"services":0,"services_ignored":0,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"None":{"total":11458.130000000001,"count":2}}}, My only theory is this has something to do with rereduce, which I have not yet learned. Should I explore that option or am I missing something else here? This is the Map function: function(doc) { if(doc.doc_type == 'Feedback') { emit([doc.date.split('T')[0], doc.staff_id], doc); } } And this is the Reduce: function(keys, vals) { // sum all key points by status: total, count, services (liked, rejected, ignored) var ret = { 'total':0, 'count':0, 'services': 0, 'services_ignored': 0, 'services_liked': 0, 'services_disliked': 0, 'services_disliked_avg': 0, }; var total_disliked_score = 0; // handle status function handle_status(doc) { if(!doc.status || doc.status == '' || doc.status == undefined) { status = 'None'; } else if (doc.status == 'Declined') { status = 'Rejected'; } else { status = doc.status; } if(!ret[status]) ret[status] = {'total':0, 'count':0}; ret[status]['total'] += doc.total; ret[status]['count'] += 1; }; // handle likes / dislikes function handle_services(services) { ret.services += services.length; for(var a in services) { if (services[a].user_likes == 10) { ret.services_liked += 1; } else if (services[a].user_likes >= 1) { ret.services_disliked += 1; total_disliked_score += services[a].user_likes; if (total_disliked_score >= ret.services_disliked) { ret.services_disliked_avg = total_disliked_score / ret.services_disliked; } } else { ret.services_ignored += 1; } } } // loop thru docs for(var i in vals) { // increment the total $ ret.total += vals[i].total; ret.count += 1; // update totals and sums for the status of this route handle_status(vals[i]); // do the likes / dislikes stats if(vals[i].groups) { for(var ii in vals[i].groups) { if(vals[i].groups[ii].services) { handle_services(vals[i].groups[ii].services); } } } // handle deleted services if(vals[i].hidden_services) { if (vals[i].hidden_services) { handle_services(vals[i].hidden_services); } } } return ret; }

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  • how to send F2 key to remote host using python

    - by sagar
    i have to send F2 key to telnet host how do i send it using python...using getch() i found that this '<' used for F2 key but while sending its not working..i think there will be some way to send special function keys but i am not able to find it..if somebody knows please help me.thanks in advance

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  • How to pick a chunksize for python multiprocessing with large datasets

    - by Sandro
    I am attempting to to use python to gain some performance on a task that can be highly parallelized using http://docs.python.org/library/multiprocessing. When looking at their library they say to use chunk size for very long iterables. Now, my iterable is not long, one of the dicts that it contains is huge: ~100000 entries, with tuples as keys and numpy arrays for values. How would I set the chunksize to handle this and how can I transfer this data quickly? Thank you.

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  • how to install ipv4 via a cmd windows xp

    - by Kevin Babb
    I need to script a way to install IPV4 on windows xp the reason is i have many pc with a corrupt win sock registry so the fix Microsoft has is to delete the reg keys hklm/system/currentcontolset/services/winsock and winsock2 and then to run a netsch ip reset which creates the winsock2 part of the registry then the part i need to script is go to network adapter properties goto tcpip and install a new protocol and select tcp/ip and install it which uses the file c:\windows\inf\nettcpip.inf and then this creates the winsock part is there a way to script this part?? i have looked and cant find anything

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  • Infinite loop when adding a row to a list in a class in python3

    - by Margaret
    I have a script which contains two classes. (I'm obviously deleting a lot of stuff that I don't believe is relevant to the error I'm dealing with.) The eventual task is to create a decision tree, as I mentioned in this question. Unfortunately, I'm getting an infinite loop, and I'm having difficulty identifying why. I've identified the line of code that's going haywire, but I would have thought the iterator and the list I'm adding to would be different objects. Is there some side effect of list's .append functionality that I'm not aware of? Or am I making some other blindingly obvious mistake? class Dataset: individuals = [] #Becomes a list of dictionaries, in which each dictionary is a row from the CSV with the headers as keys def field_set(self): #Returns a list of the fields in individuals[] that can be used to split the data (i.e. have more than one value amongst the individuals def classified(self, predicted_value): #Returns True if all the individuals have the same value for predicted_value def fields_exhausted(self, predicted_value): #Returns True if all the individuals are identical except for predicted_value def lowest_entropy_value(self, predicted_value): #Returns the field that will reduce <a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29">entropy</a> the most def __init__(self, individuals=[]): and class Node: ds = Dataset() #The data that is associated with this Node links = [] #List of Nodes, the offspring Nodes of this node level = 0 #Tree depth of this Node split_value = '' #Field used to split out this Node from the parent node node_value = '' #Value used to split out this Node from the parent Node def split_dataset(self, split_value): fields = [] #List of options for split_value amongst the individuals datasets = {} #Dictionary of Datasets, each one with a value from fields[] as its key for field in self.ds.field_set()[split_value]: #Populates the keys of fields[] fields.append(field) datasets[field] = Dataset() for i in self.ds.individuals: #Adds individuals to the datasets.dataset that matches their result for split_value datasets[i[split_value]].individuals.append(i) #<---Causes an infinite loop on the second hit for field in fields: #Creates subnodes from each of the datasets.Dataset options self.add_subnode(datasets[field],split_value,field) def add_subnode(self, dataset, split_value='', node_value=''): def __init__(self, level, dataset=Dataset()): My initialisation code is currently: if __name__ == '__main__': filename = (sys.argv[1]) #Takes in a CSV file predicted_value = "# class" #Identifies the field from the CSV file that should be predicted base_dataset = parse_csv(filename) #Turns the CSV file into a list of lists parsed_dataset = individual_list(base_dataset) #Turns the list of lists into a list of dictionaries root = Node(0, Dataset(parsed_dataset)) #Creates a root node, passing it the full dataset root.split_dataset(root.ds.lowest_entropy_value(predicted_value)) #Performs the first split, creating multiple subnodes n = root.links[0] n.split_dataset(n.ds.lowest_entropy_value(predicted_value)) #Attempts to split the first subnode.

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  • Key Event Handling in Windows Services C#

    - by Yakov
    Hi! I want to create a windows service that may log pressed keys into files. For handling global key events I use hooks, hooks works great for desktop apps. But it doesn't work for the services. Is it possible to develop a windows service with key event handling? Developing on C#... Thanks for your time.

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  • What are the reasons *not* to use a GUID for a primary key?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • SQL Server unique constraint problem

    - by b0x0rz
    How to create a unique constraint on a varchar(max) field in visual studio, visually. the problem is when i try it: manage indexes and keys add columns I can only chose the bigint columns, but not any of the varchar(max) ones. Do I maybe have to use check constraints? If yes, what to put in the expression? Thnx for the info

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  • How to get right values from Views touch event

    - by Pinker
    I have a problem with implementing touch events on GLSurfaceView. Views size is 1280x696, because of android (tablet) status bar at bottom with soft keys, time etc.., (screen resolution is 1280x800), but OnTouchListener is receiving touch events with coords [646.0,739.0], and thus my gluunproject method fails to return correct values is there any way to return events that respect these boundaries? or how should I recalculate the position?

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  • Missing parameter error after running MySql query

    - by annelie
    Hello, I'm completely new to MySql and haven't used SqlDataSource with UpdateParameters before, so I'm probably missing something very obvious. When trying to update a record, the update does happen but then throws an error saying "'id' parameter is missing at the statement". So the query works and the database gets updated as it should, but an error is thrown afterwards. These are the update parameters: <UpdateParameters> <asp:Parameter Name="business_name" Type="string" Size="256" /> <asp:Parameter Name="addr_line_1" Type="string" Size="256" /> <asp:Parameter Name="addr_line_2" Type="string" Size="256" /> <asp:Parameter Name="addr_line_3" Type="string" Size="256" /> <asp:Parameter Name="postcode" Type="string" Size="32" /> <asp:Parameter Name="county" Type="string" Size="128" /> <asp:Parameter Name="town_city" Type="string" Size="256" /> <asp:Parameter Name="tl_url" Type="string" Size="256" /> <asp:Parameter Name="customer_id" Type="string" Size="16" /> <asp:Parameter Name="region_id" Type="Int16" /> <asp:Parameter Name="description" Type="string" Size="1024" /> <asp:Parameter Name="approval_status" Type="string" Size="1" /> <asp:Parameter Name="tl_user_name" Type="string" Size="256" /> <asp:Parameter Name="phone" Type="string" Size="50" /> <asp:Parameter Name="uploaders_own" Type="Int16" /> </UpdateParameters> Here's the update statement: UPDATE myTable SET business_name = ?, addr_line_1 = ?, addr_line_2 = ?, addr_line_3 = ?, postcode = ?, county = ?, town_city = ?, tl_url = ?, customer_id = ?, region_id = ?, description = ?, approval_status = ?, tl_user_name = ?, phone = ?, uploaders_own = ? WHERE id = " + id Here's the stack trace: [InvalidOperationException: 'id' parameter is missing at the statement] CoreLab.MySql.r.a() +775 CoreLab.MySql.r.a(Int32& A_0, ArrayList& A_1) +448 CoreLab.MySql.x.e() +398 CoreLab.MySql.x.o() +89 CoreLab.MySql.MySqlCommand.a(CommandBehavior A_0, IDisposable A_1, Int32 A_2, Int32 A_3) +1306 CoreLab.Common.DbCommandBase.ExecuteDbDataReader(CommandBehavior behavior) +310 System.Data.Common.DbCommand.ExecuteReader() +12 CoreLab.Common.DbCommandBase.ExecuteNonQuery() +64 System.Web.UI.WebControls.SqlDataSourceView.ExecuteDbCommand(DbCommand command, DataSourceOperation operation) +386 System.Web.UI.WebControls.SqlDataSourceView.ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues) +325 System.Web.UI.DataSourceView.Update(IDictionary keys, IDictionary values, IDictionary oldValues, DataSourceViewOperationCallback callback) +92 System.Web.UI.WebControls.DetailsView.HandleUpdate(String commandArg, Boolean causesValidation) +837 System.Web.UI.WebControls.DetailsView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +509 System.Web.UI.WebControls.DetailsView.OnBubbleEvent(Object source, EventArgs e) +95 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.DetailsViewRow.OnBubbleEvent(Object source, EventArgs e) +113 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +118 System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) +135 System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +175 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565 Does anyone know what I'm doing wrong? Thanks, Annelie

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  • RSA Encryption C#

    - by Ryan
    Hi guys, I have a class which in C# doing RSA encryption where I used the default RSACryptoServiceProvider class. But I have a concern regarding the following; If you have the word hello for an input and the encrypted string is returned as ABCDE, if you perform another encrypt operation on the input hello, using the same keys (public and private) for the RSA will the output be again ABCDE? Thanks in advance

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  • A Couple Android Soft Keyboard Questions

    - by Rich
    This is kind of a repost, and I apologize for any broken rules, but I have a couple of questions about the soft keyboard on Android phones: 1) I have an Android app with a couple different views (that the user switches between). How can I determine which is the current view?? I need to get the current view to execute the code that hides the virtual keyboard. 2) How can I check whether the virtual keyboard is currently being displayed (so I can filter the actions of my various hard keys)?? Thanks, R.

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  • How do I perform 'WHERE' on groups of rows?

    - by Drew
    I have a table, which looks like: +-----------+----------+ + person_id + group_id + +-----------+----------+ + 1 + 10 + + 1 + 20 + + 1 + 30 + + 2 + 10 + + 2 + 20 + + 3 + 10 + +-----------+----------+ I need a query such that only person_ids with groups 10 AND 20 AND 30 are returned (only person_id: 1). I am not sure how to do this, as from what I can see it would require me to group the rows by person_id and then select the rows which contain all group_ids. I'm looking for something which will preserve the use of keys without resorting to string operations on group_concat() or such.

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